Flora Non Grata

A new state program takes on problem plants and alternatives

YOU WOULDN'T expect widely available, familiar plants to be out-of-control noxious weeds. Unfortunately, two plants I grew (please note the past tense) in my backyard pond turn out to be nasty invaders, a fact politely pointed out to me by Kathy Hamel, an aquatic-plant specialist with the Washington Department of Ecology. Parrot's feather (Myriophyllum aquaticum) is causing big problems in the Chehalis River since runoff from a private pond washed it into the river. And cute little frogbit (Hydrocharis morsus-ranae) is invading wetlands nationwide, proving difficult and expensive to control.

Hamel suggests that if you're tempted to put any plant besides a native one into a pond or stream, even in your own back yard, that you check first to make sure it isn't invasive. Washington state's aquatic quarantine list is available at http://www.nwcb.wa.gov/. If this seems too much trouble, just think that $600,000 of state money — our money — is spent annually on managing invasive, non-native aquatic plants rampaging through our lakes and rivers.

Dealing with invasiveness is challenging for gardeners who have long relied on a plant's natural capacity for self-seeding and spreading. How to choose responsibly among the welter of available plants? The Washington Invasive Species Coalition was recently formed in part to nudge nurseries and gardeners into doing the right thing. Several years ago, the Missouri Botanical Garden hosted a major conference, with resultant guidelines for ethical choices regarding invasives. To help boost use of these "Codes of Conduct," the coalition started a program, funded by the Nature Conservancy, to support nurseries and inform our plant choices. Because nurseries don't like to be told what to sell, the coalition brought in the Washington State Nursery and Landscape Association to plan a positive approach.

The goal is to identify known invaders, then encourage nurseries to offer customers alternative plants with similar characteristics. If you've asked to buy a yellow flag iris (I. pseudacorus) at Molbak's or Wells-Medina nurseries recently, you might well have been steered instead to a Japanese iris (I. ensata), which is equally at home in wet soils, has the same spiky foliage and elegant bloom, but doesn't invade natural areas as does the yellow flag iris. The most requested invasive plant is Buddleia davidii, with honey-scented flowers that attract butterflies. Since the program began, suggested alternatives ceanothus and red-flowering currant have seen increased sales.

The next phase of the program includes identifying more invasives and producing a brochure showcasing alternatives. "It's a pilot program, we're testing the method to see if it works," explains consultant Tanya DeMarsh-Dodson. With evaluations in from five participating nurseries so far, it appears as if recommending alternatives is a practical way to deter sales of some of our state's peskiest invasives. DeMarsh-Dodson admits to a mixed response from nurseries; some greeted the program cheerfully, some are watching cautiously, others refused to participate.

Suspected invaders are identified through a rigorous process established by Dr. Sarah Reichard of the University of Washington Center for Urban Horticulture with help from her students and conservation groups. Other plants identified as a problem in Western Washington are common fennel (Foeniculum vulgare), English holly (Ilex aquifolium) and English ivy (Hedera helix).

Notorious self-seeding Verbena bonariensis and bronze fennel are being looked at for the next round, but only if it's clear they're wreaking havoc in natural areas.

DeMarsh-Dodson points out that bindweed, that most pernicious of weeds, confines itself to urban and suburban gardens, so isn't a problem in wildlands. It is just these sorts of complexities or challenges that the coalition hopes to interpret for nurseries and gardeners, helping us pursue our passion while protecting the world outside our garden gates.

Valerie Easton is a Seattle freelance writer and contributing editor for Horticulture magazine. Her e-mail address is valeaston@comcast.net.