Vashon's pretty invader: Policeman’s helmet

2004 Archived News

Have you noticed a 5 to 10 foot tall plant with pink flowers resembling an English policeman's helmet growing in shady, wet areas of Vashon and Maury Island? If so, King County's Noxious Week Control Program wants to know.

Policeman's helmet (Impatiens glandulifera) is a very fast growing annual from India and the western Himalayas. Yes, it is actually an annual that can grow over 10 feet tall. Introduced as a garden ornamental, it has escaped cultivation to become an invasive noxious weed. Though illegal for sale, seeds are often traded among gardeners who are unaware of the aggressiveness of this plant. Policeman's helmet spreads quickly with its ability to shoot or project its seeds 15 to 20 feet from the mother plant, and can grow in every amount of light from heavy shade to full sun. This plant has already colonized much of England, where the climate is much like ours. It is considered to be one of the "top 20" British alien plants because of its abundance and distribution. In Washington it is a noxious weed, and control is required in King County. Policeman's helmet competes with native plants for pollinators, reducing the seed set of native plants, and it crowds out native wetland plants.

The King County Noxious Weed Program is currently aware of just over 100 sites, the largest in Bellevue and Auburn, with smaller sites on Vashon, in Seattle and in Duvall. The Noxious Weed Program works with landowners to remove this plant. The good news is that policeman’s helmet is very easy to pull. Sites that have been worked on have fewer plants than they used to and native species are making a comeback. The bad news is that each plant can produce from 800 to 2,500 seeds, generating a mass of seedlings the following year that crowd out and replace native and beneficial plants.

Other distinguishing characteristics of policeman's helmet include a hollow, fleshy stalk with leaves that are opposite or sometimes whorled around the stem, with usually three leaves to a node. The leaves can be 6 inches long, and the leaf margins are toothed with 20 "teeth" or more along each side. If you look closely, you will notice small glandular stalks found at the base of the leaf stems. Adventitious roots are often found along the lower stem nodes, sometimes buttressing, helping policeman's helmet to adapt to very wet areas and root very shallowly.

Help us track this weed to keep it out of Vashon's streams and natural areas! Please contact the King County Noxious Weed Control Program at 206-296-0290 or send an e-mail to noxious.weeds@kingcounty.gov.

For more photos and information on Policeman's Helmet or other noxious weeds, please come by the Noxious Weed information table July 10-11 at the Strawberry Festival, call 206-296-0290; e-mail noxious.weeds@kingcounty.gov; or visit the Web site . To report a noxious weed infestation in King County, call the program or use the online form at http://dnr.metrokc.gov/wlr/lands/Weeds/infestations-form.cfm.