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Garden Tips

Archive for October 2014

REFRESHING YOUR CONTAINER GARDEN POTTING MIX

written by
Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA
published- MAY 9, 2014

REFRESHING YOUR CONTAINER GARDEN POTTING MIX

I grow all my annual flowers in big pots on my back patio. At last count, there were ten of them and replacing the potting mix in them every year would bankrupt me. Instead of buying new potting mix each spring, I “refresh” and reuse the old.

I start by digging out all the dead roots and stems of last year’s plants, if I didn’t remove them in the fall. Potting mixes tends to compact over the course of the growing season, so next I use a trowel and garden knife to break apart residual roots and loosen the mix to a depth of at least eight inches. Along with loosening the mix each spring, I also add some controlled-release fertilizer and work it into those top eight inches.

After refreshing the mix, I add some new potting mix if the level in the pot has declined due to decomposition or from removing the old plant roots intermingled with mix. After several years, I may replace the old mix in the top half of the pot with new because it is not draining well due to the break down of organic matter over time. When I remove old mix, I don’t throw it away. Instead, I mix it into my sandy garden soil.

I recommend investing in a quality potting mix when starting a new container. I prefer a mix that consists of peat moss or coconut coir, perlite or pumice, earthworm castings, and some compost. I also like the ones that contain controlled-release fertilizer that the label indicates will last for several months.

I mentioned earlier adding fertilizer to potting mix that is being reused. This is necessary because last year’s plants probably used up most of the available nutrients and whatever they did not use was likely lost through leaching with the frequent watering necessitated by hot weather. The addition of fertilizer to reused potting mix is important for the good growth of the annuals, flower or vegetables, planted in containers. Just imagine the fertilizer needs of a vigorous growing sweet potato vine, trailing petunia, or tomato vine!

I prefer controlled-release or “time-release” fertilizers for use in my containers. They are more expensive than traditional water soluble granular fertilizers, but I like the convenience of not needing to reapply them frequently during the season. When I select a controlled-release fertilizer, I look for one that is a balanced fertilizer, one that contains nitrogen (N), phosphorus (P), and potassium (K). The percentage of these by total weight is indicated somewhere on the product label in that order: N, P, and K. Because the amount of nutrients vary with different types and brands of fertilizer, I follow the recommendation on the label for the amount to apply to a particular size pot.

Product labels also indicate the length of time that the nutrients should last. However, because hot summer and early fall weather in our region dictates frequent watering, it may not last that long. You should consider applying the same fertilizer again in mid-summer. If not, you can use a water soluble liquid or crystallized fertilizer to add some nutrients later in the season if the plants are showing signs of nutrient deficiency, such as yellowing leaves or poor growth.

Anxious to get started, I readied by containers over a month ago. Now I am anxiously waiting for consistently warm and calmer weather before I get started. Maybe this weekend? We’ll see.

Published: 5/9/2014 11:43 AM

GROWING ORCHIDS IS EASY

written by
Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA
published- MAY 2, 2014

GROWING ORCHIDS IS EASY

Several weeks ago I was in a big box store and noticed that the gorgeous orchids for sale were flying off the shelves while the traditional pretty potted Easter lilies were just sitting there. I suspect that many of these orchids were destined to be gifts for someone special.

The owners of gifted orchids are often orchid novices. They are faced with the dilemma of what to do with a beautiful orchid after it stops flowering. Orchids have the reputation of being hot house plants that need to be pampered. In fact, many types of orchids are easy to grow and novice owners can save their gifts from an untimely demise with just a little knowledge.

While some orchids are fussy about temperature and light, the ones typically sold in big box and grocery stores are Phalaenopsis orchids. Phalaenopsis orchids, also known as moth orchids, are considered low light orchids and can be grown easily in the home. However, “low” light is a relative term. They still need a good amount of light and will do best in an east facing window. You can also situate them in a southern or western facing window, but they will need the protection of a sheer curtain to block them from direct sunlight.

The Phalaenopsis orchids do not need the warm temperatures of a greenhouse. The temperatures that keep us happy indoors will keep them happy too.

When it comes to potting mix and watering, Phalaenopsis orchids, as well as other orchids, are a bit finicky. Orchid growers each have their preferred mixes. Generally the mixes should drain quickly but also retain some water for good root growth. Orchid potting mix ingredients may include fir bark, tree fern, sphagnum moss, perlite, lava rock and other materials that meet the criteria.

Many of the mass market Phalaenopsis orchids come planted in potting mixes that consist mostly of fir bark. It fits the requirements of being fast draining while holding some moisture, but bark-based mixes tend to break down with time. As fir bark gradually decomposes, it becomes a finer and finer texture.

The broken down bark holds more moisture and nutrients, but also does not allow the roots to get as much air as needed. That is when you need to repot. Local orchid experts tell me that most orchids planted in fir bark will need to be repotted at least every two years. If you don’t, the roots will start to rot and the plant will decline and die.

I have six miniature orchids sitting on the sill of my east facing kitchen window. Because orchids like some humidity, I have them sitting on a bed of moist pebbles in window-box trays. Occasionally one of my orchids bloom, providing me with a great reward in return for very little effort. I even have a tiny orchid that I received last September and it is still blooming! Growing orchids is easy.

Published: 5/2/2014 11:44 AM

WHAT’S WRONG WITH MY CUCURBIT?

written by
Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA
published- JUNE 27, 2014

WHAT’S WRONG WITH MY CUCURBIT?

Cucurbits (squash, cukes, and melons) are popular garden veggies. That is probably why questions about cucurbits are second only to tomatoes when it comes to problems that gardeners encounter in their vegetable gardens.

A common question is, ‘why aren’t I getting any squash even though my plants have a lot of flowers?’ To understand the answer it is important to know that cucurbits have separate male and female flowers. Only the female flowers can produce fruit and only the males produce the pollen needed for pollination and fruit development. The cucurbits depend primarily on honeybees to transfer the pollen from the male flowers to the females.

In order for pollination to occur, both male and female flowers must be open at the same time. Typically, cucurbits produce all male flowers at the start of flowering and a little later also produce female flowers. Conversely, plants of hybrid cucurbits generally produce female flowers first and male flowers second. However, before long both sexes of flowers are open at the same time and then the bees must go to work.

Once male and female flowers are blooming at the same time, there are several reasons that fruit still may not develop. Lack of honeybees or low bee activity due to hot weather, wind, or rain can hamper successful pollination.

If the honeybee population is low or nonexistent, you can assume the duties of a honeybee. Do this by picking a freshly open male flower (they have pollen in the center) and removing the petals, leaving the center portion (anthers) with the pollen. Insert this into the center of a newly open female flower (has a baby fruit at its base). Gently move the anthers around to transfer the pollen from the anthers to the center structure (stigma) in the female flower.

Another common cucurbit question comes from area gardeners when they discover small to large dry whitish or tan spots on the leaves of squash, melons, or cukes. It is typically most severe on the plant’s larger, older leaves and not evident on the youngest leaves. It looks like a disease problem, but it usually is wind injury. This occurs when the winds buffets the leaves about, causing the spiny surfaces of the leaves and stems to wound themselves. Badly injured leaves will be very brittle and often tear after additional windy weather. Placing a garden in a less exposed spot or shielding the plants from wind in some way might help.

Area gardeners also wonder why the leaves of squash wilt during the day and then perk back up in the evening. Is it a wilt disease or squash bugs? No, this daytime wilting indicates that the leaves are not being supplied with enough water to keep up with the amount of water they are losing through their leaves during the heat of the day. This ‘lack’ of water may be caused by too little soil moisture, a poorly developed root system, root rot from too much water or poor drainage, or root damage from enthusiastic weed cultivation. Consider the situation and try to remedy it for a healthier, more productive plant that does not wilt during the day.

Other common problems to look for on cucurbits are squash bugs and powdery mildew. You can find out more about these on the WSU website called ‘Hortsense,’ short for Horticultural Sense. You can find Hortsense at http://pep.wsu.edu/hortsense/. Start looking for squash bugs now.

Published: 6/27/2014 11:40 AM

CONSERVE IRRIGATION WATER BY NOT WASTING IT

written by
Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA
published- JUNE 20, 2014

CONSERVE IRRIGATION WATER BY NOT WASTING IT

It is estimated that over 50 percent of the water used by an average household is used for irrigating our lawns, landscape and garden. Luckily for us, we have enough water for irrigation this year. It looked like we might have to tighten our belts in regards to watering when the snowpack was well below normal in early winter. Fortunately, late winter snows in the Cascades saved us, but climatologists predict that our good fortune is not likely to last.

It is time to start learning and practicing water conservation now, so we will be prepared for any water shortages looming in the future. One way to conserve water is simply not to waste it. How often do you see irrigation water running down the street at this time of year? There are easy ways to avoid this wasteful runoff.

One way is to slow down. Often water is being applied faster than it can sink into the soil, especially on sloped areas. A simple solution is to apply the water more slowly in several short runs with a short break in between each application until a total of 1 to 1.5 inches of water is applied. This gives the water a chance to percolate down into the soil instead of running off.

Water only when needed. Often area residents rely on timers to turn water on and off based on a set daily schedule, never adjusting for weather or checking soil moisture to see if the lawn or plants actually need water. This ‘set it and forget it’ practice is easy, but wasteful. Plus, it does not encourage deep root systems or healthy plants.

Dr. Troy Peters, WSU Extension Irrigation Specialist, notes that your lawn and garden do not need the same amount of water in the spring and fall as they do in the hot part of the summer. For example, he indicates lawns in Yakima, WA ‘only use about .25 inch of water per week in April and October, 1.25 inches per week in May and September, 1.6 inches per week in June and August, and a little over 2 inches per week in July.’

If leave your controller programmed on a setting of 15 minutes every day for the entire season it probably means that you are applying too much water in the spring and fall and too little water in the middle of summer. Peters recommends resetting your timer at least once a month to adjust for the changing irrigation needs.

If your soil is a silt-loam, Peters also recommends putting all the water needed during the week on in one weekly irrigation, not just a little bit every day. Peters points out that ‘soil can only hold so much water.’ When you put on more water than the soil can hold, the excess water is wasted. During the summer when more than an inch of water per week is needed, Peters suggests splitting the total and applying half of the water with two separate runs per week if the soil is a silt loam. However, on sandy soils, you will have to irrigate more often, but should try not to irrigate every day if possible.

There are other ways to conserve lawn and garden irrigation water, but trying not to waste it is a good start.

Published: 6/20/2014 11:41 AM

GARDEN PROBLEMS BECOME OPPORTUNITIES

written by
Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA
published- JUNE 13, 2014

GARDEN PROBLEMS BECOME OPPORTUNITIES

I recently took a watercolor class and our instructor, Chris Blevins, taught us that we should view a mistake as an opportunity to take a painting in a different direction. She calls these Aswap-portunities.@ The same goes for gardeners when a landscape plant dies, grows too big for its location, or just does not perform up to expectations. These problems should be looked at as opportunities to do something different.

For example, I had several scraggly aging lavender plants that were crowding my Stella d=Oro dayliliies in my front landscape. They were no longer attractive and I was tired of deadheading them when they were done flowering. I dug them out this spring, giving me space to plant a small landscape rose that will require less attention. My choice was >Oso Easy Cherry Pie.= It has bright roses flowers and shiny green leaves. It needs little pruning, no deadheading, and does not need spraying.

At the other end of the same bed I have Oso Happy Smoothie, another in Proven Winner=s Oso landscape rose series. It is pretty much a perfect rose for the landscape and it is thornless. From late spring to frost it produces hot pink single flowers with white centers. Deadheading and spraying are also not necessary.

I also decided two shrubs in my back yard needed to go. One of these was the >Bloomerang Purple Lilac= that I was so excited about when it first became available. Except for the flowers it was not and attractive plant. I also removed a >Silver Anniversary= abelia that grew well but looked ragged most of the time. Now I have a couple of spots where I can try something new, which is always exciting for a gardener.

My other Aopportunities@ have come from a few flowering perennials that didn’t make it through the winter. I am still looking for the perfect replacements.

Two shrubs that are staying put are also Proven Winner introductions. They are Lo & Behold >Ice Chip= with white flowers and silvery leaves and >Lilac Chip= with lavender-pink blooms and green leaves. They are darling little butterfly bushes that fit right into a shrub or perennial bed. Both >Ice Chip= and >Lilac Chip= have a mounded growth habit growing about two feet tall and two to three feet wide, diminutive compared to many other butterfly bushes.

Both AChips@ have sterile flowers so they are not invasive and deadheading is not needed. These are very carefree shrubs, plus they attract butterflies and hummingbirds. They have no major pest problems and you simply prune them back the back to the ground in late winter.

I am anxious to see what new plant introductions will be available this year and next from plant marketers like Proven Winners, First Editions, Bailey Nurseries, HGTV, and others. I still have a few spots to fill in my landscape and garden. Time to go shopping and take advantage of my Aswap-portunities.@

Published: 6/13/2014 11:42 AM

HERBICIDES CAN CURL LEAVES TOO

written by
Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA
published- JUNE 6, 2014

HERBICIDES CAN CURL LEAVES TOO

This is the time of year that weeds get our attention. As soon as warm weather hits they grow ‘like weeds.’ Then out come a variety of herbicides (weed control chemicals) aimed at killing these unwanted pesky plants in our lawns, landscapes, and gardens. Unfortunately, not using these chemicals properly can injure or kill our desirable plants.

Symptoms of herbicide injury vary depending on the chemical, but common culprits are the growth regulator type herbicides used to kill broadleaf weeds, like dandelions, in lawns. Exposure to the growth regulator herbicides can cause leaf cupping, twisted or distorted growth, and strap-like leaves. The common growth regulator herbicides found in home garden products for lawns are 2,4-D, MCPA, MCPP, and dicamba.

These products are available in liquid form for spray application or in a dry form for applying as a granular. It is very easy to awry when using them in liquid form because wind will cause the spray to drift away from the application ‘target’ area.

To minimize drift, herbicide sprays of any type should only be applied when there is no wind. In our region where it is frequently windy or breezy, this is difficult. The potential for drift can also be reduced by using large spray droplets instead of a fine mist and applying the spray as close to the ground as possible.

The other application choice is a granular herbicide, but desirable plants can still be damaged because of uptake of chemicals through the roots. The labels of products containing dicamba indicate that it should not be used ‘in the root zone of desirable plants.’

If you have trees located in or adjacent to your lawn, it is virtually impossible to avoid applying the chemical in their root zone. The root systems of trees can go out as far as a tree is tall and even further. Garden plants situated next to a treated area could also become damaged via root uptake.

Garden plants can also be exposed to herbicides when grass clippings from recently treated lawns are used as a mulch in the garden. Check product labels for how long you must wait before using the clippings in your garden after application. If you place treated clippings in a compost pile, it is best to compost them for several months before using the compost in the garden.

Other ways to reduce the chance of herbicide injury in the yard and garden include:

1. Avoid applying herbicides in late spring and summer. Herbicides can vaporize during warm (above 80 degrees) weather and float in the air, settling down on plants a long way from the point of application and causing damage. If you plan on using either granular or spray herbicides, do it when the weather is cool in early spring or fall.

2. If you have just a few weeds in the lawn, spot treat them individually or dig them out. A ‘weed popper’ tool works great for this.

3. In landscape beds, apply a three to four inch layer of bark mulch to discourage weeds.

4. In and around the vegetable and flower garden beds use shallow cultivation or simply pull the weeds. I like a stirrup type hoe with an oscillating head. Cultivate frequently to get the weeds when they are small. It is much easier.

I noted last week that the two main causes of curled leaves on garden plants were aphids and herbicide injury. Now we have covered both these culprits.

Published: 6/6/2014 11:43 AM

HOT WEATHER GARDEN WOES

written by
Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA
published- JULY 25, 2014

HOT WEATHER GARDEN WOES

I have lived in this region for over 30 years, but every summer I have a hard time adjusting to our extreme summer heat. This year I had deluded myself into believing that our blissfully mild early summer would continue. Not a chance!

Scorching heat is not only extremely stressful on us, but also on our plants. Some ill affects of the high temperatures on plants are related to cultural factors, such as watering, but the heat itself can lead to a variety of ‘hot weather woes.’ One reason for this is ‘thermoperiod.’

Thermoperiod refers to the daily temperature change from daytime to nighttime.

Plant growth is generally best when daytime temperatures are about 80 degrees and nighttime temperatures are 15 degrees lower, although this varies with the type of plant. With this 15 degree thermoperiod plants are making and building up carbohydrates via photosynthesis at a higher rate than they are being broken down through respiration.

Higher temperatures lead to higher rates of photosynthesis, up to a point. Respiration also increases with higher temperatures. In extremely hot weather carbohydrates are used up more quickly than they can be replaced. As a result growth slows or stops.

That’s why so many garden plants look stressed when 100 degree weather prevails. Even heat tolerant annuals stop growing and flowering. Spent flowers shrivel and no new ones replace them. If they are not drought stressed, they should bounce back just fine with cooler weather.

The failure of plants to produce fruit despite flowering is a common hot weather complaint of veggie gardeners. Many vegetable crops are dependent on cross-pollination by bees. When temperatures go above 100 degrees, bee activity and cross-pollination slows.

Even with plenty of bee activity, pollination and fruit set may still suffer because extremely hot, dry weather reduces the pollen viability of many crops. Blossom-drop or the failure of flowers to set fruit is a frequent complaint in area gardens, even with plants not dependent on insects for pollination. Blistering weather is often the cause for poor fruit set on beans, tomatoes, peppers, squash, cucumbers, and melons. As a result of hot weather these crops may also develop deformed fruit due to incomplete pollination.

If you have trees in your yard, you may also note another hot weather phenomenon, seemingly healthy trees dropping an alarming number of leaves without warning. Some trees will suddenly drop some of their leaves in mid-summer, typically when hot, dry weather arrives. This is a physiologic adjustment because the tree cannot support all the leaves it developed when the weather was cooler and less stressful.

A tree can lose as many as 10% of its leaves without adversely effecting its overall health. However, it is important to make sure the leaf drop is not the result of other stresses such as lack of adequate water, root problems, or an insect infestation. You can help prevent drought stress on shade trees and harmful excessive leaf drop during hot weather by providing them a weekly deep watering.

Our summers are hot. There is no way to escape it, but we can avoid some of these garden woes by selecting plants, including flowers, vegetables, and trees rated as ‘heat tolerant’ and giving them the best growing conditions possible.

GARDEN NOTE: A bee-friendly garden should not only provide a variety of flowering plants that bees like, but also a source of water. An easy way to provide bees with water is with a shallow bird bath, bowl, or plant saucer that contains water and some bee ‘perches,’ such as corks or partially submerged stones.

Published: 7/25/2014 11:38 AM

UGLY LAWNS

written by
Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA
published- JULY 18, 2014

UGLY LAWNS

It’s getting downright ugly out there. I am talking about the brown spots and large areas of lawn turning brown. It is unsightly, but it is not a surprise. There are a variety of possible causes for this blighting of our green grass but watering, other lawn care practices, and weather are at the root of the problem.

Despite the watering wisdom of ‘watering deeply and less frequently,’ most area lawn owners have not opted to follow this sage advice that I offer year after year… after year. I talked a little earlier this season about watering when plants need it, not by relying on a timer that is set at the beginning of the season and never adjusted.

This year we experienced extended cool spring weather. That did not keep the irrigation timers from being set as soon as water was available with the typical 20 minutes per day. Because of the cooler weather, grass remained wet for considerable lengths of time setting up the perfect conditions for damaging lawn fungi to attack.

Pythium may be one of the fungi causing problems. Pythium fungi attack and kill the roots and crown of the grass plants. During cooler weather the disease may start as small yellowish patches that coalesce into larger areas. When it turns warm the disease show up as large areas of wilted and dying turf.

This disease can be avoided with ‘deep, infrequent watering’ and irrigating early in the morning instead of late at night. To reduce spreading the disease, collect and remove grass clippings when you mow. Remove excessive thatch and do not fertilize heavily during warm weather.

Thatch, another topic I have covered numerous times, may also be one of the problems contributing to lawn ugliness. Thatch is an intermingled layer of organic matter that comes from the grass plant itself. It consists of undecomposed grass stem, crown, and root debris. Thatch is not caused by an accumulation of grass clippings as once thought. It results when the grass produces this material faster than it decomposes.

Lawns in our area are predisposed to develop thatch because our soils, especially sandy soils, are generally low in microbial populations responsible for breaking this organic matter down. Plus, most of our area lawns are comprised of Kentucky bluegrass and fine fescue grasses that form more thatch than bunch-type grasses, like turf-type perennial ryegrass.

Many poor lawn care practices encourage the buildup of thatch and discourage microbe populations. Frequent shallow irrigation promotes thatch. Excessive nitrogen fertilization makes grass grow faster and develop thatch at a quicker rate. Infrequent mowing encourages the development of stem tissue and more thatch. Excessive irrigation and compacted soil discourage microbe activity.

The best defense against thatch is good preparation of the soil before seeding or sodding a lawn, followed by sound lawn care practices. This includes deep, infrequent watering; mowing regularly at the recommended height; fertilizing at recommended rates; aerating to relieve soil compaction; and removing thatch when the layer exceeds one-half inch.

Finally, another common cause of large brown spots in lawns during this hot weather is sprinkler coverage. Check how much water is being applied to the brown areas when the sprinklers are on.

Speaking of water, be sure to drink plenty of it when you are gardening outside.

Published: 7/18/2014 11:38 AM

IT ISN’T WHAT YOU THINK IT IS

written by
Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA
published- JULY 11, 2014

IT ISN’T WHAT YOU THINK IT IS

I recently overheard a woman in a local store asking for a spray to kill the little green worms on her lettuce. I had to restrain myself from offering her unsolicited advice. I too had just found ‘little green worms’ on my lettuce, but I recognized them as syrphid fly larvae.

Syrphid flies are also known as hover flies or flower flies because they are usually noticed when hovering over flowers. They may cause alarm because they have a black and yellow striped body, resembling a bee or wasp. However, syrphid flies are benign and do not sting or bite.

The adult flies eat flower pollen and nectar. They are also valuable pollinators. You should not be afraid when you see a syrphid fly hovering around your garden plants, but any aphids present should be very afraid. That is because many types of syrphid flies are predaceous. These syrphid flies lay their eggs near colonies of aphids. The eggs hatch into hungry larvae that will eat hundreds of aphids in a month.

If you see a ‘little green worm’ on a plant infested with aphids, take a close look. Syrphid fly larvae have a tapered body with no legs. They blindly move over the leaf surface searching for aphids to eat. When they find one they use their piercing mouth to suck out its body fluids.

So if you find a little green worm on your lettuce or see a bee-like fly hovering around your flowers, it is likely a sphyrid fly larva or adult. Syrphid flies are beneficial insects that do double duty, eating aphids and helping with pollination. Encourage them instead of buying a spray to kill them.

For much more information about ‘Beneficial Insects, Spiders, and other Mini-Creatures in Your Garden – Who They Are and How to Get Them to Stay’ go to http://cru.cahe.wsu.edu/CEPublications/EM067E/EM067E.pdf for your free downloadable copy of this outstanding and fascinating publication written by Dr. David G. James, Associate Professor, WSU Department of Entomology.

Several local gardeners have come to me recently because they were worried about the silvery patches on the leaves of their zucchini plants. They wondered if it was powdery mildew, a fungus disease that is fairly common in area gardens. It first shows up as small white powdery spots on squash leaves. These spots grow larger until the fungus covers the entire leaf and stem, killing the infected tissues It typically shows up on squash late in the growing season, about the time the plants are finished producing fruit.

Luckily, what these gardeners have encountered is the natural silvery blotchy variegation characteristic of some zucchini cultivars (varieties). It is not a problem and the plants are healthy for now, but it is advisable to watch for signs of powdery mildew on squash, cukes, and melons.

If you have had problems with powdery mildew on your squash before, you may be able to avoid it by doing a few simple things. When possible, plant cultivars that indicate they are resistant to powdery mildew. Don’t plant your squash or other cucurbits where they will be in the shade of other plants or structures for part of the day. Provide good air circulation by not crowding the plants. Finally, rotate your crops so cucurbits are not planted in the same location for at least two years. For more information on powdery mildew go to WSU’s Hortsense Website at: http://pep.wsu.edu/hortsense.

Published: 7/11/2014 11:39 AM

SOIL FOR RAISED BEDS

written by
Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA
published- JULY 4, 2014

SOIL FOR RAISED BEDS

Today’s homeowners have smaller yards and less space for vegetable gardening. Many have opted to use raised beds for growing vegetables as a way to maximize space and minimize garden maintenance.

‘Square-foot’ gardening, popular with some gardeners, is a raised bed system for optimizing garden production promoted by Mel Bartholemew. His system includes using a potting mix that he calls Mel’s Mix. It contains compost, peat moss, and coarse vermiculite. It can be very pricey, especially if you are filling a number of beds.

Gardeners wanting to grow in raised beds do not need to invest in an expensive soil or potting mix. They can use their own soil in low-sided raised beds. Set up the beds and then take the native soil in the pathways around the beds and mix it with some good quality compost (no more than 10 per cent by volume) and place it in the beds.

If there is not enough soil to fill the beds, you will need to bring in soil. True topsoil is natural surface soil scraped up and transported to a site. Topsoil in many regions is more desirable than the subsoil (the soil layer beneath the topsoil) because natural processes have created a crumbly soil structure that is conducive to good plant growth. However, digging and transporting topsoil elsewhere generally destroys this crumbly structure and nullifies its benefits.

Dr. Craig Cogger, WSU Extension Soil Specialist, recommends sandy landscaping fill as a compromise but notes it will not hold much water and will dry out quickly. (True topsoil in our region generally lacks the crumbly structure found in areas with more rainfall.)

Sandy landscaping fill is sandy soil mixed with organic matter (OM). Probably much of what is sold commercially as topsoil in our region is basically sandy landscaping fill. If you decide to purchase sandy landscaping fill or ‘topsoil’ for your raised beds, ask where the soil came from and what it contains.

Buy your soil or fill from a reputable company. Not all soils sold as ‘topsoil’ should be used in raised bed gardens. They can contain broken glass, too many rocks, wood waste, and other debris. Inspect the topsoil before your buy it and before you accept delivery. You also do not want soil that may have come from an area that was treated with long-term residual herbicides or other chemicals.

Ask if the company has had the topsoil tested or knows how much OM it contains. If the topsoil or landscape fill already contains 10 per cent or more OM by volume (5 per cent by weight), you do not need to add compost or other OM. Dr. Linda Chalker-Scott, WSU Extension Horticulturist, indicates that 10 per cent OM is adequate from a fertility perspective. Adding substantially more OM to the soil contributes to high nutrient levels that can lead to plant health problems. Chalker-Scott recommends before adding organic amendments to the soil in your beds, have it tested to determine the OM content and nutrient levels.

Finally if the soil in your beds is distinctly different from the native soil beneath, it can impede drainage. Cogger recommends mixing the introduced soil with your native soil as you build the bed to create a textural gradient that will allow for better drainage. For more on raised beds consult WSU Extension Fact Sheet FS075E at http://cru.cahe.wsu.edu/CEPublications/FS075E/FS075E.pdf

Published: 7/4/2014 11:40 AM

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