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SWCD News: Please don’t share your weeds!

It's haying time! Although the farmers have had to dodge the raindrops to get the hay in, the wet weather has been good for grass and gardens. Unfortunately, it's also been good for weeds.

On my recent wanderings, I've noticed fields where the livestock ate the grass but left nice-sized patches of tall weeds. I've also seen hayfields with grass growing back and, again, there were nice-sized weed clumps growing faster than the grass. This has made me really think about weeds….

Just what is a weed? Most think immediately of dandelions, but a weed is anything that is growing where we don't want it to grow — dandelions and grass growing in the garden, buttercups and thistle in the lawn, even mint and strawberries spreading out from their garden beds can be considered weeds. Kelly Smith, conservation technician with Carlton County Soil and Water Conservation District (SWCD), said "volunteer corn can be a weed in a soybean field."

"Some plants can be weeds in one location, but useful plants in another," Smith added. "Trefoil can be a weed in a native meadow, or it can be a useful forage plant in a pasture. The whole topic of weeds is subjective as to what weeds are bad and what are good," as almost every weed, even the dreaded dandelions, are good for something.

Weeds do have their purpose in nature. Exposed soil is considered a “wound” and, according to Smith, Mother Nature "will try to heal her wounds with 'scabs' (weeds) to stop herself from bleeding (soil erosion). Weeds are pioneer species that quickly form scar tissue over wounds," thus giving time for the "skin (grasses, shrubs and trees) to take root and grow."  

Invasive plants are double trouble weeds as they are growing where they are not wanted and they are also not natural to that area. Invasive weeds push out the native plants. If unchecked, invasives spread from field to field, yard to yard, road to road.

In a variety of ways, invasive weeds cause harm to the economy, environment and human health. Most don't know that spreading these weeds, or allowing them to spread, is illegal according to Minnesota Statutes, Section 18.78 and 18.82. In fact, it is illegal to even allow some some types of weeds to even grow.

So, what are some of these invasive weeds invading our crop and hay land? What do they look like? How can we stop them from spreading?

Smith and Will Bomier, district conservationist with the U.S.Department of Agriculture's Natural Resources Conservation Service (NRCS), recommend people check out two great websites that show how to invasive weeds currently in Minnesota and how to control or eradicate them: from the Minnesota Department of Agriculture (MDA) and from the Minnesota Department of Natural Resources (MNDNR).

Tom Gervais, NRCS's regional grazing specialist in northeast Minnesota, said some of the "invasive and/or noxious weeds that are seen fairly often in Carlton County farmland (hay land, pasture, cropland) include common tansy, Canada thistle, bull thistle, and spotted knapweed." Troy Salzer, educator with the Carlton County Office of the University of Minnesota Extension, also added leafy spurge and purple loosestrife to this list. I was surprised as several of these are plants I have seen for years and thought they were natural to our area!

Common tansy (CT) is one most everyone is familiar with. I see it all the time, but never knew it was an invasive species. Originally introduced to the U.S. from Europe for medicinal and horticultural purposes, CT is now widespread across most of northern U.S. and Canada. It was once cultivated in gardens and can still be found in gardens, along roadsides, and in abandoned farms in northern Minnesota.

A member of the marigold family, CT is a perennial with a distinctive smell. It can grow 3-6 feet high and has fern-like leaves and yellow flowers that look like clusters of buttons on top of the stems. It flowers from mid-July to September and spreads through seeds and rhizomes (roots). Through the years, CT has gained a good foothold in Minnesota and will be almost impossible to completely get rid of.

According to Salzer, the best way to control CT is using a multi-pronged approach: pulling plants before they flower, working to improve soil quality, tilling infested acreage regularly, and growing a cover crop to keep the soil covered. These actions will discourage CT and encourage natural grasses and plants. If you have cattle, prescribed (or intense or mob) grazing, which involves turning lots of cattle into a small area for a controlled amount of time (usually 6-12 hours), will help to destroy the plants as the cattle will stomp the weeds down. Sometimes the cattle develop a "taste" for eating tansy and may continue to eat it.

Bull thistle (BT) was introduced to the U.S. in the early 1800s from Europe and Asia. A biennial plant that can grow 3-6 feet tall, BT has one erect branched stem which grow rosettes the first year that bloom the second year. BT flowers bloom from July through August and each flowerhead contains hundreds of seeds dispersed by the wind. These seeds can remain viable in the soil for over 10 years.

Generally not a threat in good, rich soils, BT is very competitive in bare or disturbed soils, such as pastures, hayfields, roadsides and ditch banks. Most grazing animals won't eat BT so it usually spreads unchecked. Some birds, like Finches, love thistle seed and also help spread the seeds.

BT is best controlled by pulling or mowing the plants before they flower. Mowing year after year will weaken the root systems and eventually kill the plants.

Canada thistle (CaT) has spread throughout northern U.S. and into Canada and been declared a noxious weed in 43 states. It is one of the most tenacious agricultural weeds as it spreads quickly and replaces native plants thus diminishing diversity. It can invade natural prairies, savannas, glades and dunes where soil is disturbed. It also invades wet areas with fluctuating water levels, such as streambanks, sedge meadows, and wet prairies.

A perennial that can reach 2-5 feet tall, CaT has numerous small purple flowers that bloom between June and September. Its seeds are dispersed by the wind and can remain viable in the soil for over 20 years. The plant spreads very quickly by seed and root, and one plant's roots can spread 10 to 12 feet in one season alone!

Salzer said CaT can be destroyed by repeated pulling and mowing which will weaken and eventually kill the roots. The best time to mow is when flower buds are just about to open. Prescribed burning is another recommendation. It is best to burn in late spring (May and June) for at least three consecutive years. Biologicals (stem weevil, bud weevil and stem gall fly) are also commercially available to combat CaT. Spot chemical applications can be done, but care must be taken so other plants, like alfalfa and clover, are not killed, too.

Leafy spurge (LS) is now found across much of the northern U.S. where it has been displacing native plants in non-croplands, grasslands and savannas of the Great Plains. A native to Europe and Asia, LS is tolerant of a wide range of habitats, from dry to moist, sunny to semi-shade. It is very aggressive in dry, poor soil conditions where there is less competition from native plants.

A perennial that grows 2-3.5 feet tall, LS has yellow-green, umbrella-shaped flowers that bloom from June into the fall. The plant has a deep vertical root and extensive root system and can spread quickly. Seed capsules "explode" seeds up to 15 feet away with the seeds remaining viable in the soil for seven years.

There are several ways to control or eradicate LS — by prescribed burning, with chemical applications, or by using biologicals (root-boring beetles, root-mining beetles, and midge). You can also use goats to graze LS areas with LS as they that will eat it.

Spotted knapweed (SK) came from Europe and Asia and has become a serious problem in pastures and rangelands of western states. A biennial that grows 2-3 feet tall, SK has wiry stem, small, grayish leaves, and thistle-like, pink or purple flowers that bloom from July through September. The seeds remain viable in the soil for seven years.

Although it is not yet widespread in Carlton County, SK is starting to spread more rapidly in local gravel pits, overgrazed pastures, along roads, and on outer areas of agricultural fields. According to Salzer, SK seeds came to Carlton County farms through hay transported from western states during the 1988 Minnesota drought.

SK can spread through moving of gravel or hay from infested pits or fields. In addition, another way SK and other invasive weeds are spread is "via roadside mowing and graveling," said Smith, as well as by moving farm and recreational equipment that pick up seeds from fields and inadvertently drop them in other areas. "Cleaning of equipment before moving is needed to prevent this."

Early detection and pulling plants are the best ways to eradicate SK. Mowing may help if done before the plants go to seed. Chemical applications must be done with great caution as they also kill native plants. According to Salzer, a Moose Lake area farmer has worked with several different non-chemical ways to control SK. Mob grazing can work as well as biologicals (root-boring weevils, seedhead weevils, and seedhead flies), but it takes both of them to have a real impact.

Purple loosestrife (PL) is not something found on crop or hay land as it is a wetland plant. However, it invades not only lakes and rivers, but also marshes, wetlands, roads, canals and drainage ditches that border many hay and croplands. Introduced into the eastern part of North America in the 1800s, this invasive weed is now in 40 states.

PL is a beautiful, tall (2-7 feet high) plant with pretty pinkish-purple flowers on the top of each "flower spike." Once distributed as an ornamental plant, the seeds were carried by winds from gardens and nurseries into wetlands, lakes and rivers where they easily spread to other areas by moving water and wetland animals. Each mature plant can produce over two million seeds each year! No wonder there are currently about 2,000 PL infestations recorded in 77 of Minnesota's 87 counties, including in Carlton County.

As it invades marshes and lakeshores, PL replaces cattails and other wetlands plants that are used as food, shelter and nesting sites for song birds, fish and native wetland animals, such as ducks, geese, muskrats, frogs, toads, and turtles. In heavy PL-infested areas, many rare and endangered wetlands plants and animals are at great risk.

As PL can still be found in single seed and seed mix packages, it is important to read labels and not buy those packages. For small infestations in easy to access areas, it is best to manually pull out the plants in June, July and early August when the plants flower and are recognizable but before they go to seed. Remove as much of the root system as possible and dry the plants well away from water. Burning the plants is best as composting may not destroy the seeds. There are biologicals (leaf eating beetles) that can be used on small infestations. Herbicides can also be used, but a MNDNR permit is needed.  

All of this information brings up a contentious issue. Since many of these invasive weeds are found along roadsides, and since Minnesota law says that these invasive and noxious weeds must be eradicated or controlled, whose job is it to control them along the road? The landowner who technically owns the land? Or the government who owns the right of way where most of these weeds grow and spread unchecked? No matter the answer, I encourage landowners and local governments to work together to do as much as they can — together — to control and reduce the spread of these invasive weeds!

I also encourage everyone to check your own property for invasive weeds and to do something about them. If you aren't sure a plant is an invasive weed, pull it up and bring it to your local SWCD, Extension, DNR, or NRCS office and have them identify it and, if it is, how best to control it.

Doing nothing about these weeds on your property is actually doing something — it's allowing them to spread to other parts of your property and neighboring properties.

I, along with other landowners, request that you please don't share your weeds! As Smith so aptly stated, "When it comes to weeds, if you don't take care of your problem, it becomes your neighbor's problem as well!"


Kim Samuelson is Carlton SWCD's elected supervisor for District 4. For more information, call 218-384-3891, visit, find them on Facebook page (Carlton SWCD), or stop by their office at 808 Third St., Carlton.