KC Weed News - June 2006  Topics Below
Sometimes it’s hard to know how an invasive plant first gets started, but the history is pretty clear for this lovely but pernicious annual. In 1839, seeds of Impatiens glandulifera were sent from their native home in western Himalaya to the Royal Botanic Gardens in Kew, England. Within 15 years, populations had escaped and naturalized into the English countryside. By the 1900’s, the plant was widespread throughout England and Ireland. Today, it is considered one of Great Britain’s “Top 20” Alien Plants because of its abundance and distribution. Policeman’s helmet, also known as Himalayan balsam or poor man’s orchid, continues to move into new parts of the world with the help of gardeners attracted by the pretty flowers and the naturalistic way it self-seeds in the garden and beyond. It is now naturalized in 31 countries on three continents (Europe, North America and Asia) and is rapidly expanding its range especially in Europe, Eastern Asia and North America. In our region, policeman’s helmet is established in parts of western Washington and the lower Fraser Valley of British Columbia. In King County, we have significant infestations in several areas including Miller Creek in the SeaTac/Burien/Normandy Park area, the Kelsey Creek-Lake Hills Connector area in Bellevue, Peasley Canyon in Auburn, Issaquah Creek south of Issaquah, Thornton Creek in north Seattle, the Mountain View Road area of Duvall, and on Vashon Island. Although this plant is only an annual, it can reach ten feet tall in shaded areas, shorter in sunny spots. Pretty pink-purple to white flowers are present from June to October (shaded plants flower later) and seeds set within 13 weeks after flowering. When the seed capsules mature, they split open and eject around 800 seeds as far as 20 feet away. The seeds travel along waterways and can germinate under water. They stay viable in the soil for about two years. Because of its shallow root system, policeman's helmet can be easily pulled. However, its stems will root and re-grow if left on the ground, so pulled plants should be dried or piled on tarps to compost. Seeds last in the soil for about two years, so at least two years of follow up monitoring is recommended. Besides showing up near gardens, policeman’s helmet has escaped into moist lowland forests, streamsides, and roadside thickets. No longer legal to sell in Washington State, policeman’s helmet remains a favorite trading plant among gardeners, who often find themselves with numerous volunteers to share with their friends and neighbors. This plant is a strong competitor and can reduce the fitness of native plant species and eventually replaces them in invaded sites. Left alone, this plant will continue to spread into riparian areas and to push out beneficial native plants. Because of the potential damage that policeman’s helmet can do especially in streamside habitats, please contact the King County Noxious Weed Program if you spot any policeman’s helmet in the county at 206-296-0290. Weeds in Bloom: Noxious Weeds to Look For in June Going to Seed : Garlic Mustard, Gorse Flowering Now : Milk Thistle, Dalmatian Toadflax, Orange Hawkweed, Yellow Hawkweed, Common Hawkweed, Meadow Knapweed, Spotted Knapweed, Spanish Broom Will Flower Later in June : Sulfur Cinquefoil, Giant Hogweed, Goatsrue, Perennial Pepperweed, Diffuse Knapweed, Tansy Ragwort, Policeman’s Helmet June 1 - Knotweed Control Workshop and Demonstration Tackling knotweed can be a daunting task but the benefits are truly rewarding. Our program will be holding a hands-on training on knotweed control that will include how to use different methods, where they work best, and how to develop a coordinated knotweed management plan to improve your chances for success. We will be demonstrating control methods on real live knotweed. This workshop is being hosted by Dave Olson, a homeowner on the beautiful South Fork Snoqualmie River who is working toward his vision of a knotweed-free river. For more information or to register, contact Sasha Shaw, 206-263-6468, sasha.shaw@kingcounty.gov. The workshop is June 1, 6:30-8:00pm and it is free and open to the public. Pasture Weed Workshops Worried about weeds? Come to one of our pasture weed workshops this June to learn how to identify and manage troublesome weeds coming up in your fields and farms. The workshop will provide information on plants that damage pasture quality and livestock health and how to manage weeds in pastures. Bring your weeds to show and tell and bring your questions to “stump a weed expert”. To register, please contact Sasha Shaw at 206-263-6468 or sasha.shaw@kingcounty.gov. Dates, Times and Locations: - June 8, 7 pm, Snoqualmie’s Meadowbrook Farm
- June 14, 7 pm, Auburn Library
- June 20, 7 pm, Enumclaw Library
- June 27, 7 pm, Vashon Land Trust
Poisonous Noxious Weeds For anyone who has worried about what plants their children may be eating or what’s growing in their pastures, poisonous plants are a frightening problem. When our daughter first started crawling through our garden and I started to do research on toxic plants, I was stunned by how many ordinary garden ornamentals are poisonous. If you delve even more deeply into plant science, you will discover an amazing array of toxins produced by plants of all sorts, some of them quite lethal and others more insidious that cause illness slowly over long periods of exposure. Fortunately, most animals, including people, avoid the plants that taste or smell bitter. These warning tastes and smells lead us and most animals away from the majority of toxic plants. However, in those cases where plants are mixed in with food sources like hay or hard to avoid such as in over-grazed pastures, grazing animals are more likely to be exposed to dangerous concentrations of toxins. Likewise, when plants are growing where small children are playing, especially near edible garden plants or berries, the risk of exposure increases. And finally, if a toxic plant is also very difficult to control and highly invasive, the problem is magnified even more. This is the case with poisonous plants that are also noxious weeds. Noxious weeds that are a threat to people include: giant hogweed (the sap causes burns and blisters), poison-hemlock (whole plant is poisonous) and bittersweet nightshade (whole vine is poisonous especially the unripe green berries). Noxious weeds that can poison livestock include poison-hemlock, tansy ragwort (accumulates in the liver and can cause death), common groundsel (tansy ragwort relative often found in hay), milk thistle (causes nitrate accumulation), and goatsrue (uncommon in King County but one to watch for). Fact sheets on all these plants as well as a list of poisonous plants of Western Washington that affect livestock can be found on our brochures page. There are also many excellent websites on poisonous plants including: Cornell University’s Poisonous Plants Database, USDA Poisonous Plant Research and King Conservation District’s local list of plants poisonous to horses. My favorite book for researching toxic plants is called Common Poisonous Plants and Mushrooms of North America by Nancy J. Turner and Adam F. Szczawinski, published by Timber Press. There are many more resources available and, of course, if you ever suspect exposure to a toxic plant, contact your doctor or veterinarian immediately or call poison control at 1-800-222-1222. If someone has collapsed or isn’t breathing, call 911. Miller and Walker Creek Riparian Weed Project The King County Noxious Weed Program received an award of $35,000 on May 23 from the Port of Seattle to survey and control noxious weeds along Miller and Walker Creeks in the cities of Burien and Normandy Park. These funds will be matched by contributions from the program. The program has been working with landowners in these watersheds since 2000, and in 2002 identified a streamwide infestation of policeman’s helmet (Impatiens glandulifera) on Miller Creek between the Cove (where control work was already being done) and the Port of Seattle properties in SeaTac. This infestation travels downstream and the level of its impact to each individual property on Miller Creek has increased each year. Since then, 5 additional serious riparian weed species have been found on Miller and Walker Creeks: purple loosestrife, giant hogweed, perennial sowthistle (found at the Cove), and invasive knotweed. These weeds are currently creating significant environmental impact in terms of displacement of native riparian vegetation, reduced habitat and faunal support (including to endangered salmon) and altered hydrology. The grant will fund a watershed-wide, coordinated approach to their control. Without intervention, these problems are highly likely to expand and intensify. Work is scheduled to commence in June. Workshops on invasive weeds and how to restore infested properties will be held for residents of Normandy Park on June 17 and for Burien and SeaTac residents on June 24 at the Burien Library. For more information on the project or the workshops, please contact us at 206-296-0290 or noxious.weeds@kingcounty.gov. Seattle ’s Forests – Native but for how much longer?? The recent Citywide Habitat Assessment Interim report by the Seattle Urban Nature Project (SUNP) reveals some disturbing trends about the state of Seattle’s native forests. The study sampled two forest types in the City – conifer/deciduous mixed forest and conifer/madrone mixed forest. The regenerating tree layer consisted of 65% and 68% non-native trees in each of these forest types respectively. The picture is just as bad in the understory. English Ivy covered 28% of the area and was present on 89% of the plots in conifer/deciduous forests, and covered 12% of the area and was present on 100% of the plots in conifer/madrone forests. The study compellingly shows that the “do nothing” scenario of letting the forests manage themselves will produce radically different forest communities than the ones we enjoy today. Many of these weeds established when our knowledge of their impacts was less complete and their slow rate of spread and establishment escaped our attention. Today, we cannot use ignorance as an excuse. The report is available at Seattle Urban Nature.
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