Noxious Weeds
Sericea lespedeza
Sericea lespedeza, or Lespedeza cuneata, is an introduced, perennial legume, sometimes also referred to as Chinese bush-clover. It was first planted in the US by the USDA in 1900 for erosion control and has since been deemed a noxious weed. Sericea is a nitrogen-fixing plant that is found in places where other plants may have trouble surviving. It is both drought- and flood-tolerant, prefers full sun but can survive in partial shade, and persists in a wide range of climates and habitats. The best way to control it is by identifying it early and managing appropriately.
Sericea lespedeza is a woody plant, light to medium green in color, that grows 2-6 feet in height. Its leaves are in groups of 3, each leaflet wider at the tip than at the base, with a distinctive point at the tip. Leaflets are small, only about ½ - 1 inch long, and only up to ¼ inch wide. Flowers bloom from July-October and are pea-like, typically white with purple interiors grouped 1-4 per stem. With practice, Sericea lespedeza can become easy to pick out from afar as it typically grows in large patches.
The easiest way to control this weed is to identify it early on and just spot spray it with the appropriate chemicals. Due to the plant’s extensive seed bank, the same areas will likely require treatment for many years and should be monitored regularly.
If not caught early and Sericea lespedeza has spread throughout a field, one of the most effective ways to treat it is a summer burn followed by intensive spot spraying. Burn the field between July 16th and October 1st to kill all of the living Sericea. This will force it to use up its root nutrients and put all of its energy into new growth. It might seem like the fire didn’t work, but this will allow for maximum contact of your herbicide. Return about 3-4 weeks after this fire to spot spray, and then come back every 3-4 weeks after that to spray anything that may have been missed. Again, these areas should be monitored to ensure termination.
Musk Thistle
Musk thistle, or Carduus nutans, is an exotic, biennial plant that was originally introduced from Europe in the mid-1850s as a garden plant. They can survive in a variety of environments and are found primarily throughout the eastern two-thirds of Kansas. As a biennial, the plant will establish itself as a rosette, or a cluster of leaves in a circle, low to the ground, in its first year. (See photo below) During its second year, it will bolt, or flower. The best way to control them is to get rid of them during their rosette stage before they flower. Musk thistle has been declared a noxious weed throughout the state.
Musk thistles are spiny-stemmed and can grow up to 9 feet in height. The stems stick straight up and are covered in spiny wings. Their leaves are spiny, deeply serrated, and can grow up to 20 inches long. Flowers bloom from May-August, are bright pink in color, and can grow up to 3 inches in diameter.
Again, musk thistle is the easiest to control when it is in the rosette state, before bolting. They can be sprayed or dug up at this point and disposed of. However, if the plant has gone to flower, they must be removed and burned. The root should be cut 2 inches below the surface and all parts of the plant destroyed.
Please Note: Not all thistles are bad! There are several native Kansas thistles that are beneficial to wildlife, pollinators, and soil health. These will all be white or very light green on the underside of their leaves.
Field Bindweed
Field bindweed, or Convolvulus arvensis, is a perennial, vining plant that originated in Eurasia and was brought to the United States as an ornamental and medicinal herb. It is found throughout Kansas and has been declared a noxious weed because of its invasive nature.
Bindweeds are vines that typically grow along the ground and will climb up any nearby plants that they come into contact with. Bindweed often encroaches into fields from roadsides and can form a dense mat of vines and leaves. The leaves are typically rounded triangular shapes and can grow up to 4 inches long. Flowers are white, sometimes pale pink and are trumpet-shaped, similar to morning glories.
Bindweed control is difficult as its roots extend deep into the soil and seeds can remain viable for up to 50 years. Herbicides applied when the plant is flowering can be effective in killing bindweed but should be used with caution as most will also kill any native forbs in the area. If only a small amount is present, commit the time to pulling the weeds out when they regrow - continuous pulling during the growing season should eventually exhaust the roots of the plant and eradicate it.
Johnsongrass
Johnsongrass, or Sorghum halepense, is a perennial grass from the sorghum family. It is native to the Mediterranean region and was introduced to the United States in the 1830s as a forage crop. It is found throughout Kansas and thrives in wet and disturbed soils.
Johnsongrass is a sod-forming grass and is typically very tall - up to 7 feet in height at maturity. Its blades are usually hairless, often purple spotted, and can get up to 3 feet long and ½ to 1½ inches wide. When young, there will often be one purple blade in each plant. The heads are purplish in color with whorled branches, blooming from July-October, and in a pyramid shape overall. It reproduces by seed and rhizomes, or underground stems.
Like all noxious weeds, the easiest time to control johnsongrass is before it has spread throughout a field. If only a small area infested, pull up the plants individually when the soil is soft after a rain. Broken stems and roots should be removed to the fullest extent possible. For a larger infestation, an herbicide application when the plant is about 18” tall can kill these young living plants and often the rhizomes that are developing below the surface. Individual plants can and should be pulled if they reemerge.
Eastern Redcedar
Eastern redcedar, or Juniperus virginiana, is a coniferous tree species found throughout Kansas. Redcedars are able to survive in a wide array of habitat types, withstanding extreme drought, heat, and cold. Often planted as shelterbelts and windbreaks, some landowners consider cedar trees a valuable species, however, when introduced to native prairie landscapes they can quickly take over and degrade habitat quality.
Eastern redcedars are capable of growing up to 90 feet, but typically are around 30-40 feet at maturity. Their bark is red-brown and splits into long, scrappy strips. Leaves are oppositely branched, scale-like, and usually green but sometimes slightly blue-green. Pollen sheds from March to May and fruits develop from August to September.
In areas where complete elimination is desired, such as tallgrass prairie or pasture, staying on top of the management will ensure that the infestation is being properly dealt with. It is often recommended to go after the “women & children first” when dealing with redcedars. Eliminating female trees will be the easiest way to prevent new growth, and younger trees are the easiest to kill. Female trees can be identified by the small, grey-blue, berry-like cones they produce in spring, and the green flowers that appear in late winter. Male trees will produce brown cones and their flowers will be yellow. Small trees can easily be controlled by prescribed burning. It is recommended that burning to control woody invasion take place in February-March, or in late July-August. Larger trees will need to be controlled via cutting and spraying or felling trees completely. In other areas, such as those bordering timber stands, or those that are being managed for wildlife, it may be beneficial to leave some downed trees along field borders to create a ‘feathered edge.’
Notes on herbicides
Pay attention the type of herbicide you use, as some may also affect desirable grasses and forbs.
ALWAYS read herbicide label instructions carefully and follow any guidance for use of the chemical and appropriate personal protective equipment closely!
For recommendations on specific herbicides, please contact a biologist, or consider consulting the K-State Chemical Weed Control booklet, available online, through their bookstore, and linked below.