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Montana’s Noxious Weed List

Weed of the Week – Rush Skeltonweed

Thursday, November 4th, 2010

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

Thursday, October 28th, 2010

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.

Weed of the Week – Eurasian Water Milfoil

Thursday, October 21st, 2010

Milfoil is native to Europe and Asia, but was introduced to the United States between the late 1800’s and the 1940’s. It was collected from a lake near Seattle in 1965 and has since been found in many lakes in that area. This plant is primary spread from lake to lake by boats and trailers, with some spread by water birds. It is very difficult to control and unfortunately has recently been found in Montana. There are multiple species of milfoil, which are very difficult to distinguish amongst. Some of these species are native to Montana. Plant experts often rely on DNA to distinguish between species. The noxious species tends to have its leaflets closer together than the native species.

Concerns Milfoil forms very dense mats of vegetation on the surface of water, which drastically changes the ecology of the body of water. It interferes with recreational water activities such as swimming, water skiing, boating, and fishing. The mass of vegetation created by this plant can cause flooding and it creates good habitat for mosquitoes. Milfoil starts growing earlier in the season than most native aquatic plants and therefore shades the majority of them out. This has negative impacts on fish and wildlife habitat. This aquatic invader can also invade fish spawning habitat, clog irrigation intake pipes, and can hinder power generators. It has the ability to reproduce through broken off plant parts at a very rapid rate and can take over an entire lake in 2 years. Once milfoil is established it is difficult if not impossible to eradicate.

Identification Milfoil species are easy to identify as a group because they all have feather-like leaves arranged in whorls around the stem. Identifying individual species is not quite as simple. It is so difficult that for many years Eurasian water milfoil and northern milfoil were classified as the same species. There are a few characteristics that help in separating the noxious from the natives but they cannot always be relied upon. Eurasian milfoil typically has twelve or more pairs of leaflets on each leaf, the leaves tend to collapse around the stem when removed from the water, and the mature leaves are typically arranged in whorls of four around the stem.

What can you do? Preventing the spread of this weed is the most important thing we can do at this point. Pick every fragment off of your boat or trailer and put them in a garbage can. If you see plant fragments on someone else’s boat or trailer tell them about the threat that milfoil possesses. Spreading the word is so important because an entire lake can be infested by just one tiny fragment. Once a lake or river becomes infested there is no way to completely eradicate the invader. Herbicide treatments, diver harvesting or hand pulling (containing all fragments), underwater rototilling, and instillation of bottom barriers are all somewhat successful in controlling the growth of milfoil. If you are interested in helping stop the spread of Eurasian water milfoil learn how to identify and safely remove it, get other people involved in the prevention, and report any aquatic vegetation that you suspect could be the noxious species. If you have any questions about Eurasian watermilfoil or any other plant call your local county weed district.

Visit the MWCA Weed ID pages for additional information and pictures of Eurasian Water Milfoil.

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.

Posts related to: aquatic noxious weeds, Eurasian water milfoil, Montana's Noxious Weed List, Myriophyllum spicatum, Priority 1B weed
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Weed of the Week – Purple Loosestrife

Thursday, October 14th, 2010

This beautiful riparian plant was introduced as an ornamental from Europe in the 1800’s. It was first reported to be a problem weed in the 1940’s. Purple loosestrife is established in nearly every state in the U.S. Purple loosestrife lives in moist, marshy sites. It will inhibit streams, rivers banks, bogs, irrigation canals, lakesides, and drainage ditches.

Concerns Though this plant is very beautiful it is very problematic for aquatic habitats. Purple loosestrife chokes out native vegetation and creates narrow waterways. The narrowing of waterways increases stream sedimentation and this can negatively affect fish habitat. This weed also negatively impacts waterfowl habitat by degrading nesting sites. Purple loosestrife can easily spread by seed dispersal. A single purple loosestrife plant can produce up to 2.5 million seeds annually.

Identification Purple loosestrife is 4-7 feet tall and can produce many stems per plant. The flowers are a rose-purple color and are clustered along the stem. The flowering stem is spike-like and resembles a lupine panicle. The stems are square to octagonal. The long, narrow leaves come off the stem oppositely. This plant is sometimes confused with native fireweed.

What can you do? Prevention is the most important tool in the fight against the spread of purple loosestrife. Prevent disturbances in wetland areas because this is where purple loosestrife thrives. It is important that purple loosestrife plants be detected early before they are able to spread out of control. Cutting is relatively ineffective, it will decrease the spread of seeds but will not kill the plant. Hand pulling can be done on small patches and is mildly successful. Reseeding should occur after a treatment. A biological control does exist for large infestations. There are leaf-eating beetles and root-mining larvae that are known to help reduce the outbreak of purple loosestrife. The most efficient method is herbicide application. Herbicide application on this weed should be used with extreme caution due to the plants proximity to water sources. For more information and guidance on your weed issues call your local weed district.

Visit the MWCA Weed ID pages for additional information and pictures of purple loosestrife.

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.

Weed of the Week – Field Bindweed

Thursday, September 23rd, 2010

Field bindweed was introduced from Eurasia in the 1800’s. It is unclear whether this weed was brought here as an ornamental or by accident. Other common names that field bindweed is known as are: perennial morning glory, creeping jenny, bellbine, sheepbine, and corn-bind.

Concerns This perennial weed will grow into a dense tangled infestation. Field bindweed will inhabit pastures and cultivated fields as well as other disturbed areas. The creeping nature of bindweed forces out native grasses and forbs creating pure fields of field bindweed. Field bindweed is very difficult to control due to its vigorous root system and its ability to lay dormant for up to 60 years. The roots of the field bindweed can extend up to 15 feet deep.

Identification Field bindweed is part of the morning glory family and shares the family’s vine characteristic. The stems of this weed will grow between 1-4 feet long, creeping horizontally along the ground or climbing fences and other structures. The leaves are shaped like arrowheads, are dark green, and grow alternately along the stem. The most notable feature of this weed are the flowers. They are 1 inch in diameter and are bell-shaped. There are two bracts located on the stem below each white to pinkish flower. Four small seeds are produced by each flower and are located in the round fruit.

What can you do? The control of field bindweed requires a persistent effort. The prevention of new infestations is the cheapest and easiest method for control. Cultivation can be effective if repeated throughout the growing season especially on new infestations. Competitive planting with crops such as alfalfa, cereal grains, and corn have been shown to reduce bindweed growth. Shrubs and trees with vegetation planted below them have also shown to reduce bindweed growth. Landscaping with plastics and fabric can be used in areas where it is conducive. This method excludes light to the plant and may take three years to kill the bindweed plant. There are herbicides that are effective on bindweed. For herbicide recommendations or any weed oriented questions call your local weed district.

Visit the MWCA Weed ID pages for additional information and pictures of field bindweed.

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.

Weed of the Week – Dalmatian Toadflax

Thursday, September 16th, 2010

Dalmatian toadflax was introduced into the west coast of the United States in the late 1800’s. It was brought here from the Mediterranean region as an ornamental plant. It has escaped captivity and now infests much of the northwestern United States. Unfortunately, this weed is still sold in greenhouses as Wild Snapdragon, Butter and Eggs, or Jacob’s Ladder. Dalmatian toadflax was first discovered in south-central Montana in the 1940’s. This weed has been reported in 43 counties throughout the state.

Concerns Dalmatian toadflax is a great concern because it will displace native vegetation and consequently displace animals associated with native vegetation. This weed is extremely successful at displacing native vegetation because it spreads both rhizomatously (roots that run parallel to the ground surface) and by seed. One plant can produce 500,000 seed per year. The loss of native vegetation will also increase soil erosion, sediment yield, and surface runoff due to loss of bunch grasses and sod-forming grasses.

Cattle ranchers are seeing lower carrying capacity on infested sites. Land that has Dalmatian toadflax can have lower appraisal value because of the cost of controlling it and the negative impact the weed has on the land.

Identification Dalmatian toadflax is very similar in appearance to yellow toadflax. The main difference between Dalmatian and yellow toadflax are the leaves. The leaves of Dalmatian toadflax are heart shaped with smooth edges and are arranged alternately on the stem. The leaves and stem are a whitish to bluish in color. The flowers are very similar to yellow toadflax, they are bright yellow with an orange throat and look like a snapdragon flower. Another distinction between yellow toadflax and Dalmatian toadflax is that the Dalmatian can grow up to 3 feet tall.

What can you do? The best strategy for managing toadflax infestations is an integrated approach that focuses on preventing seed formation and vegetative spread. Having multiple approaches to toadflax is crucial because of the wide range of conditions it inhabits and due to its genetic variability. Mechanical methods such as hand pulling and digging are effective in newly established, small patches. Hand pulling toadflax works when the weed is young and the conditions are moist. Mowing will not help reduce toadflax populations because it does not remove the root system. Sheep will graze toadflax when it is in bloom but this is not enough to control an infestation. There are a number of biocontrols being studied; one in particular has shown promising results. This insect is mecinus janthinus and it is a stem boring weevil that causes wilt and suppressed flower production. Herbicides are an effective method for control of toadflax. Revegetation is a very important tool in managing toadflax. Integrating some or all of the above-mentioned tools into a long-term management strategy will help control Dalmatian toadflax infestations. If you have any questions about noxious weeds call the weed district.

Visit the MWCA Weed ID pages for additional information and pictures of dalmatian toadflax.

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.

Weed of the Week – Cheatgrass

Thursday, September 9th, 2010

Cheatgrass is a regulated plant and not a Montana listed noxious weed.

Introduction Cheatgrass is known by a variety of names including: downy brome, downy cheat, and downy bromegrass. Whatever name you know it by you probably know it is one of the most problematic weeds in Montana. Being a winter annual has given it some advantages over other plants. Winter annuals germinate in the fall and continue to rapidly grow until temperatures are no longer conducive of growth. It is possible under certain conditions that growth will continue throughout the winter, especially in the root system. Germination may occur in the spring as well, depending on conditions. Whether or not it continues to grow throughout the winter, fall germination gives cheatgrass a considerable advantage over most of our natives. In addition to this advantage, cheatgrass has an incredibly rapid growth rate. Five weeks after germination cheatgrass has twice the biomass of desirable grasses that have had the same length of time to grow.

Cheatgrass originated in Asia and was accidentally introduced to North American multiple times in several independent events. Some of the first introductions are thought to be from ship ballast and railroad packing materials. The first report of cheatgrass in North America came from British Columbia in 1890. Cheatgrass was first reported in Montana in 1898 in Missoula County and by 1980 every county in the state had it.

Concerns Depletion of soil water is one of the main processes by which cheatgrass competes with perennial vegetation. It is able to deplete soil water before it is available to other vegetation because of its fall germination and rapid growth. The roots of cheatgrass can be much deeper in the soil tapping into the water table and depleting it before other roots have had the opportunity to reach those depths. It is possible that cheatgrass will diminish the underground water reserves and produce seed for the next generation before the hot, dry part of our summers, leaving no water for other plants that are trying to survive and produce seed.

Cheatgrass has a dramatic effect on the fire regimes on grasslands. Cheatgrass has the tendency to fill in the spaces between bunchgrasses, which increases the fuel for fire and promotes larger and more frequent fires. The shortened interval and increases intensity of fires, due to cheatgrass, makes it difficult for perennial vegetation to recover before the next fire. This leads to an increased population of cheatgrass, which in turn leads to more frequent and intense fires. Eventually the perennial vegetation will be removed from the system and a monoculture of cheatgrass will remain.

Identification Cheatgrass plants can be anywhere from 6-24 inches tall depending on the resources available. At emergence the leaves are browish-green. They turn reddish-purple at maturity. The leaf blades, which are covered in soft hairs, are around 1/32 inch wide and 2-6 inches long. The seed-head droops to one side of the stem and has numerous 3/8-5/8 inch long awns (needle-like extension from the seeds).

What can you do? Prevention is the key! If it is too late to prevent cheatgrass from establishing on your property, which it is for most of us, then there are a few other options. The goal behind controlling and ultimately eradicating cheatgrass is to stop seed production. Cheatgrass is an annual, meaning that every plant dies at the end of the growing season. The only way for cheatgrass to persist in an area is for it to produce seeds every year. These seeds are only viable for up to 3 years. This means that if you can stop your cheatgrass from producing seeds for 3 years, you will have a greatly reduced the population. Some ways to stop seed production are: mechanically (hand-pulling, mowing, weed-whacking), chemically (using herbicides – call the weed district for more information), grazing (it is good forage in the early spring for cattle, sheep, and goats), and revegetation (competition is imperative in reducing cheatgrass populations). The integration of all of these tools is more effective than any of the tools alone. Timing is also very important—mechanical control, chemical control, and grazing all must be done before the plant turns purplish-red (once it is purple seed production is too far along and the seeds will still be viable). If you have any questions about cheatgrass or any other weed please call the weed district.

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

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.

Weed of the Week – Spotted Knapweed

Thursday, August 26th, 2010

Notice the dark spots on the bracts under the blossom, this is where the weed gets its name Spotted Knapweed.

Introduction Spotted knapweed is the number one problem on rangelands in western Montana. Spotted knapweed is dramatically interfering with the Montana’s unique ecosystems. It was accidentally introduced to the United States through contaminated alfalfa and contaminated soil used as ship ballast.

The first report of this weed in Ravalli County was 1921. Knapweed has infested 2-5 million acres in Montana, with potential to spread to the 34 million susceptible acres in the state. Spotted knapweed has been recorded in every county in Montana.

Concerns Knapweed has changed the face of our lands in western Montana. Ranchers, wildlife enthusiast, hunters, foresters, hikers, and fisherman are impacted by the dramatic affect that knapweed is having on our ecosystem. Spotted knapweed is particularly hard to manage due to its ability to occupy a variety of sites and habitats. This weed will aggressively out-compete native vegetation.

Watersheds throughout the state are reaping the negative effects of the soil erosion that knapweed causes. The soil erosion caused by spotted knapweed is degrading fisheries and water quality. Spotted knapweed is impacting Montana’s economy in a serious way. The negative effect knapweed has on Montana’s economy is an estimated $42 million annually.

Identification Spotted knapweed is a pinkish-purple flower and the plant grows 1-3 feet tall. The bracts underneath the flowers have dark spotted tips that are also fringed. Spotted knapweed blooms from mid to late July and through September. Each individual flower will bloom for 2-6 days. The flowers will reopen after 20 days to disperse seeds. One knapweed plant can produce up to 1000 seeds and remain viable in the soil for 8 years. You will begin to see spotted knapweed rosettes in early April. Knapweed can grow to nearly 4 feet tall on moist sites.

What can you do? For pastures and rangelands that have not been infested, prevention is key. Avoid transporting seeds from infested sites. Seeds can attach themselves to vehicles, clothes, and animals. Use only certified weed-seed free seed and hay in non-infested areas. For infested areas integrated weed management methods need to be employed. Small infestations can be controlled through timed hand pulling, which should take place when the soil is moist and prior to the plant going to seed. Pulled plants should be bagged and disposed of or burned.

Plowing an infested area is feasible, if plowed down to 7 inches below soil surface and if the area is reseeded with desirable vegetation. Plowing may cause dormant knapweed seeds in the soil to germinate. This method is best if used with herbicide treatment or grazing. Sheep, goats, and cattle will graze spotted knapweed at certain times. Grazing on knapweed should be timed for when the grasses have gone dormant. Sheep grazing in combination with herbicide use can be fairly effective. There are multiple insects that exist in Montana as a mean of controlling knapweed. The success of knapweed eradication requires a long-term commitment.

Visit the MWCA Weed ID pages for additional information and pictures of spotted knapweed.

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.

Hoary alyssum–A weed to watch for on your property

Friday, August 20th, 2010

Dr. Jane Mangold, MSU Assistant Professor and Extension Invasive Plant Specialist, just published an article about a weed to keep an eye out for during the late summer. The following is an excerpt from her article:

Have you noticed a small, white-flowered mustard growing prolifically in your neighborhood? It could be the noxious weed hoary alyssum (Berteroa incana). Hoary alyssum was added to the state noxious weed list in 2008, and may not be as familiar as other notables like spotted knapweed, Canada thistle or leafy spurge.

However, if you live in southwestern Montana, where this weed is most prevalent, you’ve probably seen it along a bike trail or road, in a waste area or pasture, or even in your yard. It flowers from spring through late fall, and is currently very noticeable as other vegetation begins to die back for the season.

Read the complete MSU news article here.

Visit the MWCA Weed ID pages for additional information and pictures of Hoary alyssum.

Weed of the Week – Common Tansy

Thursday, August 19th, 2010

Common Tansy, photo credit: Jerry R. Oldenettel

Common Tansy is also known as golden buttons and garden tansy. Common tansy was introduced from Europe into colonial North America in the 1600’s as an ornamental plant and for medicinal uses. Ironically, common tansy contains alkaloids that are toxic to humans and livestock if consumed in large quantities. Common Tansy was first discovered in Silver Bow County in 1936. Common tansy is a big problem in most counties on the roadsides, ditches, and waste areas.

Concerns Common tansy is unpalatable to livestock and mildly poisonous. The presence of this weed reduces species diversity, wildlife habitat, and livestock forage. It has a tendency to grow near water, which allows the plant to spread easily and makes control difficult. The root system on common tansy allows the plant to spread laterally and by broken pieces of roots.

Identification Common tansy is a perennial forb that can reproduce by rootstalk or seed. One of the most notable features of tansy is the potent smell cause by crushing the leaves. The flowers on common tansy are yellow-orange button-like flower heads. Flowers of the common tansy are numerous; there can be 20-100 flowers in flat-topped, dense clusters. The leaves on the common tansy are deeply divided into leaflets with toothed margins, almost fern-like. The leaves are alternately arranged and are uniform in size. This plant will grow between 1-6 feet tall and the stem is often a purplish-red color.

What can you do? Due to the extensive root system of common tansy an integrated management approach is necessary. Preventing the spread of this weed into new areas is one of the easiest management techniques. Mowing and hand-pulling has marginal results due to the root system of tansy and they are best used in combination with other controls. Mowing and pulling will help prevent seed production. Maintaining healthy desirable vegetation will aid in controlling common tansy. Grazing in infested areas should be monitored closely to maintain desired species. There are a couple of effective chemicals for common tansy. For recommendations on those, call the weed district,

Visit the MWCA Weed ID pages for additional information and pictures of common tansy.

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.

Montana Weed Control Association

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Montana’s Noxious Weed List

Weed of the Week – Rush Skeltonweed

Weed of the Week – Orange Hawkweed

Weed of the Week – Eurasian Water Milfoil

Weed of the Week – Purple Loosestrife

Weed of the Week – Field Bindweed

Weed of the Week – Dalmatian Toadflax

Weed of the Week – Cheatgrass

Weed of the Week – Spotted Knapweed

Hoary alyssum–A weed to watch for on your property

Weed of the Week – Common Tansy

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