Brad Johnson: Buttercups pretty, but harmful
As you drive around the county, you should notice that farmers and livestock producers are definitely moving at full speed. The corn crop is essentially planted, small grain silage and hay have been made, first crop tomatoes have been set, locally grown produce is being marketed, soybeans are being planted and grass hay has been or hopefully is in the process of being made.
Not to mention livestock producers are weaning fall-born calves as they reach roughly seven months of age, plus, hopefully producers are pregnancy checking cows and conducting other routine, but very necessary herd management.
Whether they’re just a dot here and there or a carpet spread across a pasture or lawn, a familiar sight every spring is the yellow-flowered weed buttercup. There are several different species of buttercup, including tall buttercup, creeping buttercup (low-growing and spreads by stolons), hairy buttercup, and bulbous buttercup. The two most common species of buttercup found in the Piedmont are hairy buttercup and bulbous buttercup.
Bulbous buttercup is a perennial, while an extensive literature search results in information that hairy buttercup may be a winter annual, biennial, or a perennial.
Hairy buttercup is a hairy plant with erect, hairy stems (single or branching from the base) and a fibrous root system. Vegetative characteristics of hairy buttercup are similar to those of bulbous buttercup, except for the bulb-like swelling at the base of the stem of bulbous buttercup. Leaves are dark green with light patches and are divided into three toothed leaflets and flowers usually have five glossy, bright yellow petals.
Winter annual broadleaf weeds (like buttercup) germinate in the fall or winter and grow during any warm weather. Growth may occur in the winter, but the seedlings remain somewhat dormant during the winter. They resume growth and produce seed in the spring and die as temperatures increase in late spring and early summer. Bloom time may range from March through June. They quickly invade thin turf areas, especially where there is good soil moisture.
Fresh buttercup plants are toxic to grazing animals, which can suffer from salivation, skin irritation, blisters, abdominal distress, inflammation and diarrhea. Fortunately, buttercup has a strong, bitter taste, so animals generally try to avoid it if more palatable forage is available. Also, the toxin, protoanemonin is not very stable and loses its potency when dry, so buttercup is generally not toxic in hay.
For best prevention and control of buttercup in lawns and pastures, promote healthy grass by overseeding, fertilizing as needed, and not over-grazing. Adding lime to the soil as needed can improve grass health and keep buttercup from re-establishing. However, lime won’t control buttercup that’s already established. It also helps to improve soil drainage. Reduce compaction by aerating and clean mowers and other equipment to avoid spreading buttercup seeds to un-infested areas.
Homeowners may be able to dig up small infestations of buttercup, but make sure all the runners and roots are removed. Incomplete digging may increase the buttercup population because it can sprout from nodes along the stem and root fragments.
Herbicides can be used if allowed and appropriate for the site and land use. Follow all label directions to ensure safe and effective use.
Herbicides with the active ingredient glyphosate can be applied to actively growing plants before they seed. However, glyphosate is a non-selective herbicide, so make sure it doesn’t get on desired plants and grasses.
Broadleaf herbicides can be applied over grassy areas infested with buttercup, but it’s late enough in the season, I’d be hesitant to apply them now.
Broadleaf herbicides should be applied to buttercup in early and mid-April for best results. Research from NCSU has shown broadleaf herbicides with the active ingredients metsulfuron (excellent), 2,4-D amine (excellent), clopyralid and triclopyr (good), or triclopyr (good) will control buttercup when properly applied.
It will probably take two or three applications to control buttercup because of the seed bank and because some mature plants will generally recover.
Brad Johnson is an agent for the Agriculture-Livestock and Dairy branch of Rowan County Cooperative Extension service. He can be reached at 704-216-8970