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Gardening in Washington State

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Is wood chip mulch a fire hazard?

Coarse textured organic mulches, like wood chips, are the least flammable of the organic mulches. Fine textured mulches are more likely to combust, and rubber mulch is the most hazardous of all tested landscape mulches. If organic mulches are kept moist, they are less likely to catch fire. If you use flamers for weed control in areas near wood chips, be sure to soak the mulched area first.

arborist chips 2
Photo credit: Linda Chalker-Scott

For more information on wood chip mulches, see “Using Arborist Wood Chips As a Landscape Mulch” WSU Extension Fact Sheet FS160E Publications/FS160E

Submitted by: Linda Chalker-Scott, July 20, 2015


When is my garlic ready to harvest?

After the leaves on the lower third of the plant have turned yellow, garlic is ready to harvest. This usually occurs during late June and mid-July depending on the growing climate and the garlic variety planted. Be careful not to damage the bulb during harvest—any wounds or bruises make the bulb more susceptible to disease and deterioration during storage. Use a trowel or spade to gently loosen the soil under the bulb. Remove any soil from the bulb and its roots gently. Place the garlic with the tops intact in a dry, cool, well- ventilated place to cure. Store in mesh bags, braided, or in hanging bunches. After several weeks, the garlic will be cured. To prepare the garlic for use, cut the tops to roughly 1 inch and trim the roots. After curing, the garlic will keep for several months.


Photo credit: Linda Chalker-Scott

For more information on how to grow garlic in your home garden, see WSU Extension Factsheet FS162E, “Growing Garlic in Home Gardens

Submitted by: Sheila Gray, July 13, 2015


Avoiding Strangely Shaped Knobby Potatoes

While growing potatoes is relatively easy, maintaining an even soil moisture is crucial to producing a good crop of well-shaped potatoes. After the plants emerge, potatoes need about 2 inches of water per week, depending on the weather and the type of soil. Regular irrigation will be needed if natural precipitation is not adequate. Wide fluctuations in soil moisture will cause uneven tuber development leading to potatoes with knobby growth, pointed ends, or a dumbbell shape, depending on when the water-stress occurs.


This material is excerpted from the WSU publication Growing Potatoes in Home Gardens FS118E

Submitted by: Marianne Ophardt, July 6, 2015


Do plants get chicken pox? Help!!

Have you ever wondered what causes the spots on your salal bushes?

Photo by  Linda Chalker-Scott

Landscape Plant Problems: A Pictorial Diagnostic Manual will help you identify all kinds of plant problems so that you can take steps to eliminate them. Vivid photos from real-life Northwest landscapes illustrate signs and symptoms of disease, insects and mites, and cultural or environmental problems as they occur on 78 popular ornamental and fruit-bearing plants. A special section shows problems common to a larger number of plants and signs of herbicide damage. The introduction provides five simple steps to identify and diagnose the cause of plant problems. Learn to use the clues WSU experts teach Master Gardeners.

You can order this spiral-bound manual (MISC0194) from WSU Publications. It sells for $35 plus tax and shipping. You may also be able to buy it at your County Extension office

Submitted by: Carrie R. Foss and Jenny Glass, June 22, 2015


Beneficial Predators of Aphids Found in Fruit Trees

For nearly every plant in the home landscape, there is an aphid species that feeds on it. Fruit trees are no exception. Apples host a green apple aphid, cherries host a black cherry aphid (Myzus cerasi), and peaches and nectarines host a green peach aphid (M. persicae). While aphids rarely damage the fruit itself, they can compromise the health of a fruit tree, reduce the size of the fruit, and deposit a sticky substance called honeydew on the surface of fruit and leaves.

Green peach aphid
Green peach aphid. Photo by Mike Bush

There are many beneficial insects that graze on aphids, and in most years, these natural enemies do a fair job of keeping aphid populations in check. Beneficial insects include lady beetles, lacewings, syrphid flies, and parasitic wasps that sting and lay eggs in aphids. Learn to recognize these beneficial insects and conserve them. Many types of beneficial insects can be drawn to the home landscape by planting certain flowers in the yard, such as asters and legumes, as ground cover beneath the fruit tree. Perhaps one of the best ways to conserve these biological agents is to minimize pesticide use. Organic pesticides products should only be used when necessary to protect the fruit and maintain the health of your tree.

Lady beetle larva
Lady beetle larva. Photo by Mike Bush

For more information on organic management of tree fruit pests see the WSU Extension manual EM066E- Organic Pest and Disease Management in Home Fruit Trees and Berry Bushes by Drs. Charles Brun and Michael Bush on-line.

For more information on beneficial arthropods in the home landscape, see the WSU Extension manual EM067E- Beneficial Insects, Spiders, and Other Mini-Creatures in Your Garden: Who They Are and How to Get Them to Stay by Dr. David James on-line.

Submitted by: Michael R. Bush, June 8, 2015


Blossom-end Rot of Tomato and Pepper

Blossom-end rot is a plant disorder that appears as a water-soaked, light brown spot on the blossom end of the fruit. As the fruit matures, the spot becomes sunken, leathery, and brown to black. Opportunistic pathogens can infect this spot leading to fruit rot. Blossom-end rot is associated with a lack of sufficient calcium in developing fruit. Often the disorder is only noticeable on the earliest maturing fruit of the season. Blossom-end rot may be traced to excessive soil moisture, drought stress, or excessive fertilization. Prior to planting next year’s crop, send a soil sample in for testing. Your county extension agent can recommend soil-testing laboratories in your area. If your soil is low in calcium, use lime or dolomite lime at least 2–4 months before planting. Plant in well-drained soils and water consistently. Mulching plants may be helpful. Fertilize moderately to avoid buildup of salts in the soil and to prevent excessive growth.

Blossom end rot on tomato Blossom end rot on pepper
Blossom end rot of tomato (left) and pepper (right)

Crops affected: Tomato, pepper, eggplant, and various cucurbits.

For more information on tomato blossom-end rot, see Growing Tomatoes in Home Gardens FS145E as well as WSU Hortsense

Submitted by: Michael Bush, June 8, 2015


Garden Tip: WSU Master Gardeners can help you solve plant problems

You gaze out at your garden and notice your rose has yellow leaves.  Suddenly you realize your plant has a problem and you don’t know what to do to fix it.  It’s time to turn to your WSU Master Gardener Volunteer diagnostic clinic for help.

Rose virus

Where do you find your local Master Gardener diagnostic clinic?

Each WSU county with an active Master Gardening community has volunteers that provide diagnostic help.  See for your local program.

What type of your sample should you bring?

The plant problem sample you collect to bring to a diagnostic clinic should represent the types of damage you are seeing on the plant.  Since the WSU Master Gardener volunteer will likely not be able to visit the site, you may want to take some pictures to demonstrate the distribution of the problem on the plant and how the plant is situated in the garden or landscape.

What information should you provide?

Come prepared to answer questions.  You will be asked questions about the history and care of the plant as well as the onset of the problem.  The Master Gardener volunteers may also quiz you about environmental conditions and the landscaping practices used.

Source: Excerpted from WSU Plant Problem Diagnosis web page at .

Submitted by: Jenny Glass, June 2, 2015


Growing Green Beans in Home Gardens

Homegrown beans are fresh, nutritious and relatively easy to grow, making them a good choice for first-time gardeners. Edible-pod beans were once called “string” beans, due to the stringy fiber along the seam of the pod. Modern varieties are mostly free of tough fibers allowing the pod to snap into segments easily for cooking or preserving, thus the name “snap” bean. There are a few cultivars of snap bean with yellow or purple-colored pods. Usually, the purple color fades during cooking, revealing a green pod. Harvest green beans for their edible pod when the seeds start to form, but before they begin to bulge, keeping the seeds tender and sweet.

green beans

Green bean photo source: Jeremy Keith, UK, via Wikimedia Commons

For more information on growing green beans in your home garden, go to

Submitted by: Sheila Gray, May 29, 2015


Growing Tomatoes

Washington or high elevations in eastern Washington because fruit needs to reach maturity quickly in cooler summer temperatures. Varieties that have longer growing seasons are better suited to the warmer summer temperatures of eastern Washington.

cover tomato photo

Tomatoes can be very temperamental, and if not cared for correctly, you can end up with few fruit or mostly green tomatoes.  Water is key to a healthy plant.  Expect to water about 1” per week during peak tomato growth. Using a mulch will help reduce water loss.  Overwatering can cause increased leaf growth at the expense of tomato fruit.  Too much water also encourages disease problems.

For more information, please see

Submitted by: Gary Fredricks, May 26, 2015


Growing Cucumbers

Be sure to select a variety that matures within the growing season of your geographic area. Most cucumbers require 50 to 70 days from planting to first harvest.

Purchase seed from catalogs and garden centers. It is not recommended to plant cucumber seed that have been saved from the previous year, as they are unlikely to produce the same variety.


When sowing seeds outdoors, germination is best when the soil temperature is at least 55 °F. Seeds can be planted in mid- to late-May, 4 to 5 seeds per hill (mounds of soil) at a depth of 1-inch. Space the hills 4 to 5 feet apart.

When the plants develop two to three leaves, thin the plants to three well-spaced plants per hill. Cucumbers grow best when temperatures are between 70 and 95 °F. Cucumbers are frost-tender vegetables, meaning frost will kill the plants.

For more information on this topic, see for a free, downloadable PDF.

Submitted by: Sheila L. Gray, May 22, 2015


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