Washington State University Extension

Garden Tips

Archive for April 2011


written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA


New and experienced gardeners are always anxious to get their vegetable garden planted in the spring, but warm season crops should not be planted until the danger of frost is past and the soil has warmed up. Recent cool and frosty nights are a reminder that patience is truly a virtue. Wait to plant warm season crops until both warmer days and nights prevail and after the last average date of frost (May 1-15 in our region). Warm season crops include tomato, pepper, eggplant, squash, melon, watermelon, cucumber, potatoes and beans. Planting early and providing frost protection doesn’t really help these plants get a jumpstart on the season because they simply don’t grow when soil and air temperatures are cold.

Cool season crops that thrive in cool early spring weather and soils include lettuce, onions, peas, radishes, rhubarb, and spinach . These crops are planted as soon as you can get outside and work in the garden, typically around the beginning of April in our region. If planted too late, they will grow but will usually “bolt” or start to flower when hot weather arrives, affecting their production and eating quality.

As soon as the soil warms up a bit, usually about the third week of April, other cool season crops can be planted. These include beets, broccoli, cabbage, carrots, cauliflower, celery, chard, kohlrabi, parsnips, early potatoes, and turnips. Broccoli, cabbage, and cauliflower are typically set out in the garden as transplants and not started from seed.


Some vegetable crops are more successful when started from seed indoors, giving them a head start on the season. The crops that do best planted out in the garden as transplants are tomato, hot pepper, sweet pepper, and eggplant. Other crops do better when directly seeded in the garden. This includes beans, corn, carrots, radishes, and onions.

Melons, cukes, and squash are so easy to plant from seed, that it’s best to directly seed them in the garden, but some long season varieties may benefit from that little head start that transplants provide. However, melon, watermelon, squash, and cucumber transplants should be relatively young and small with only about two true adult leaves when placed in the garden. Larger transplants in small pots will suffer from root damage and stress when transplanted in the garden, losing any potential advantage.


Planting from seed is easy, but care should be taken to plant it at the correct depth. When planted too deep, seed may not come up. Usually the seed packet will tell you the correct depth but here’s a good rule of thumb: small seeds (lettuce, radishes, carrots, cabbage) are planted one-half inch deep, medium sized seeds (beets) three-quarters inch deep, and large seeds (beans, squash, corn) one inch deep.


Often gardeners will pre-soak the seed of certain slow-germinating vegetables to encourage quicker sprouting in the garden. Seeds typically pre-soaked for 24 hours before planting include beets, peas, and spinach. Some gardeners also soak bean, corn, and squash seed, but this isn’t usually necessary if you keep the garden soil moist after planting.

Published: 4/23/2011 10:37 AM


written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

The “ideal” soil for vegetable gardening is one that is slightly acid, well-drained, and fertile. The ideal soil has sufficient levels of decayed organic matter is also deep, loose, and free of weeds and disease organisms.

Unfortunately for us gardeners, the “ideal” garden soil is just that, an ideal. Good garden soil is developed over time. There are no magic additives and no quick fixes that will instantly change regular or bad soil into the perfect garden soil. However, even less than perfect soils can be coaxed into growing productive gardens.

First, I would recommend getting a soil test done at one of the local soil testing labs. A soil test gives you a starting point regarding soil fertility, pH, and organic matter content. Based on past experience, I predict your soil will be slightly to moderately alkaline. This is typical for local home garden soils. One home garden soil test that I recently reviewed revealed a pH of 8.2 and another had a pH of 7.9. Both soils were within a range where most vegetables will grow without any problem.

Your soil will also most likely be low (less than 1 per cent) in organic matter and lacking nitrogen. Depending on the soil type and past fertilizing practices in the area, the soil may or may not be lacking phosphorus or potassium. Knowing your current nutrient levels will help you avoid adding unnecessary fertilizer and avert a buildup of excessive amounts of these nutrients.

While there is no magic additive, your best path to building a good garden soil is the addition of organic matter. In sandy soils organic matter helps improve water and nutrient retention. In heavier soils, organic matter aids in aeration and drainage.

Organic matter may sound like that magic additive that I mentioned earlier, but the improvement process is gradual. Only about two to three inches of organic matter should be added to the soil each year and mixed in with the soil to a depth of six to eight inches. Mulching with organic matter during the summer is also a great way to help add organic matter to the soil.

So what qualifies as organic matter. There are a variety of plant-derived materials that qualify as “organic matter,” such as compost, grass clippings, chopped leaves, coconut coir, and peat moss.

It’s not advisable to add woody materials, such as sawdust or wood chips, conifer needles, animal bedding, or straw to your garden soil as sources of organic matter because they’re considered high in carbon and low in nitrogen. It takes a long time for them to decay. Soil microorganisms responsible for breaking down organic matter can use up all the available nitrogen in the soil when “eating” high carbon materials. With no available nitrogen, your garden plants will have a hard time growing without extra applications of nitrogen fertilizer. Also, caution should be taken when using grass clippings if pesticides have been used on the lawn. Manures can cause problems because they often contain weed seeds.

My recommendation is to use quality compost that you make yourself or purchase from a local nursery supplier. Add organic matter to your garden soil every year and you’ll build a better soil.

Published: 4/16/2011 10:26 AM


written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

Early each spring I get calls about a variety of creepy and crawly creatures that show up in yards, gardens, and sometimes even in garages or houses. The most commonly encountered creatures are dark grey to black “worms” that appear in large numbers along sidewalks and in landscape beds. Most people don’t want to get up close and personal enough to describe these worms, so all they can tell me is that they curl up when touched or dead.

Although I have a good idea of this “worm’s” identification, I usually ask folks to bring me a sample because it’s very difficult to accurately identify insects and their relatives over the phone. Invariably, the “worms” turn out to be millepedes. Millepedes are not insects or worms, but are considered wormlike arthropods. Their elongated body is roundish and segmented with each segment, except for the front ones, having two pairs of legs. With four legs per segment it’s no wonder that they were named millepedes which means “a thousand legs”… although they fall far short of actually having that many legs.

There are different species of millepedes found in the garden, some are small ones only measuring a few millimeters in length and others grow to an inch or more long. Typically, the ones found in area gardens are brownish to dark grey and one half to three quarters of an inch long. As arthropods, their hard exoskeleton makes them “crunchy” instead of squishy when crushed.

With so many legs you would think that millepedes would be fast moving, but they’re not. They don’t need to be fast since their food isn’t hard to catch. Millepedes are “recyclers” feeding on decaying organic matter. They’re usually found where there is some type of moist decaying plant refuse… in compost, leaf piles, thatch, manure, and soils high in organic matter.

Most of the year, you may encounter one or two millepedes here or there in the garden, but in the spring and sometimes in early fall massive numbers emerge prompting calls to me asking what to do about all these “worms.”

When a sizable group of millepedes emerge in the spring or fall, experts tell us that there are several possible causes. They say that the most likely cause is population pressure, where their numbers have built up to high enough levels that they’re competing for food and habitat, prompting an exodus to find a new place to live.

The experts also note that there may be other reasons for the appearance of massive numbers of millepedes. If their habitat is destroyed or abruptly changed in some way, they will move. Warm spring weather may dry up their habitat and because they need moist conditions to live, the millepedes will suddenly move elsewhere. While they do require moisture, excessive moisture or standing water is a also a problem that requires a change of address. Even spring garden cleanup, can result in the destruction of millepede habitat.

When you encounter these many-legged recycling arthropods, you need not be concerned. They should be considered beneficial in the garden and are only a nuisance when suddenly present in large numbers. If masses of millepedes appear, the best solution is to sweep them up or use a shop-vac for cleanup. If you’re bothered by mass migrations of millepedes once or more a year, consider eliminating places around your home where they have food and moisture.

Published: 4/9/2011 10:16 AM


written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

Arborvitae is unarguably the shrub most commonly used to create an evergreen hedge, here and around the country. Gardeners who are tired of seeing arborvitae used over and over again for hedges, often ask me for a comparable substitute. There isn’t one. Arborvitae are the mainstay of evergreen hedges because they’re perfect for creating a “green” fence or boundary.

Arborvitae are a dense evergreen shrub with a long life. They have no serious insect pest problems in our area, as well as no common leaf diseases or blights. They’re tolerant of our local alkaline soils and don’t have any difficulty enduring our scorching summer or cold winter conditions. Their one drawback is that they’re subject to root rot if planted too deep or in poorly drained sites. Root rot can also be a serious problem if over-watered.

As a testament to their longevity, a drive around older areas of the Tri-Cities reveals how well arborvitae do in our area. However, you also might note just how big arborvitae can get. The species form of the eastern arborvitae (Thuja occidentalis), also known as the American arborvitae, can grow to a height of 60 feet and a spread of 10 to 15 feet.

Sixty feet is tall! No wonder people feel a need to chop them back when they get “too tall.” When those big old arborvitae were originally planted more than twenty or thirty years ago, there probably wasn’t much of a choice of cultivars. Many planted the species form to create hedges. Today, nurseries sell a variety of different arborvitae cultivars with different mature sizes, shapes, and even foliage colors. If you’re considering planting an arborvitae hedge, check out the different cultivars available from your local nursery or nursery catalogs.

Here are just a few of the popular ones:

Pyrimidalis – Smaller than the species, this cultivar still reaches a fairly lofty height, growing 20-30 feet tall and 5feet wide. Without shearing, it has a formal outline with bright green leaves that turn bronzy in the fall and winter.

Emerald Green (aka Smaragd) – Introduced in 1950, this cultivar has been around for a while. It has a narrow pyramidal form and grows to a height of 10-15 feet and a width of 5 feet, making it much smaller than the species. It has both good hardiness and heat tolerance.

Degroot’s Spire – This cultivar is a narrow columnar form growing 10-12 feet tall and 3-5 feet wide. The branchlets are spirally arranged giving the plant a natural spiral form. Foliage turns bronzy-purple during the winter.

Holmstrup – Holmstrup has also been around since the 1950s. It’s has a compact, slow growing conical form with a narrow, pyramidal shape growing to 5-10 feet tall and 2 feet wide. It stays dark green all year and is very hardy. (‘Miky’ is a cute little sport of ‘Holmstrup’ that’s shorter and even more compact.)

Techny – This slow growing arborvitae has a broad-based pyramidal form and grows to 10-15 feet tall and 6-8 feet wide at the base. It has dense, dark green leaves all year.

So if you’re considering planting an evergreen hedge, look for an arborvitae cultivar that’s the size and shape you need so you won’t be enslaved with regular shearing of your hedge. I’ve just listed some of the popular cultivars. Check with your local nursery to find out what different ones they have available.

Published: 4/2/2011 10:01 AM


written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

We’re all anxious to get “growing.” One gardener told me he had already planted his tomato seeds and they were starting to spout. It’s a bit too early for seed planting, but now is the time to be planning your garden and ordering seed. If you have n’t started yet, you should. It’s still winter, but spring will be here before we know it… I hope.

Part of the fun of gardening is trying something new or different every year. I like to check out the new vegetable and flower varieties that the seed companies are introducing.

Johnny’s Selected Seeds ( is offering a new eggplant called ‘Barbarella.’ This new variety has beautiful, rounded 4 to 6 inch diameter purple fruit that are both tender and tasty. Each upright plant bears 5 to 6 fruit. If you’re a gardener who’s trying to incorporate edibles into your landscape, the pretty purple fruit of this plant will contrast well with yellow marigolds.

Traditionally when you grow potatoes in the garden you start with “seed potatoes.” These are cut up pieces of potato that have one or more “eyes” or buds from which new plants sprout and grow. Seed potatoes are easy to plant, but when spring weather is cold and damp they may rot before sprouting. A way around this is to use already sprouted plants. Grimes Wholesale is selling sprouted “Quick Sprout” plants to growers who pot them in 4 inch pots for sale at garden centers. This will give gardeners a fast start to their potato season.

Look for ‘Quick Sprout’ plants at the garden store or consider growing your potatoes from seed pieces that can be ordered from a company almost within “hollering” distance from here. Irish Eyes Garden Seeds ( is located just outside of Ellensburg, WA. They specialize in potatoes, garlic, vegetable, and flower seed with a focus on organic seed and heirloom varieties.

Heirloom vegetable varieties, especially tomato varieties, have become increasingly popular in the last five years. ‘Brandywine’ has been voted one of the top best tasting varieties in taste tests around the country. However, area gardeners often don’t have much luck with Brandywine because it’s very late to mature and the deeply lobed fruit often split before maturity. Brandywine failures have driven many gardeners back to more reliable modern hybrids. New to the market are hybrids of the classic Brandywine tomato. ‘Pink Brandymaster’ and ‘Red Brandymaster’ are F1 hybrids that produce medium to large firm fruit with the prized Brandywine flavor. The plants have potato-shaped leaves on indeterminate vines. You can get Brandymaster seed from Totally Tomatoes (

Another new wonder of the plant breeding world is a seedless tomato, ‘Sweet Seedless’. This variety will be great for people who can’t eat seeds because of an intestinal disorder. Available from W. Atlee Burpee and Co ( the fruit have a good, sweet flavor and the vines are indeterminate.

Published: 2/19/2011 3:40 PM


written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

Gardeners with spring fever are getting out in their yards more… when the days are warmer and sunnier. Many are noting with dismay brown or dead foliage on their needled and broadleaf evergreens. Some assume that it’s the affect of the severely cold temperatures we had in early winter. Others aren’t sure and are bringing in samples for me to check for signs of life.

Most of the evergreens with brown or bleached needles or leaves are suffering from a problem called winter burn. It’s called “winter burn” because it looks like the foliage was scorched by fire. Winter burn would be more correctly named “winter drying damage.” Winter burn happens when wind and sun cause increased water loss from the leaves. If the soil is frozen from cold temperatures, the water in the leaves can’t be replaced and dehydrated leaf tissues die and turn brown.

Winter burn tends to be worse on the side or sides of an evergreen exposed to sun and wind. These conditions increase water loss through the leaves and lead to more severe winter burn.

Winter burn will also be worse on plants that were drought stressed going into winter or if the soil was dry in early winter before the soil froze. It’s important to remember to water evergreens in fall and winter months when the soil isn’t frozen and the weather is relatively mild. Evergreens are susceptible to drought stress at these times because they’re still losing moisture through their needles and leaves even though they appear dormant.

Evergreen trees and shrubs planted in mid to late fall are particularly vulnerable to winter burn because they experience stress from root injury that occurs during the planting process. In addition, if the weather turns cold soon after planting, they don’t have enough time to replace damaged roots and are unable to absorb enough moisture from the soil. It’s especially important that the soil in the root zone of recently planted evergreens be kept adequately moist throughout mild fall and winter weather.

Our region has been coddled by relatively mild winters for a number of years in succession. Perhaps a perceived regional climate change has lulled us into thinking that winter burn and winter damage from cold temperatures were a thing of the past , but periods of severe cold this winter have resulted in winter burn on many local pines, arborvitae, Chamaecyparis, boxwood, euonymus, rhododendron, and other evergreens.

What can we do? Some of the plants I’ve looked at appear to have healthy buds and new growth will develop normally when spring arrives. The damage promises to be more severe on others, like boxwood, where entire twigs and branches may be dead. Sit tight and be patient. See if new growth begins to grow with the arrival of spring. When it does, prune out all dead growth.

Published: 2/26/2011 3:24 PM


written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

“The main purpose of spring lawn care is to get the grass through the summer. ” That’s a quote from David Robson, an Extension Horticulturist at the University of Illinois. He’s absolutely right. Spring lawn care should not be aimed at being the first person on the street to have rapidly growing green grass. Your goal should be to have a healthy lawn all season long.

According to Robson, “Early spring fertilizer applications should be avoided, if possible.” Lawn owners are often tempted to fertilize their lawn in early spring because they’re rewarded with rapid green growth. However, this early top growth is at the expense of the unseen roots that are regenerating after their partial dieback over the winter. In late winter and early spring the roots begin to grow back, favored by mild spring weather. Fertilizer stimulates top growth that uses up energy reserves needed to develop a deep, dense root system.

After a couple of bouts of severely cold winter weather, our area lawns definitely look peaked. No doubt your first impulse will be to fertilize. Wait. It will be hard, but don’t fertilize until the first of May… no matter how great the temptation.

Another temptation is to start watering the lawn regularly as soon as irrigation water becomes available. Wait. Dig down several inches in your soil and see if it’s dry. Water only if needed. You will encourage a deeper root system by watering deeply and as infrequently as possible. Watering daily should be avoided during the cooler weather of spring and early summer. If you have a timer on your sprinkler system, adjust it regularly as the weather changes.

One thing you should do in early spring is start mowing as soon your grass starts growing. Most area lawns are composed primarily of bluegrass and are best mowed at heights of 2 to 2.5 inches. Mow the grass whenever it reaches a height of 3 to 4 inches. Don’t forget to keep your mower blade sharp as it makes a cleaner cut which is better for the grass and leaves a more manicured look.

If thatch is a problem in your lawn, early spring is a good time to rent a power rake and remove it. A thatch “problem” is a thatch layer that’s greater than .5 inch thick. Thick thatch hampers the movement of water, air, and fertilizer into the root zone. In hot weather thick thatch has a tendency to dry out and resist rewetting, causing large areas of lawn to turn brown and die.

If your thatch is too thick, greater than one inch, you’ll need to make several passes in different directions across the entire lawn, lowering the machine’s height each time. In severe situations, power raking may leave areas of your lawn bare and over-seeding will be necessary.

If you have thin areas of lawn that require over-seeding or you’re starting a new lawn from seed, April and May are great times for sowing grass seed. However, make sure you don’t apply a “crabgrass preventer” herbicide product too, as it will also prevent your grass seed from sprouting.

Remember the goal isn’t to have a green lawn next week, the goal is to have a green lawn all summer long. It’s only early spring, but giving your lawn the right care at the right times will help it get through punishing summer weather looking great.

Published: 3/26/2011 3:12 PM


written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

I’ve been receiving numerous inquiries from local gardeners about how to control the moss that’s invading their lawns and gardens. Most of us know that “a rolling stone gathers no moss,” but that’s all we know about this primitive green plant.

Moss reproduces by spores instead of seeds. Botanists consider moss to be lacking true roots, stems, or flowers. They’re an opportunistic plant that can be found growing in all parts of the world in diverse environments where there’s plenty of moisture available during at least part of the year. Mosses can be found growing in or on rocks, roofs, concrete, forest floors, local lawns, as well as at the bottom of lakes, ponds, and streams.

Because mosses lack true roots and vascular tissues, one might wonder how they get needed water and nutrients. Some types have rhizoids which are root-like filaments that act as roots. Others types of moss absorb nutrients from free water on their leaves. Most mosses require very little, if any, soil to grow.

In the Pacific Northwest, it’s not unusual to find moss growing in woodland areas and plaguing structures, lawns and gardens west of the Cascades. It is surprising that moss can be a problem in our dry shrub-steppe area of central Washington. During the cool, moist periods of the year, moss thrives and grows and then becomes dormant during the hot, dry times of the year. We have just experienced a cool, “wet” fall, winter, and early spring during which moss has apparently prospered.

Moss is opportunistic, not aggressive. Whenever moss becomes a problem in gardens or a lawn, gardeners should investigate why it’s growing there. Moss tends to grow where the soil is very compacted, the drainage is poor, the soil stays very wet for periods of time, where it’s shaded, or where the fertility is poor… or a combination of these conditions. Acid soils also favor moss growth, but that’s usually not a problem in our region.

In lawns, you can rake or power rake to remove the moss. There are also chemicals that can be applied to kill moss and not harm the grass. However, the real key to control is promoting healthy vigorous turf with proper watering, adequate fertilization, and both good aeration and drainage. Dense shade leads to thinning of lawn grass and also favors moss growth. If the shade is from trees and shrubs, consider having them thinned to allow more light or tolerate the moss.

In gardens, there are no chemicals for control of moss that won’t harm other plants. Your best option in flower, vegetable, and landscape beds is to scrape the moss off the soil surface using a hoe. Without real roots, it’s only growing on the surface and is easy to remove. Correct any drainage or compaction problems.

Moss is not harmful to your lawn or garden, but it does indicate that there may be a drainage or soil compaction problem. If these conditions don’t seem to be hampering the growth of your garden plants, you might even consider yourself lucky. One current gardening trend is moss gardening. There’s even a place on-line ( where you can buy moss. I guess one gardener’s “trash” is another’s treasure.

In addition to mosses, area gardeners are sometimes bothered by a different low growing primitive plant closely related to moss called liverwort. Liverwort has a branching flat and wavy ribbon-like body that grows along the soil and is favored by the same conditions that favor moss and is controlled in the same manner as moss.

Published: 3/19/2011 3:05 PM


written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

You know the feeling? The one that you feel deep in the pit of your stomach when you go by a homeless person asking for food. That’s exactly how Alaskan garden columnist Jeff Lowenfels felt after such an encounter when visiting Washington, D.C. over 15 years ago. A person on the street asked Jeff for help because he was hungry. Warned about panhandlers, Jeff didn’t give him any money, but he didn’t like the guilt that followed him home.

When he returned to Anchorage, he decided to do something about the problem. He asked his readers to “Plant-a-Row” of vegetables for the local soup kitchen. The concept was easy… get his gardening readers to plant some extra vegetables to share with those who were hungry and needed help. This idea worked so well in Anchorage that Jeff shared it with other garden writers in the Garden Writers Association (GWA). GWA adopted the “Plant a Row” program in 1995.

The need now is even greater than it was in 1995. Requests for assistance from food banks has increased by 70 per cent in recent years, with adults and children often turned away because of a lack of food. The U.S. Department of Agriculture indicates that one of eight households in the U.S. are at risk with many skipping meals or going without food for an entire day.

The Plant-a-Row (PAR) program is so simple. If you’re planting in raised beds and not in rows, just plant a little extra and donate that extra produce to one of our local food banks. Even if you don’t plant an extra row, chances are you’ll have some extra zucchini, carrots, tomatoes, or other produce that you can donate. Our local food banks and soup kitchens welcome fresh, good quality veggies and fruit for their clients.

Imagine if every gardener in this country plants just a little extra in their garden, what an impact we could make on hunger in this country. Since the PAR program started in 1995, over 14 million pounds of produce have been donated by gardeners. That’s the equivalent of 50 million meals. No tax money or government funds have been needed to achieve this. It’s all been because of the hard work and warm hearts of gardeners like you!

You can help by donating garden-grown produce or you can get more actively involved with one of the many local school and community garden projects that are sprouting up. This meeting is being coordinated by Second Harvest to discuss some of the major problems encountered when developing a school or community garden. This first conversation is an excellent opportunity for stakeholders and interested community members to come together and talk about the exciting potential school and community gardens. Another topic of discussion will be the Plant-a-Row program and coordinating the collection of produce for our local food banks.

WSU Extension Master Gardeners from around the state support the PAR program, donating produce from demonstration gardens and providing gardening advice to local gardeners. In fact, did you know that our local Benton-Franklin WSU Master Gardeners donate the produce from their vegetable garden in the Demonstration Garden in Kennewick to local food banks?

Published: 3/12/2011 2:58 PM


written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

It’s the “Year of the Rabbit” for the Chinese, but it’s also the “Year of the Zinnia” for U.S. gardeners. Each year the National Garden Bureau, representing the professional horticulture industry, selects one flower to be showcased. Plants selected for this honor are chosen because they’re popular, easy-to-grow for gardeners, widely adaptable, and versatile.

The zinnia, this year’s honoree, is an old garden favorite. The ancestor of the modern zinnia is Zinnia elegans, native to Mexico. As a native species, Zinnia elegans didn’t look attractive to the Spanish colonials who “discovered” this small plant with purple-red daisy-like flowers. Ugly or not, zinnias were taken to Europe where they received their scientific name in the 1700

s from Dr. Johann Gottfried Zinn, the first botanist to write about them.

Probably because native zinnias were not particularly attractive plants, breeders didn’t pay much attention to them for about 100 years. The result of their initial efforts was a double-flowered plant that was still not pretty enough to create excitement in the gardening world. In 1920, additional efforts by breeders yielded two fairly attractive varieties with dahlia-like flowers, ‘Giant Dahlia’ and ‘California Giant.’

Over the years, continued breeding efforts have yielded common zinnias in different sizes, from eight inches to over three feet in height, and in a variety of brightly colored flower forms. Zinnia flower colors include yellow, gold, pink, rose, red, orange, salmon, purple, ivory and white. The cheery flowers of the common zinnia (Zinnia elegans) will keep coming through the summer only if their faded flowers are removed regularly. This practice is called deadheading.

While the common zinnia proved a dependable garden flower in our grandmothers’ gardens, today’s gardeners often find the required deadheading and tendency to develop mildew too much trouble. For more modern zinnias, plant breeders have looked to another native Mexican zinnia, Zinnia angustifolia, for help. Breeding efforts have combined the best traits of these two species and have yielded more compact zinnias that don’t require deadheading to keep them flowering. These new hybrids are also resistant to powdery mildew and are more tolerant of heat and humidity.

My current zinnia favorites are in the Profusion series of zinnias. Introduced in 1994, ‘Profusion Orange’ was the first in the series with orange flowers. White, cherry, apricot, gold, and scarlet-orange flowered members of the series followed. Profusion zinnias have two-inch single and double flowers. Their compact branched plants grow from 12 to 18 inches tall and 24 inches wide. They keep flowering through fall and don’t require deadheading.

I hope to try some of the Zahara series of zinnias this year. Zahara zinnias are also hybrids of the Z. elegans and Z. angustifolia. This newest series touts flowers that are 20 per cent larger than the Profusion series. Zahara flower colors include coral rose, orange-red, scarlet, white, yellow, double cherry, double orange-red and a delightful white and pink bi-color called Starlight Rose.

Zahara zinnias are heat loving plants that thrive under hot, sunny conditions. Once established, they’re drought tolerant. Their bushy plants produce flowers all season long and grow to a height and width of 12 to 18 inches with double-flowered varieties growing 16 to 20 inches in size. Both the Zahara and Profusion zinnias are great in containers and flower beds.

The WSU Extension Master Gardeners will be planting some of the Zahara zinnias in the Formal Garden in The Master Gardener Demonstration Garden this year. Drop by during the summer to see these tough but pretty new zinnias.

Published: 3/5/2011 2:51 PM



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