Terrestrial invasive species

Nature

Most of these invasive plant factsheets are created from the booklet Minnesota invasive non-native terrestrial plants, an identification guide for resource managers.

Check the additional resources and herbicides table for more information.

White and yellow sweet clover (Melitotus alba, M. officinalis)



Description:

Appearance: Biennial herbaceous plants, they are very similar. Yellow sweet clover is usually shorter and blooms earlier. First year plants do not bloom. Second year plants grow 3 - 5' high and are bush-like. Sweet clovers are very fragrant.

Leaves: Alternate, divided into three finely toothed leaflets, middle leaflet grows on a short stalk.

Flowers: Crowded densely at the top four inches along a central stem, each flower is attached by a minute stalk; bloom June through August on second year plants.

Seeds: One or two hard small seeds per flower; they stay viable in the soil for 30 years.

Roots: Strong taproot.

The key to controlling sweet clovers is to halt the flowering stage and then concentrate on depleting viable seeds in the soil. Be aware that too frequent measures can also hurt native plants.

Ecological Threat:

  • Sweet clover invades and degrades native grasslands by overtopping and shading native sun-loving plants thereby reducing diversity. It grows abundantly on disturbed lands, roadsides and abandoned fields.
  • It responds favorable to prescribed burns by scarifying seeds thereby stimulating germination. First year plants are hard to detect.
  • Native to Europe it was brought to the U.S. in the late 1600s and still used today as a forage crop and soil enhancer predominantly in the Great Plains and Upper Midwest.

Control Methods:

Mechanical

Prescribed burning, a hot early complete first year burn followed by a hot late spring second year burn, (repeat after two years)

Hand pulling, effective on small infestations when the soil is moist

Cutting, before flowers emerge

Chemical

Spray emergent seedlings with 2,4-D amine or mecamine after a fall burn, or after a spring burn before native vegetation emerges

 


Native Substitutes:

Additional Resources