Noxious and/or invasive weeds

Yes, the rumors are true. The Russian olive is on the state’s designated noxious weed list. Russian olives are displacing cottonwood and willow stands within riparian areas. Russian olive-dominated riparian areas are often much less diverse in terms of habitat structure and plant community composition. For control information and cost share, contact your local Weed and Pest office.

Purple loosestrife (Lythrum salicaria) is a European plant species accidentally introduced to North America from Europe in the 1800′s, which is an aggressive invader of North American wetlands, lakes and rivers. Once established, purple loosestrife can become the dominant vegetation, forming a mono-specific stands, which significantly reduce biodiversity and degrade habitat quality. Of primary concern is that purple loosestrife displaces native plants eliminating food and shelter for wildlife and other species. While a strikingly colorful lavender flower, dense stands of loosestrife also impair recreational use of wetlands and rivers, impede water flow in drainage ditches and invade right of ways, requiring costly management efforts. Purple loosestrife is a widespread and serious problem, affecting both coastal and inland wetlands, lakes and waterways. The Canadian Wildlife Service, Ducks Unlimited Canada, Minnesota Department of Natural Resources and the Great Lakes Sea Grant Network have put together a very good web page on this plant.

Purple loosestrife can grow from 3- to 6-feet tall, with a square, woody stalk. The plant leaves have smooth edges, are on opposite sides of the stalk and attach directly to the stalk. The flowers have long pink/purple spikes with a perennial rootstock, which can send from 30 to 50 shoots. Each plant can produce up to 2.7 million seed in one season.

Many organizations throughout North America have taken action to control the spread of purple loosestrife.

National wildlife services, state natural resource and environment agencies, universities, nursery trade associations, and conservation and community organizations have responded to the purple loosestrife invasion by raising awareness of the threat posed by this invasive plant and how to prevent its spread. It is considered a noxious weed in Wyoming. If you look at Little Goose or Big Goose creeks and other drainages around Sheridan, you will see it growing. In addition, purple loosestrife seeds are present in some wildflower seed mixes–check the label before you buy any seed packages.

Be careful when planting wildflower seeds because some wildflower seed mixes contain poisonous plants. These could include Lupine and Larkspur, both have nice flowers and are in lots of gardens and people like to take pictures of these on the mountain, but they can poison livestock. Wyeth lupine (Lupinus wyethii) have palmate leaves with upright showy flower clumps typically purple color but can vary, with the seed pods resembling pea pods.

Larkspur (Delphinium nuttallianum) which is typically a shorter plant with a tuberous root system, with leaves being deeply parted into finger-like lobes. This plant has showy violet lavender flowers with a prominent spur on the end and is also poisonous to livestock. Many other plants may not be poisonous but can spread uncontrollably invasive.

Remember when ordering plants or wildflower seed mixes to look at the content seed list and be knowable of what you are getting. Noxious weeds are to be controlled by state statute and the complete list can be obtained from the Extension Office or the Weed and Pest Office.

Trade or brand names used in this publication are used only for the purpose of educational information. The information given herein is supplied with the understanding that no discrimination is intended, and no endorsement information of products by the University of Wyoming Extension is implied. Nor does it imply approval of products to the exclusion of others, which may also be suitable. The University of Wyoming is an equal opportunity/affirmative action institution.

Scott Hininger is with the Sheridan County Extention office.
 

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