Washington State University Extension

Garden Tips

Archive for January 2009


written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

I often get asked a wide variety of questions related to horticulture. It’s part of what makes my job so much fun. I’m a person who doesn’t like to “shoot from the hip” so when I don’t know the answer to a question, I take the time to do a little research. I’d prefer to give a correct answer so both the inquisitor and I can learn something. Here are four questions that I received in recent weeks…. with answers that I needed to look into.

QUESTION 1: Who is correct, the British or the Americans when it comes to referring to sweet corn as “corn” or “maize”? The British apparently use “maize” to refer to what we call “corn”.

The name “corn” is an old Anglo-Saxon word used as a general term to refer to any kind of cereal grain, but sometimes has been used to refer to wheat. In Australia, the use of “corn” is restricted primarily to sweet corn. In England “maize” is used to refer to sweet corn. In most other English speaking countries “corn” is not used as a general term to refer to what we call sweet corn, pop corn, or field corn. The word “maize” is used as a general term to refer to them. “Maize” is a native American word that is used more universally to refer to what we know in this country as corn.

This points out the difficulty in using common names to refer to any type of plant from country to country or region to region. What means “corn” in one place means something else in another place. The scientific name of corn is Zea mays L. ssp. mays. There are a number of important agricultural groupings of Zea mays L. subsp. mays including the Saccharata Group (sweet corn), the Everta Group (popcorn), the Indentata Group (dent corn), the Indurata Group (flint corn), and the Amlacea Group (flour corn).

Maize or “corn” is a native American plant. Scientists believe that primitive forms of maize first grew only in the Andes region of Peru. These forms mutated and crossed with other close relatives before and after the Peruvians transported it to Central America. By way of the Central American natives, these new types of maize found their way into what we now identify as the southwestern United States and then to northern and eastern parts of the country.

Maize eventually became a common crop of most Native American tribes. While the sugary characteristic of maize probably arose through mutation a number of times, it was not favored by most tribes. It wasn’t until the arrival of the Europeans in North America that sweet corn became desirable.

Which is right, corn or maize? I’m not sure, but some U.S. gardeners are starting to switch to the term of maize when talking about what the rest of us call corn. It’s less confusing when communicating with gardeners around the world.

QUESTION 2: What is crocosmia? My friend said I should put it in my flower garden.

Crocosmia is a member of the iris family and is native to South Africa. It’s also known by its common name of monbretia. There are different species and cultivars, some with small flowers and others with large flowers produced in multiple spikes from mid summer to autumn. Flower colors range from yellow to orange to red. The leaves are grass-like and similar to those on flowering iris.

These easy-to-grow plants do best in a well drained soil and are very drought tolerant. They require little fertilizer and do well in sunny sites, but might benefit from some shade with our hot summer conditions. Crocosmia flowers open a few each day, from the bottom of the flower stalks to the tip and are excellent as cut flowers.

Crocosmia are perennials and are hardy in USDA Zones 6 to 7. A mulch should be applied for protection from the cold in late fall, especially the first year after planting, In colder areas, they’re only considered semi-hardy and are grown in containers. Croscosmia arise from corms and tend to be fast establishing and multiplying. Some of the older cultivars such as ‘Lucifer’have been known to become too crowded within a year of planting and fail to flower the second year due to overcrowding.

Cultivars include ‘Meteor’ with small yellow flowers tinged with orange; ‘Red King’ small red flowers with orange-yellow centers;

Emily McKenzie

with large orange flowers; ‘Lucifer’ with large tomato red flowers; ‘Jenny Bloom’ a hybrid with orange buds that open into golden-yellow flowers; ‘Solfaterre’ a hybrid with chocolate brown leaves and apricot yellow flowers that is slower to multiply than other cultivars; and ‘Star of the East’ a hybrid with large bright orange flowers with starry centers of cream and maroon. This plant spreads more slowly than older cultivars.

QUESTION 3: When should I prune my hibiscus?

Do you have a rose-of-Sharon shrub or hardy hibiscus? Rose-of- Sharon (Hibiscus syriacus), a hardy shrub, is pruned in late winter or early spring before new growth begins. Prune out spindly canes and one-third of the oldest growth. The rose-of-Sharon blooms in the summer on new wood.

Hardy hibiscus (Hibiscus moscheutos) usually die back to the ground in the winter and are treated like a flowering perennial. After the tops die back in late fall or winter, trim the plant back to about twelve to eight inches above the ground. When new growth begins in the spring, you can encourage branching by pinching the stems back early in the growing season. While the rose-of-Sharon is a tall shrub, growing from six to eight feet tall, the various cultivars of the hardy hibiscus range in size from two to eight feet tall and two to six feet wide.

QUESTION 4: Is there something wrong with my sycamore tree? Lots of big pieces of bark came off of the trunk and main branches early in the summer. What’s up?

It’s natural for trees to shed bark as they grow, but usually the amount is very small and goes unnoticed. However, certain types of trees such as sycamore, London plane, and silver maple slough off their bark in larger pieces. Some years this shedding is particularly heavy and causes concern… and extra work cleaning it up. There is no need to worry if the bark only uncovers more bark beneath and not bare wood. With sycamore, the patch of bark underlying the shed portion is bright to olive green that later turns to a normal gray color.

Published: 12/25/2004 2:09 PM


written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

I was recently asked to speak to a combined class of sixth graders at Horse Heaven Hills Middle School. I wasn’t sure what I could talk about that might be of interest to the students, but I decided to talk about planting trees. After I finished giving my presentation I invited questions about trees or plants from the class. I was delighted to see how interested the students were in plants… almost everyone’s hands went up with a question. Here are just three of the questions that I received. I thought you might like to know the answers too.

QUESTION 1: It seems like our real Christmas trees dry up as soon as we set them up indoors. My parents are worried about fire and think that we should buy an artificial tree instead. I like real trees the best. They smell so good. Is there anyway to keep a real tree fresh for longer so we can get one without my parents worrying?

A fresh tree kept in water indoors can last for a month or more in good condition. There are four keys to keeping a real tree as fresh as possible and avoiding a fire hazard. First, start with a fresh tree. A tree that’s already dried out won’t last long no matter what you do.

Second, use a clean tree stand that holds at least four quarts of water. Once you set the tree up, it should be checked everyday and refilled as the water goes down. Never let the water level drop below the base of the tree. Research at WSU has shown that a fresh tree can take up as much as a full gallon of water the first day you set the tree up! Use only plain water with no special preservatives or additives in the water. WSU research has also proven that water additives, home concoctions or commercial products, have no benefit. In fact, some additives can actually reduce tree quality.

Third, cut off an inch or more off the base of the trunk just before you place it in the stand. This exposes the new xylem cells. These are the cells that take water up. When not covered with water, the xylem cells seal over within six hours and the uptake of water is obstructed. That’s why it’s always critical to keep the water level in your stand above the base of the tree. If allowed to dry out even once, water uptake will be slowed and your tree will start to dry out.

The fourth and final critical key to keeping a real tree as fresh as possible, is to situate the tree away from sources of heat such as hot air registers, baseboard heaters, wood stoves, and fireplaces.

QUESTION 2: My aunt has a weeping fig tree (indoor plant). She recently moved it from one place to another in her house and it dropped all its leaves. Should she move it back?

Weeping figs seem to drop their leaves if you cause them any sort of stress or change in their environment. In fact, it’s the most common problem with this indoor plant. If the new location adequately provides for its needs, then it will eventually stop dropping leaves and grow new leaves. The best environment for a weeping fig is one where they get lots of bright indirect sunlight, warm day (75 to 85 degrees) and night (65 to 70) temperatures. They also like high humidity and do best if their soil is kept moderately moist. Your aunt should move the weeping fig back if the new location fails to provide adequately for the plant’s needs.

QUESTION 3: We bought some of the lucky bamboo at the store. Can we plant it outdoors and why is it “lucky” ?

The plants sold by craft stores and other marketers are not really bamboo. Instead they are Dracaena sanderiana, a type of tropical plant that can be grown as a houseplant. Marketers selected this dracaena because it’s stem looks so much like bamboo and it’s easy to grow them in water. Other types of dracaena, such as Dracaena marginata, are also tropical plants that are grown as indoor plants. As a tropical plant, it can’t be planted outdoors and expected to survive the frosty temperatures of fall and winter.

As to why it’s “lucky,” I’m not sure. It could be because of the special significance of bamboo in various Asian cultures. Bamboo has long been a symbol of good luck or good fortune. Various marketers indicate that lucky bamboo is based on Chinese tradition, with different number of bamboo stalks having different meanings with the main ingredients for a happy life being “happiness, wealth, and longevity.” Different numbers and arrangements of the lucky bamboo signify different wishes for you, such as three stalks for happiness, five for health, six for prosperity, seven for good health or wealth, eight for thriving or prosperity, ten for completion and perfection, and twenty-one for a powerful blessing. A tower of lucky bamboo with 35 or more pieces “anchors fortune and lights up the future” and signifies more good things in life, a better life, or a promotion.

To care for lucky bamboo, their bases are placed in some sort of medium, such as clean aquarium gravel, clean sand, decorative pebbles, or marbles with water. They can also simply be sustained in plain water, covering the stem for an inch or less in water. Some Marketers don’t recommend adding any fertilizer to the water, others do. The water should be changed once a week. Don’t use water containing fluoride, as it’s toxic to dracaena.

The lucky bamboo do best with some indirect sunlight. They will grow roots on the stem bases, and more leaves from the sprouts that form at the top and sides of the stalks. However, their stalks will stay at the same height. They’re considered more of a decoration or curiosity, than a houseplant. Lucky bamboo can be maintained for quite a while in a home environment if they get some light and you regularly change their water.

You’ve probably noticed that some lucky bamboo for sale has fancy, curled stems and you may have wondered how they grew that way. It’s certainly not natural, as dracaena stems tend to be straight. Lucky bamboo farmers train the plants to grow that way. They do this by growing them horizontally on a table and covering three sides of the plant, so that only one side receives bright light. The plant then grows toward the light and the stem grows in that direction too. They then periodically rotate the stems to create a curl in the stem. Supposedly, it takes quite a while to create just one curl… an average of one and half years.

They were a great bunch of students Horse Heaven Hills Middle School and it’s my hope that they’ll stay interested in science and plants.

Published: 12/18/2004 2:10 PM


written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

Passionate environmentalists voice serious concerns over both water and air quality on earth, but another major concern for all of us should be the our soil quality. While water and air are critical to life… so is soil. It supports the plants we grow and is vital to our sustainability. “There is a universe that lies beneath our feet, yet most of us are not aware of it,” according to the editors of Partners a publication of the Conservation Technology Information Center.

Within the many micro and macro organisms found in a healthy soil, are special soil-borne fungi called mycorrhizas. The name means fungus (myco) root (rhiza). Micorrhizae are soilborne fungi that have a special relationship or association with plants. They live in association with plant roots, taking most of their needed nutrients, carbohydrates, vitamins, and amino acids from the roots. In return, the M serve as a secondary root system for the plant, sucking up water and nutrients from the soil and sharing them with the plant. It is definitely a mutually beneficial relationship and the more scientists study these fungi, the more they understand their importance to growing plants successfully.

There are three main types of Ms, ectoM, endoM, and ericoid M. The ectoM grow on the outside of the feeder roots, remaining outside the cells but “rooted” between root cells within the roots. It’s here that nutrient exchange takes place The endoM do penetrate cells and develop branched structures that look tree-like. These structures are where the nutrient exchange takes place between the plant and the fungus. Ericoid M are similar to the endoM, but only form the relationship with members of the ericaceous plant family, such as blueberry and rhododendron.

Why are the M important? Because they serve as secondary root system, absorbing water and nutrients from the soil and sharing it with the plant. The fine fungal strands or mycelia grow through the soil, developing a large surface area from which they can absorb the water and nutrients. In fact, they are more effective than the root system itself. A teaspoon full of healthy soil may contain several miles of M filaments… all helping provide the fungus and the plant with its needs.

Not only do they serve as a secondary and better root system for a plant, but they also help prevent infection of plant roots by pathogenic organisms, secrete enzymes which then convert some mineral nutrients into forms usable by the plant, provide greater drought resistance, stimulate root growth, and secrete a protein that improves soil tilth.

Some of our gardening practices can discourage development of M. Too much water means the development of lots of white succulent roots. These succulent roots generally are not colonized by M.

Published: 12/11/2004 2:11 PM


written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

Hopefully, all the Thanksgiving dinner leftovers have been used up. I still have some “leftovers” from other columns earlier in the fall. They didn’t get used up when I wrote those columns, but they’re too good not to share with you.


Ever wonder why flower bulbs planted in the ground don’t freeze over the winter? As you might guess, nature provides a way for bulbs to avoid cold temperature damage. The first is the insulation that soil provides. Even if the soil freezes, the soil temperatures where the bulbs are planted, typically don’t fall much below freezing, staying in the 29 to 30 degree Fahrenheit range.

Of course, there are also biochemical changes that occur within the bulb, according to the Netherlands Flower Bulb Information Center. With the onset of fall and cooler temperatures, starches stored in the bulb start to break down into glucose and other molecules. The glucose acts much like salt would by lowering the temperature at which water freezes. Also, layers of mulch and snow provide extra insulation during severely cold weather.

Have you ever noticed that the bulbs you planted two years ago or more come up much later than the first year they bloomed? For some reason, established bulbs tend to bloom about two weeks later than they do after their first year. For some, this is simply an interesting bit of trivia. For others, it’s important to know for when you’re adding bulbs to an existing planting and trying to coordinate bloom times for specific color combinations.


Where do gourds fit into the scheme of things when we’re talking about pumpkins and winter squash? Are they just dried out squash? The title of “gourd” is not an official botanical term. Instead, it generally refers to any member of the squash family that isn’t good to eat, dries well, and may be useful in some manner. As with any rule, there are exceptions. The Turk’s turban squash is considered by some to be a gourd, but it actually is a winter squash that’s both decorative and good to eat.

The bumpy, warty, colorful gourds that are so familiar to many are all in the group of Cucurbita pepo, along with some pumpkins, acorn squash, and all kinds of summer squash. The gourds are a subgroup or a “botanical variety” of this squash species. This subgroup includes pear, apple, orange, flat fancy, and the ugly warty-skinned fancy gourds.

In recent years, the lagenaria (Lagenaria spp.) or utilitarian gourds have become quite popular for use as birdhouses, crafting decorative items, and creating utilitarian items, such as ladles or bowls. Prized for their thick, hard shells when dry, this group includes bottle, siphon, calabash pipe, dolphin, club, and birdhouse gourds.

The third group of gourds are the luffas or vegetable sponges. The luffa gourds have elongated fruit with an outer shell that’s easily removed. Beneath the outer shell, the pulp is a tough and fibrous. When dried it can be used as sponges for scrubbing or made into ornamental items.


Is it safe to compost black walnut leaves, oak leaves, and pine needles in a compost pile? While you may have heard that one or all of these are bad to use in compost piles, don’t believe it.

Black walnut leaves do contain small amounts of the toxic plant chemical juglone. Juglone can cause the wilt and death of sensitive plants that come in contact with low concentrations of juglone. However, the juglone in black walnut leaves can be degraded in two to four weeks, according to Ohio State University Extension. That’s because this plant toxin degrades when exposed to air, water and bacteria. It breaks down completely within two months in a compost pile.

If one has volumes of black walnut leaves and wants to make sure there is no problem, the leaves can be composted separately and then tested for juglone toxicity by planting tomato seedlings in the compost. Tomatoes are very sensitive to juglone and will wilt and die if there are toxic levels of juglone present in the compost. Sawdust mulch, fresh sawdust or wood chips made from black walnut are a different story. They should not be used as a mulch around plants sensitive to juglone, such as blueberries, peppers, or tomatoes.

There is absolutely no reason why you shouldn’t use oak leaves or pine needles in a compost pile. The concern that they’re too acidic for adding to the soil is false. They should have no greater affect on soil acidity than other types of organic matter used in your compost pile. If they perchance do acidify the soil, that would be highly beneficial because most of our area garden soils are quite alkaline and the majority of garden plants prefer a slightly acid soil.

One drawback with oak leaves and pine needles is that they’re quite tough and break down slowly in the compost pile. If using them in a compost, be sure to chop up leaves first by shredding them in a shredder or running over them several times with your lawn mower. Smaller pieces of leaves and needles will decay more rapidly.

Also, take note that pine needles make great mulches for your garden. One reader let me know that she used pine needles as a mulch in her rose garden… based on my recommendation. It may have been circumstantial, but she notes that her roses are healthier than they have been in years and she has had much less of a problem with powdery mildew. It’s nice to hear from readers who have used my advice… successfully.

Well, I hope you enjoyed your leftovers.

Published: 12/4/2004 2:12 PM


written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

Did you take a sweater out this fall and find holes in it when there weren’t ones there when you put it away in the spring? Despite what you may have heard, the most likely culprits were carpet beetles…. not clothing moths, especially if it’s an acrylic sweater. Clothing moths are not a common pest in our region, but carpet beetles frequently find their way into closets, food cupboards, and other areas of the home.

There are two types of carpet beetles in our area, the varied carpet beetle and the black carpet beetle, with the varied carpet beetle being the most common. The varied carpet beetle is black with whitish uneven horizontal stripes. It’s a round little beetle that’s about 1/10 to 1/8 of an inch long. However, it’s not actually the adult beetles that cause the damage. They chow down on flower pollen outdoors. It’s their bristle-covered larvae that munch on and damage many things in our homes. These larvae are elongated, 1/8 to 1/4 inch in length, and brown and tan striped.

Carpet beetles like a protein diet, especially animal protein. In food cupboards, they’ll feed on products that contain protein… such as noodle mixes with cream or cheese sauce, dried milk, instant pudding, and cake mixes. They also are occasionally found in grain products. In closets they’ll feed on anything made from wool, silk, fur, hide, and feathers. Carpet beetles even feed on acrylic, linen, rayon, and cotton clothing that have been stored away without cleaning. Small spots of food or perspiration can leave a bit of protein for them to eat. They’ll also attack other items in your home… including dry dog and cat food, dead insects in light fixtures or window tracks, dog and cat hair, carpets, old book bindings, needlework made from wool or silk, animal trophies, and things made from bone and horn.

It’s the larvae that do the damage, but often neither the adult or larvae are detected in infested items. Instead, it’s the cast skins left behind when the larvae molt that are most frequently noted. If you find some of these cast skins, don’t panic. It’s not a sign of an unclean home. It just means you need to look for the source and clean it up.

The good thing about carpet beetles is that their populations don’t tend to build up quickly. Varied carpet beetles stay in the larvae stage for 220 to 630 days. They will be found in things that aren’t used very often… clothes that haven’t been worn for a while or food that got “lost” in the back of the cupboard.

Once discovered, an infestation can usually be cleaned up by getting rid of their food. This is as simple as throwing out any infested food products and thoroughly cleaning the cupboard. Do this by vacuuming cracks and crevices and then wiping the surfaces with soap and water. If it’s an item of clothing, it should be cleaned in the appropriate manner.

In some cases, you may have something that you can’t clean but don’t want to throw out, such as an ornament made from wool, an insect collection, or a trophy animal head. If it isn’t too big, the item can be placed in the freezer (below 32 degrees) and then removed and thawed. Repeat this three times at two day intervals. That will usually kill any carpet beetles and their larvae.

You can help prevent carpet beetle problems, by not storing food in your cupboard for long periods. Try to use up products in a timely manner. Throw them out if you don’t plan to use them again. If they’re unopened and still good, give them to a nearby food bank. Food that you want to keep for longer periods should be stored in the freezer or stored in a tightly sealed containers. Before putting winter clothing away for the spring and summer months, clean them as recommended by the manufacturer. Periodically check stored clothes and susceptible items for signs of infestation, especially if stored in an undisturbed area of the home.

You may wonder why we’re talking about “rug bugs” in a gardening column. One reason is that they may be brought into the house from the garden on cut flowers. During the warm, sunny days of summer the adults feed on the pollen of a variety of garden plants, such as spirea, dogwood, daisies, asters, and achillea. Attracted to light at night, the beetles can also find their way into homes through windows, doors, and other openings.

The other reason why I’m talking about carpet beetles is that, like it or not, I ‘m often asked about household pests and their control. With the onset of cold weather, some of you are probably finding holey clothing. Now you know to blame carpet beetles… not clothing moths.

Gardening Word of Caution: A gardener called me recently about the bad rash with blisters that she had developed after trying to remove snow-on-the-mountain from her garden. Another time, two young boys had played with the plant, putting it in their mouths, but not eating it. They developed serious blistering in their mouths. Plants in the euphorbia family have a milky latex sap that can cause skin rashes and blisters. This includes crown-of-thorns (houseplant), poinsettia, and snow-on-the-mountain (a flowering groundcover perennial). When pruning, pulling, cutting, or weeding around snow-on-the-mountain, it’s best to keep your skin covered and wear protective gloves and goggles to protect yourself from the sap. If you get the sap on your skin, wash it off right away.

With the holidays, many of us will have pretty poinsettias in our homes. While the poinsettia is not poisonous as it was once thought, it’s sap can be irritating to some. Keep them away from inquisitive children and pets.

Published: 11/27/2004 2:12 PM


written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

When some people pick out a tree for their landscape, they don’t think about its overall mature form, the bark, or how it looks the rest of the year. They want an impressive flower display in the springtime. Sure a tree will look nice in the spring if it has pretty flowers, but it’s the form and bark that I most appreciate. After all, it’s what we look at most of the year. Good fall color in bright yellow, orange or red is also another big plus for me.

Some trees are gorgeous when in flower, but really don’t do much for the landscape the rest of the year… in my opinion. The purple leaf or ‘Thundercloud’ plum has a gorgeous display of flowers in the spring, but the rest of the year the tree has those awful purple leaves and gnarly branch growth. Yes, I confess that I have a personal dislike of purple-leaved trees, but even if it had green leaves I wouldn’t think of this tree as a winner in a beauty contest… of course “beauty is in the eye of the beholder.” The same goes for English hawthorn. It looks very pretty covered with tiny pink bouquets of flowers in the spring, but the crowded twiggy branch growth and threatening thorns are two detracting features in a landscape. Maybe if the plum and hawthorn had interesting bark, I might like them more.

Here are a few trees that I would like in my landscape.

River Birch: While most people desire the white bark of the European white birch or the canoe birch, I prefer the river birch. The river birch (Betula nigra) has peeling apricot colored bark. The ‘Heritage’ cultivar has lighter, almost white bark. This birch is resistant to bronze birch borer and does fairly well in our climate. I like this tree so much, I planted three of them in my front yard. They’re situated in a triangle design eight feet apart… to give the feel of a clump or glade, without the problems of them being crammed into one hole. Their shiny green leaves stand up well to full sun and wind, turning a nice yellow in the fall. I enjoy them all year long.

The species reaches a height of 70 feet and is pyramidal when young, becoming more rounded as it grows older. Other cultivars of river birch include ‘Dura-Heat’ TM that’s smaller than the species and has yellow fall color;

Little King

is a low-branched dwarf with white bark that grows only 8 to10 feet tall; and ‘Tecumseh Compact’ TM with compact, pendulous growth tops out at 12 feet in height.

Lacebark Elm: Now don’t confuse this tree with the trashy Siberian elm (Ulmus pumila) that sprouts up as a weed tree all around us. The lacebark elm or Chinese elm (Ulmus parvifolia) is quite different. It’s beautiful. Its form varies from upright to weeping, depending on the cultivar. Its flowers (produced in late summer) are inconspicuous, but it has yellow to purple fall color. Its most fetching and remarkable characteristic is the bark. As the tree matures, the bark starts to slough or peel off in small patches, creating a mosaic of green, gray, orange, and brown. It’s quite lovely.

The tree does well in harsh, hot climates like ours and is fairly quick growing. It’s biggest drawback are the invasive, shallow roots that can become a problem as the tree grows bigger and older. Because of this, they should not be planted in locations where the roots can cause a problem.

Hardiness varies with the cultivar, with many of them suitably hardy in our region.


would be perfect for the smaller landscape with its compact growth habit, growing only 6 feet

tall. Most of the cultivars reach a mature height of 40 to 50 feet, but there is one very small cultivar,


. It has miniature leaves and grows only to a height of one foot… it’s used for creating bonsai. ‘Drake’ and the weeping form ‘Sempervirens’ are not considered hardy in our region.

I’d like to have a lacebark elm in my landscape, but they’re not easy to find in our region, especially the improved hybrids developed by the National Arboretum. These hybrids have been bred to resemble the American elm which has been basically wiped out in the U.S. by Dutch elm disease, to which the lacebark elm is resistant.

Maples offer all sorts of interesting bark for our appreciation. One in particular, the paperbark maple, Acer griseum, finds its way into some local landscapes. It has very interesting rusty or cinnamon brown bark and reddish-brown fall color. The species tree grows to a manageable 20 feet. It ‘s a nice small tree with a rounded crown. A hybrid cultivar ‘Ginzam’ (also known as ‘Gingerbread’) is taller at 30 feet and has a more upright oval shape at maturity. It also has nice brown bark and orange to red fall color.

These are just a few of the trees with interesting bark. Other notables include:

– Acer palmatum ‘Sangokaku’, the coral bark Japanese maple, with coral red bark and yellow fall color

– Acer pensylvanicum, the striped maple, with green and white striped bark when young and yellow fall color

– Acer rufinerve, the snakebark maple, with distinctly striped bark and red to yellow fall color

– Parrotia persica, Persian parrotia with exfoliating bark and yellow, orange, and red fall color

– Betula lenta, sweet birch, with an amazing shiny, reddish brown bark

– Plantanus x acerifolia , the London planetree or sycamore, with exfoliating bark that creates a gray, white, and olive green mosaic pattern and no fall color

Published: 11/20/2004 2:12 PM


written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

We certainly all know it’s traditional to have berry pie after our Thanksgiving dinner. Wait a minute… berry pie? I bet you thought it was pumpkin pie. Well, you’re right and I’m right. That’s because botanically, pumpkins are classified as berries. They have a fruit that develops from a single pistil (the female part of the flower) and they have seeds that aren’t enclosed in a hard outer covering or “stone. ”

Pumpkins and the rest of the squash family are “native American” plants having originated in South, Central, or North America. They ‘ve been grown as crops for thousands of years. Long before Europeans discovered the existence of the New World, native populations were cultivating squash as one of their main food crops. In fact, the name “squash” comes from an Algonquin word “asku’tasquash” meaning “food eaten raw.”

There are a little over 25 species of plants in the squash and melon family, known as the Cucurbita family. A number of cultivars within four of these 25 species are commonly referred to as winter squash. The designation of “winter squash” generally means the fruit has a hard skin, dry flesh, and fairly long storage life. Many winter squash have orange flesh that is traditionally prepared and eaten during the fall and winter months. “Summer squash” have tender skin, moist flesh, and don’t store well. They’re best eaten when very young and fresh. “Pumpkins” are generally winter squash that are round and orange.

Unless you’re a botanist, the following botanical discussion may seem a bit boring and pedantic, but it’s important to gardeners, squash growers, and pumpkin fanciers… so please bear with me. Here’s a brief look at each of the four main types of winter squash.

Cucurbita maxima: Within this species you find the traditional rather large winter squash… Hubbard,, banana, buttercup and the colorful turban squash, as well as “mammoth pumpkins.” The species is characterized by rounded, mostly unlobed leaves; fleshy round stems; and a corky peduncle (that’s where the stem is attached to the fruit).

Cucurbita pepo: This species includes summer squash so familiar to home gardeners, including zucchini, yellow straight neck, yellow crookneck, spaghetti, cocozzelle, and patty pan (scallop) squash. It also includes the jack-o’-lantern pumpkins; sugar pumpkins; most of the bumpy, warty gourds used for autumn decorations; acorn squash; and the more recent winter squash introductions ‘Sweet Dumpling,’ ‘Delicata,’ and ‘Tatume’. This species has hard, 5-angled prickly stems; a strongly flared peduncle; and bristly, lobed leaves.

Cucurbita moschata: You can tell this group by their hard, angular stems with soft hairs and their white-marked, shallowly lobed, hairy leaves. The cultivars included in this group are butternut, some cushaws, Cuban, calabaza,, and ‘Tahitian’ squash.

Cucurbita mixta: The angled stems of this group are hard with soft hairs. The peduncle is five angled, not flared, but with a corky swelling at the base. The shallowly lobed leaves are smooth or just a little hairy and usually have white blotchy markings. This group includes most cushaws, sweet potato squashes, and potato pumpkins.

So now that we’ve talked about different types of winter squash….what’s the difference between a pumpkin and a winter squash? The designation of “pumpkin” is not a botanical term. Pumpkin purists insist that true pumpkins are the Cucurbita pepo pumpkins, such as ‘Connecticut Field,’ ‘Jack-o’-Lantern,’ ‘Autumn Gold,’ ‘Big Tom,’ or ‘Early Sweet Sugar.’ They have bright orange skin and the characteristic hard woody, furrowed stems of C. pepo.

Others less concerned with semantics consider any winter squash that’s sort of orange and somewhat round to be a pumpkin. Such is the case with most local, state and national big pumpkin championships. The gargantuan pumpkin winners are always cultivars of Cucurbita maxima. The prominent mammoth cultivars include ‘Atlantic Giant,’ ‘Big Max,’ ‘Big Moon,’ ‘Hungarian Mammoth’ and ‘Show King.’ The C. maxima “pumpkins” are generally more yellow than orange and most end up a bit more lopsided than round because of their great size.

This year’s winner of the “Safeway World Championship Pumpkin Weigh-Off” was a C. maxima ‘Atlantic Giant’ pumpkin weighing in at 1,229 pounds. It measured 13 feet, seven inches around! The winner’s grower is Joel Holland, a retired Washington state firefighter from Puyallup, Washington. Holland received a prize of $6,145…. $5 for every pound of pumpkin.

When Thanksgiving rolls around in a couple of weeks, many of us will finish a great dinner with the conventional piece of pumpkin pie, but we probably won’t be eating C. pepo or C. maxima pumpkins. Instead, we’ll be eating Cucurbita moschata processing pumpkins, such as ‘Dickinson Field,’ ‘Buckskin,’ or ‘Kentucky Field.’ These pumpkins tend to look more like tan-colored watermelons. They have dark orange, fine-textured, dry flesh. If you’ve ever tried to make pumpkin pie from scratch, the results may have been disappointing. The flesh of the traditional jack-o’-lantern pumpkins is of poor quality for baking and eating.

Oh, I almost forgot to mention the littlest pumpkins marketed in recent years for fall decorating. These little pumpkins are members of Cucurbita pepo. They were developed in Asia and are bright orange, somewhat squat in shape with deep sutures. Most American consumers consider them a gourd. They’re quite a bit like gourds in that they are decorative, small, and last a long time. However, unlike gourds they’re said to be good baked, stir-fried, or pureed. Cultivars include ‘Jack-B-Little,’ ‘Jack-B-Quick,’ and ‘Munchkin.’

This entire squashy pumpkin discussion may cause you to ask “so what?” Pumpkin growers and gardeners who save their seed need to know the difference between the different species. That’s because different cultivars of squash within the same species can cross pollinate. The seed resulting from such a cross often results in some strange looking squash that lack the desirable appearance or characteristics of either parent. Big pumpkin growers typically save the seed of their largest specimens in the attempt to groom bigger and better offspring for the next year. If their giant pumpkins cross with some other cultivar of the same species, it can spell disaster.

If nothing else, you can have an interesting discussion of pumpkins and squash when Thanksgiving dinner is over. Enjoy your berry (pumpkin) pie!

Published: 11/13/2004 2:13 PM


written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

It’s about the time of year when we gardeners start thinking about how our plants will stand up against the winter cold. Will my roses make it through the winter? Will my tender perennials survive? Will my cedar come through the winter unscathed once again? It’s no wonder gardeners talk a lot about the weather, it’s so important to our gardening success. I’ve heard that some long range forecasters are predicting a fairly mild winter with temperatures slightly above normal for our part of Washington, so perhaps we don’t need to worry… but those forecasters might be wrong!

Plants are said to be “hardy” in a region if they can withstand the average minimum temperatures commonly encountered there. The main factor involved in a plant’s survival is its inherited ability to withstand winter cold. It’s in their genes.

Hardy plants go through physiological and biochemical changes during the fall that allow them to survive cold temperatures during the winter. These internal changes are induced by two environmental cues that occur in late summer and early fall… shorter days and cooling temperatures.

Scientists call the internal process a plant goes through to achieve hardiness “acclimation”. As the days grow shorter and the temperatures gradually lower, a plant acclimates and achieves its “maximum hardiness” in mid-winter. In late winter, plants lose hardiness through a process called “deacclimation”. Deacclimation occurs in response to lengthening days and warmer temperatures.

Damage to plant tissues or “winter injury” can occur due to abnormal or untimely temperature fluctuations… or due to a gardener’s ill-advised plant selection or poor gardening habits. Severe cold temperatures in the fall, before plants have been able to achieve their maximum winter hardiness, may cause injury. This occurred in our region in October of 2003 and also in October of 2002. Some plants sustained injury from the severe cold because the temperatures dropped to single digits immediately after a spell of very balmy fall weather… long before the plants had become acclimated and able to withstand such low temperatures. English walnuts and flowering cherry trees were two plants that sustained severe damage.

Plant selection is important too. Plants are said to be “hardy” in an area if they can withstand the average minimum low temperatures for that region. The USDA has developed a map with hardiness zones based on average minimum temperatures. Plants are then rated as to the coldest zone in which they can be grown without worry of winter injury. Our area is primarily in USDA Zone 6 with an average minimum temperature of 0 to -10 degrees Fahrenheit, although there are some warmer spots that are in Zone 7 with a minimum of 1 to 10 degrees Fahrenheit. Nursery care tags will often indicate a plant’s hardiness by providing the USDA Zone information. There are also numerous references that provide hardiness zone designations for specific plants… trees, shrubs, and perennials.

The Sunset Publishing Company (Sunset Western Garden Book and Sunset Magazine) also rate plants for their planting suitability in areas and place them in zones. However, their “climate” zones are based on minimum and maximum temperatures, soil conditions, precipitation, and other environmental growing conditions. Our region is located in Sunset Zones 2 to 3.

Gardeners should also be careful not to stress plants or stimulate plant growth late in the season. Plants stressed from drought, heat, insect infestations or disease are more susceptible to cold temperature damage. Plants stimulated to grow by pruning, fertilizing, and watering heavily late in the growing season will not acclimate well and will be more vulnerable to injury.

So what can a gardener do to protect plants from low temperature damage during the winter? Here are some tips.

1. Select plants that are fully winter hardy in our region… Zone 6. A “borderline” plant that’s only hardy to Zone 7 or 8 may survive several mild winters that might occur in succession. However, it will eventually succumb to damage that will occur in one of our colder winters. Exceptions can be found if plants are situated in milder micro-climates that occur in some spots due to topography, proximity to the river, and exposure in the landscape.

2. Don ‘t fertilize your trees, shrubs, and perennials in late summer or early fall. This stimulates growth that won’t be ready for winter. Note: If tree and shrub roots are located in the lawn area and you’re applying the recommended fall fertilizations for your lawn, you’re probably unwittingly also fertilizing your trees and shrubs.

3. As weather cools and water demands on plants decrease in late summer and early fall, be sure to reduce your watering. Heavy watering in early fall can delay the acclimation process.

4. It’s okay to remove dead, injured, or diseased portions of the plant at any time, but don’t prune your plants heavily in the fall. If you need to do considerable shaping or removal of healthy, live portions of the plant, wait until the plant is dormant. For roses, it’s okay to shorten extra long canes to avoid damage in windy weather, but any extensive pruning should wait until spring.

5. Tender perennials, roses, trees, and shrubs can be mulched to insulate their roots from severe cold temperatures, but don’t apply the mulch too early. Plants need to be exposed to cooler soil temperatures as part of the acclimation process. Don’t apply protective mulches until at least the middle of November.

6. Winter drought can also be a problem in our region. Overcast and sometimes foggy weather can give the illusion of moist conditions. However, we often experience mild, dry, and windy weather that can lead to winter drying and drought stress. If conditions remain dry and mild, it helps to water trees, shrubs, roses, and perennials every three to four weeks.

I don’t know if the weather forecasters are right, but it’s always good to be prepared for cold weather… although I’d much prefer a mild winter! How about you?

Published: 11/6/2004 2:13 PM


written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

Have you watched that show on television called “Mythbusters”, where they test urban myths and legends to see if they could possibly be true? It’s an updated way to look at science and test the truth of modern folklore. Mr. Wizard was never like this! Unfortunately, this show has ignored an important area of modern myths… gardening myths and anecdotes. Gardeners could benefit from a little “mythbusting” or scientific testing of the validity of some garden myths floating around out there.

For instance, one of the most recent myths to surface in the gardening world is that of compost tea. If you haven’t heard of this before, you’re probably wondering what in the world is compost tea. Compost tea is made by soaking finished compost in water and then using the “brewed” tea or liquid portion for fertilizing plants. This can be done by making a “tea bag” out of a nylon stocking and stuffing it with compost. A fine mesh animal feed bag can also be used. The “tea bag” is soaked in a five-gallon bucket or small barrel partially filled with water. The compost is steeped for several days with periodic stirring or agitation to get a better brew.

Once brewed, the tea has traditionally been used as a liquid organic fertilizer. However, numerous popular sources now tout compost tea’s powerful anti-microbial components capable of fighting various plant diseases that attack plant leaves and fruits. Many of the sources promoting compost tea as a way to control plant disease are also trying to sell gardeners something… their own brews, compost additives, or special aerating equipment for making a more sophisticated, better quality tea.

The problem with all this is that the effectiveness of compost teas seems to be primarily anecdotal, not based on sound research principles. Dr. Linda Chalker-Scott, WSU Extension Horticulturist at WSU Puyallup, has searched peer reviewed scientific literature for research reports on the effects of compost tea for controlling plant diseases. It appears that non-aerated compost teas may be useful in suppressing some types of plant pathogens, but aerated compost teas have “no scientifically documents effect as pathogen suppressors”.

Gardeners probably already know that there is a great deal of variability in compost because the materials composted depend on their availability and will usually vary from season to season. Also, some gardeners are more skilled or dedicated to composting than others. What it “boils down to” is that just as there is great variability in compost from batch to batch, there is great variability in compost tea from batch to batch. While some compost teas may contain large numbers of pathogen fighting microbes or pathogen fighting chemical compounds, others may not. More research is still needed before gardeners start using compost tea for application to plants for control of plant diseases or for foliar “feeding” of plants.

A new myth might be surfacing… using aspirin to control plant diseases. I read about this recently in a newsletter that came across my desk. Apparently a solution containing aspirin is surfacing as a home remedy for powdery mildew control on roses. Whenever a new gardening myth or home remedy surfaces, gardeners wondering about its “truth” should subject it to a set of criteria to determine its validity. Anecdotal recommendations shouldn’t be relied upon… even if you see it in print.

1. If you read about it in print, are articles that appear in that magazine, newsletter, or journal reviewed and critiqued by independent experts in the field? If not, scientific verification of the claims should be sought elsewhere.

2. Consider who is writing the article or a book? Is it a gardening author or book published by the popular press or is it published by an academic or scientific publishing house? It’s not uncommon to see the popular press pass on anecdotal information or home remedies based on pseudoscience.

3. When experimentation has “proven” a premise, such as the use of compost tea to suppress disease, has the experiment been proven elsewhere with the same results? A premise or hypothesis becomes the “truth” only if subsequent studies have failed to disprove it.

4. Ask yourself about the motives of the authors. Are they trying to sell you something or perhaps trying to sell their publication? This has been the case with compost teas where the promoters say that aerated compost tea is better… and they just happen to sell compost tea aerating equipment.

Now back to the aspirin. I saw this in a gardening newsletter written by local gardeners and published by their club. It’s certainly not a scientific journal reporting on a scientific study. They’re simply passing on a home remedy that other gardeners have tried and believe to be effective. The aspirin producer is not touting their product as a plant disease control product. No one is trying to sell anything.

On the surface this home remedy may seem like myth, but it actually has some scientific basis. When plants are attacked by and insect disease, they respond by producing certain chemical compounds which can improve a plant’s resistance to the pest or they can stimulate the production of such compounds.

In plants, this disease resistance or immune-type response is stimulated by salicylic acid, the ingredient in aspirin. The salicylic acid signals the plant to make a variety of defense related proteins. Research has shown that acetylsalicylic acid (aspirin) applied to plants can induce resistance to some diseases.

One chemical company now produces a salicylic acid derivative that induces systemic resistance response in plants. It’s called Actigard and is registered for use on some commercial vegetable crops for control of certain diseases. When enough aspirin was used in experiments to induce a systemic response, plant damage generally occurred. Actiguard is supposedly gentler on plants.

The amount of aspirin recommended in the newsletter may not harm plants, but I would bet that it’s the water spray and possibly the additives of soap or horticultural oil recommended as part of the aspirin spray mixture that actually provide powdery mildew control. Research has shown that a regular application of water can be effective in controlling powdery mildew. Imagine that!

Published: 10/30/2004 2:14 PM


written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

I was in the Seattle area last week and was impressed with the absolutely gorgeous fall color in many of the commercial and residential landscapes. You couldn’t have asked for more brilliant red and vibrant yellow leaves. Growing up in the northeast part of the country, I miss the visual treat of the autumn leaves in fall. While it can’t compete with the northeast, you can find some very nice fall colors in our area. In fact, I came home from my trip to find the red maple in my yard a dazzling red. It was especially spectacular when lit from behind by the setting sun.

To get more reds, oranges, and purple fall color in local landscapes, we need to plant trees that can be relied upon to exhibit good fall color. Here are a few of the trees and shrubs you might want to consider.

Red Maple (Acer rubrum) – Red maple is at the top of most lists when bright red fall color is desired. It’s a tree well adapted to harsh conditions, even our city landscapes. It’s also one of the most dependable trees when it comes to fall color. You can’t go wrong with a red maple and it’s one of my favorite trees.

There are a number of red maple cultivars (cultivated varieties) that have been selected by nurserymen for their exceptional fall coloring. ‘October Glory’ is very popular in our area. It has deep red to red-purple fall color, as well as glossy green leaves during the summer. It develops into a 40

tree with a rounded crown. ‘Red Sunset’ is a vigorous growing tree that turns brilliant shades of red in the fall. It grows to 45

tall and has a strong branching pattern. ‘Autumn Flame’ is sure to have some of the brightest red fall color you could want. It grows into a compact, rounded tree that’s 35

tall and 35

wide. For formal landscapes or narrow places you can still get great fall color from ‘Scarlet Sentinel.’ It’s an upright red maple with a compact habit, growing 40

tall and only 20


Sometimes hybrids of the red maple are listed as “red maples.” These hybrid cultivars, such as ‘Autumn Blaze’, ‘Armstrong’ and ‘Celebration’ are actually crosses between the red maple and silver maple, Acer saccharinum. They are more correctly called cultivars of Acer x freemanii, the Freeman maple.

Red Oak (Quercus rubra) – Red oak is another of my favorite trees. It’s relatively fast growing for an oak, growing up to two feet a year. In autumn, it shows off with rich deep red to russet brown color that adds to the fall landscape. When young, it has a pyramidal shape and then becomes more rounded with age. At maturity it’s 60

to 75


Sweetgum (Liquidambar styraciflua) – While the botanical name of this plant sounds more like a disease than a plant name, it’s a tree that does fairly well in our area and provides excellent red to burgundy fall color. It grows to a height of 60

to 75

tall with a pyramidal shape. While the spiked ball-shaped fruit can add a decorative flair in late fall and winter, many gardeners find them objectionable. Surface roots that lift sidewalks and driveways are often a problem with sweetgum trees.

‘Cherokee’ is an extremely cold hardy sweetgum that’s virtually seedless. ‘Rotundifolia’ is a distinctive seedless sweetgum with shiny, lobed leaves . It grows to 75

tall and is narrower and more pyramidal in shape. ‘Happidaze’ is another fruitless form and has a deep maroon fall color. ‘Festival’ sounds interesting with its narrow form and a golden fall color with shades of peach and red. ‘Variegata’, the golden sweetgum, has light green leaves that are spotted and streaked with yellow. When it colors up in the fall, the yellow areas supposedly turn pink and the green areas turn red.

Katsura (Cercidiphyllum japonicum) – The katsura tree isn’t widely planted in our area, but some local gardeners are giving them a try to see how they’ll do here. So far they’ve been slow to become established, but hopefully they’ll be another tree that we can add to our fall color pallette. I suspect they would do best planted on the north side of a structure with some shade; mulched with bark or compost; and kept slightly moist through the summer. It grows to a height of 40

to 60

and is pyramidal when young. As it matures, the crown becomes more rounded with a wider spread. In the spring the leaves are first purplish and then turn blue-green.

The katsura tree is most amazing in the fall. It’s heart-shaped leaves turn multicolors of orange, apricot, and yellow. The leaves also give off a sweet fragrance in the fall that’s been described by some as smelling like caramel, apricot, or brown sugar. The species grows to a height of 40

to 60

with a wide spreading crown when mature, but it’s pyramidal shaped when young. ‘Heronswood Globe’ is a more compact form with a rounded globe-shaped crown 15

to 20

wide. ‘Pendulum’ is a weeping form that has been grown in culture for over 300 years at Buddhist temples in Japan, but it’s hard to come by in the nursery trade. ‘Strawberry’ is a new cultivar from Holland. It has “strawberry” fall color and fragrant fall leaves.

Sourwood (Oxydendrum arboreum) – Sourwood is another tree that isn’t planted much in our area, although you can find it growing in western Washington landscapes. Here is a tree that provides more than just bright scarlet fall color, it also produces attractive droopy white flower clusters in late summer. The flowers look a bit like lilies of the valley and the tree is often called the “Lily of the Valley” tree.

This is one tree that some gardeners might want to try, but you’ll want to put it in a protected, somewhat shady location,. It’s in the same family as blueberries and rhododendrons, and like its cousins, it requires an acid, organic soil to grow well. It also should be kept moist through the summer. If you try this tree, plant it in a shrub bed and amend the soil in the bed with compost and peat moss before planting. Mulch with an organic mulch.

Published: 10/23/2004 2:15 PM

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