Tips to avoid spreading noxious weeds

Marianne Ophardt, Washington State University Benton County ExtensionNovember 22, 2013 

Last week I talked about two noxious weeds that gardeners share some responsibility for introducing and spreading throughout the U.S. This week, I will discuss our duty as gardeners to avoid spreading potential noxious weeds.

More than five years ago, I noticed a new plant being sold at local plant sales. It was called "donkey tail" or "burro tail." More officially, it's known as myrtle spurge (Euphorbia myrsinites). It is a low-growing perennial with trailing fleshy stems and looks similar to noninvasive garden spurges.

The waxy, fleshy leaves of myrtle spurge are blue-green and arranged alternately along the stem, giving the plant an interesting spiraled appearance. The yellow flowers at the tips of each stem are not showy, but bring some color to the plant in the spring.

Myrtle spurge was introduced for use in rock gardens and xeriscapes because it is easy to grow and drought tolerant. However, it has many things that shout "don't plant me." As a noxious weed, it is invasive and displaces native vegetation. In addition, all parts of the plant are poisonous if eaten, causing nausea, vomiting and diarrhea, even though animals usually avoid eating it. Gardeners should note that as a member of the Euphorbia family, its milky sap causes severe skin irritation and blistering.

While myrtle spurge is not a problem in agricultural crops, it has escaped cultivation in parts of Washington and moved into sensitive ecosystems. It can be controlled easily in agricultural land and gardens with frequent cultivation. If you find a patch, rogue out. Because of the caustic sap, wear safety goggles, gloves and long sleeves.

When I saw myrtle spurge being sold, I wondered why this plant is so plentiful that gardeners had lots to share. That can be a clue to a plant's tendencies to be invasive, even if it isn't on a noxious weed list. Remember, the Washington Noxious Weed Board estimates that at least half the weeds on its list are escapees from gardens, problems that could be avoided if gardeners and the horticulture industry were better informed.

So what can we do? Adhere to a voluntary gardening code of conduct.

1. Don't sell or trade plants with other gardeners that you know to be invasive, aggressive or hard to control. Not all of these are noxious weeds, but sharing plants with bad behavior is not an honorable practice.

2. Talk to your local garden center or nurseries, and encourage them not to promote or sell invasive plants.

3. Occasionally, check state (www.nwcb.wa.gov) and local noxious weed lists for plants on the watch list. Share the information you know about noxious weeds, aggressive or invasive plants, and poisonous plants with neighbors and friends.

4. Do your research before you plant. Make sure a plant is friendly to our region's ecosystem and not invasive. If you discover you have already planted a problem plant, remove it and replace with a similar plant that won't cause problems.

-- Marianne C. Ophardt is a horticulturist for Washington State University Benton County Extension.

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