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Gardening in Washington State

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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


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


Organic fungicides

Plant diseases caused by fungal pathogens are very common in home gardens in the Pacific Northwest, particularly west of the Cascade Mountains. Spring rains combine with warm temperatures and tender new plant growth to create ideal conditions for fungi to thrive and spread. Common fungal diseases seen in home gardens include powdery mildew, downy mildews, rusts, and late blight. Fortunately, there are many products available to home gardeners for managing diseases caused by fungal pathogens on plants. This fact sheet describes organic fungicides and provides information on:
• which organic fungicides are legal and available to home gardeners,
• how effective these organic fungicides are, and
• whether the products have unintended effects on people or the surrounding environment

Copper sulfate

More information is available on this free, downloadable fact sheet:

Submitted by: Linda Chalker-Scott, May 15, 2015

Lime-sulfur Spray Availability for Home Gardeners

Background Situation:

Home gardeners in Washington State haven’t been able to buy lime sulfur spray in recent years. Lime sulfur had been used for years to control fungi on roses, fruit trees and ornamentals.

There is a reason lime sulfur hasn’t been available. In early 2008, EPA questioned whether lime sulfur was so caustic that it should be reclassified as a restricted-use chemical. Only people with pesticide licenses can buy restricted-use products. This would be a problem for home gardeners; they don’t have licenses.

In April 2008, Lilly-Miller voluntarily cancelled its Dormant Spray® registration with EPA. Bonide Products, Inc., which made a similar lime sulfur product, cancelled their registration at the same time.

EPA gives retailers up to a year to sell their shelf stock in these situations. Retailers continued selling home garden lime sulfur products until May 2009. WSDA continued to register these products, and PICOL continued to list these products, through December 2010.

The confusion happened in summer 2009, when Washington State gardeners couldn’t find lime-sulfur products on store shelves even when the products were registered.

Lime sulfur is a modified form of elemental sulfur.

Lime sulfur is a modified form of elemental sulfur.

Product Update:

In 2013, Lilly-Miller registered a new home garden product with lime sulfur: Polysul®. Another company, Voluntary Purchasing Group (VPG) also registered a lime-sulfur product but it’s both a home garden and commercial use. Recommending these products requires a Washington State pesticide license. So WSU Master Gardeners cannot recommend the VPG product.

It isn’t known if stores in Washington State sell either product. Home gardeners who bought and still had earlier lime sulfur products can use them until gone.

Bottom Line:

Home gardeners may have trouble finding lime sulfur products. Master Gardeners can recommend lime sulfur products as one of several management options if and when suggested by WSU Hortsense.

Additional Resources:

WSU Hortsense fact sheets ( on pest management.

Federal Register web page for Dormant Spray® voluntary cancellation (pgs. 2 and page 9).

PICOL (Pesticide Information Center Online) database for a list of WSDA-registered labels:

Issued by:

Dr. Catherine Daniels
Washington State Pest Management Resource Service
office: (253) 445-4611
January 23, 2014

Gardening in Washington State, Puyallup Research and Extension Center

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