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Avoid Invasive Plants

An article on urban bullies threatening our garden ecosystem.

By Tanya DeMarsh-Dodson and Sarah Reichard

How can people take responsibility for their role in the dynamic of plant distribution on this earth? This is a question that is becoming more and more critical as humans and their landscapes, both agricultural and ornamental, become ever more encompassing of the earth’s surface. Many introduced plants escape gardens and impact wildlands changing the flora and thus the fauna inhabiting those wildlands. In fact, estimates are that about 65% of invasive plants in wildlands were originally introduced as garden plants.

The Washington State Nursery and Landscape Association (WSNLA) has developed a booklet to foster awareness about non-native invasive plants. A task force from WSLNA worked on a project with a select group of nurseries in Western Washington who trialed the Voluntary Codes of Conduct for Nursery Professionals, developed at a workshop at the Missouri Botanical Garden. The goal of this project was to test how nurseries could aid in avoiding the use of plants identified as invasive or potentially invasive. The experience of the nurseries in the pilot project to provide non-invasive alternatives to invasives was assessed so that other nurseries could learn methods by which it is possible to remove invasive plants from the marketplace.

The first step was to assess some species and determine their invasive ability in Western Washington. Using methods modified from those originally developed by The Nature Conservancy, four species were selected for the pilot project: Buddleia davidii (Butterfly Bush), Foeniculum vulgare (Fennel), Hedera hibernica and selected Hedera helix cultivars (Atlantic Ivy and select cultivars of English Ivy), and Ilex aquifolium (English Holly). Do you have any of these plants in your garden? Do you know if the cultivars you are growing are those which are not invasive? It can be an interesting process learning what you have growing in your garden and what plants you might grow which will not escape your landscape. There are an almost endless variety of plants you can grow for food and ornament which are not invasive.

As a gardener concerned about the responsible use of plants for ornament and the table, you can have an enormous impact on whether invasive plants are sold in local nurseries. You can support the removal of invasives from retail sales by asking that the people from whom you buy plants be informed about the behavior of the plants they sell both in your garden and beyond. Horticulturalists are interested in providing their customers with the plants they desire, and if you ask questions about the invasive potential of the plants you purchase, then the people at the nurseries you frequent will respond. Employees at each of the participating nurseries will be able to suggest wonderful plants you might use instead of those on the avoidance list, plants which do not have a propensity for escaping into natural landscapes. Additionally you might take samples of the above plants to other nurseries and ask the people there about what alternatives they might suggest and let them know you are concerned about making wise choices for your garden and for the natural world surrounding your garden. 

The people in the horticultural business who were active in this project to make nature-friendly plants available include people from retail nurseries, growers, and wholesale brokers of plants. Briggs Nursery, McComb Road Nursery, Northwest Nurseries, Lovejoy Nursery, Molbaks Nursery, Sunbreak Nursery, and Wells Medina Nursery volunteered to be a part of this project.


This article appeared in the May/June 2005 Seattle Tilth newsletter. Tanya DeMarsh-Dodson coordinated the pilot project and Sarah Reichard is a professor at UW’s Center for Urban horticulture and a member for the WSNLA Task Force. Edited for updates and link accuracy 11/2009.

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