MWCA Library » invasive species

Weed of the Week – Rush Skeltonweed

MWCA — Thu, 04 Nov 2010 07:06:01 +0000

Rush skeletonweed was accidentally introduced in the U.S. in the early 1900’s. It was first discovered in Spokane, Washington in 1938. Today, Idaho and Washington have serious infestations of this weed. In Montana, Lincoln and Sanders Counties are battling sizable infestations. The Montana Department of Agriculture has spent around $500,000 trying to control Rush skeletonweed in these counties. It is extremely important for this plant to be located and eradicated before it is capable of spreading.

Concerns Rush skeletonweed is a very difficult plant to control and it spreads very easily. Seeds of this plant have been documented to travel up to 20 miles from the original plant via wind. The taproot of this weed can be 7 feet long and the roots can also spread laterally. These lateral roots and root fragments can start new plants. It also out competes native vegetation and creates poor wildlife habitat.

Identification The bright yellow flowers of this plant are found in clusters of 2-5 blooms. The sharp toothed leaves, which are similar to those of a dandelion, only occur at the base of the plant. The stems of this plant are completely leafless but the base of the stem is covered with downward facing, coarse, brown hairs. When this plant is broken off a milky substance will ooze out. This long-lived perennial can grow to be up to 4 ft tall and can produce up to 20,000 seeds at a time.

What can you do? Large infestations of Rush skeletonweed are just over the border in neighboring states. It is very important to take measures to prevent the spread of this weed into our county. These seeds can be spread by traveling through infested areas and transported on vehicles, machinery, clothing and animals. Prevention and immediate eradication is the goal for managing Rush skeletonweed. Small infestations can be controlled by hand-pulling and digging, done diligently throughout the year and for up to 10 years. Pulled plants should be burned to destroy the seeds and root system. Mowing is ineffective because it will not sufficiently stress the plant. Tillage will not work; it will spread the plant further. There are several chemicals that are recommended for the control of Rush skeletonweed and for a list of these call your local weed district. There are three biological controls used on Rush skeletonweed and the most wide spread is a gall midge; this midge reduces seed production and deforms the plant. If you have any questions about Rush skeletonweed please do not hesitate to contact us.

Visit the MWCA Weed ID pages for additional information and pictures of rush skeletonweed.

This articles was developed by Ravalli County. If you would like to use this article please contact Ravalli County Weed District Weed Coordinator at (406) 777-5842.

Weed of the Week – Orange Hawkweed

MWCA — Thu, 28 Oct 2010 07:49:54 +0000

Orange hawkweed is native to Europe and likely came to the U.S. as an ornamental. It has since escaped cultivation and was first found to be a problem in Spokane, WA in 1945. There are serious infestations in northwestern Montana, northern Idaho, and northwestern Washington.

Orange hawkweed’s clusters of bright orange to orange-red dandelion-like flowers make it unmistakable. The orange flowers follow the path of the sun throughout the day and if the plant is broken off it exudes a milky latex substance. There are several native species of hawkweeds in Montana but orange hawkweed can be distinguished by its orange flowers (it is the only species with orange flowers), bristly hairy leaves (most other species have smooth leaves), and stiff black hairs up the stem.

Concerns Orange hawkweed is a great concern because of it ability to reproduce several ways. The clusters of 5-30 flowers produce between 12 and 50 seeds per flower and these seeds remain viable in the soil for up to 7 years. This plant can also spread or reproduce from stolons (above ground runners), of which it produces an average of 6 per year, rhizomes (underground horizontal roots), or adventitious root buds (buds on the roots that can develop into a new plant at any point). Not only does it have the ability to spread in a variety of ways but it is also believed to be allelopathic (exudes toxic chemicals into the soil that suppress surrounding vegetation). The combination of these abilities makes it a very aggressive species that can rapidly create large, dense monocultures pushing out not only native, beneficial vegetation but also established lawns.

Identification This perennial has a basal rosette with many hairy leaves and a leafless, hairy stem that can be up to 30 inches tall. Each rosette is capable of producing 10-30 flower stems, each of which have 5-30 orange flowers that are arranged in a flat-topped cluster. The flowers are bright orange to orange-red and dandelion-like in appearance, with square ended petals.

What can you do? Due to the extensive root system of orange hawkweed hand-pulling and digging-up large infestations is not an effective means of control. Very small infestations may be controlled by these methods but care must be taken to remove all of the root system because even the smallest fragment can produce a new plant. Mowing is not recommended because it actually encourages the growth of this plant. There are several herbicides that are effective in controlling orange hawkweed and re-seeding is always recommended to fill in the areas where this plant was removed. If you have any questions regarding orange hawkweed or any other weed call your local weed district.

Visit the MWCA Weed ID pages for additional information and pictures of orange hawkweed.

This series of articles was developed by Ravalli County. If you would like to use these articles please contact Ravalli County Weed District Weed Coordinator at (406) 777-5842.

Transportation of Spotted Knapweed Seeds by Vehicles

MWCA — Wed, 27 Jan 2010 16:03:41 +0000

Vehicles have long been suspected of being a major distributor of spotted knapweed seed. The purpose of this experiment was to determine how many seeds could be disseminated by vehicles and to measure how far the seeds would travel. Sites were chosen at the Story Hills in Bozeman, the old Milwaukee Road rail yard in Deer Lodge and a site near the Bauxendale Volunteer Fire Department west of Helena. At each site, twelve plots each measuring twelve by forty feet were staked and the surrounding area was mowed. A late model pickup truck was driven 40 feet into each plot and backed out. The vehicle was then driven 25 mph for distances of 0, 0.1, 1.0, and 10.0 miles. The vehicle was placed on a large tarp and the entire undercarriage was vacuumed to collect spotted knapweed seeds and plant material. The collected material was bagged to await seed counting. At the Deer Lodge site, over 1633, 510, 226 and 138 seeds remained on the vehicle after traveling 0, 0.1, 1.0, and 10.0 miles. The results indicate that spotted knapweed seed is readily disseminated by motor vehicles for long distances.

Prepared by:

Phil Trunkle and Pete Fay
Department of Plant and Soil Science
Montana State University
Bozeman, Montana 59717

Download a PDF version of this document here.

BLM Uses Stimulus to Remove Russian Olive

MWCA — Fri, 22 Jan 2010 18:36:14 +0000

On January 20th, the Billings Gazette featured an article about the BLM removing Russian Olive trees.

The trees were introduced as a fast-growing, hardy tree good for creating shelter belts, habitat and food for wildlife. Russian Olive tree is indigenous to Europe and Asia. It can quickly colonize in riparian areas and out compete native vegetation, interfere with natural plant succession and nutrient cycling. Read the full article about the Bureau of Land Managements efforts.