One of the signs that spring has arrived is when the yellow flowers of buttercup begin to appear, but it's during the winter months that the vegetative growth of buttercup takes place. As a cool season weed, this plant often flourishes in over grazed pasture fields with poor stands of desirable forages. In fact, many fields that have dense buttercup populations are fields heavily grazed by animals during the fall through the early spring months.
Buttercup can sometimes be classified as short-lived perennials, but often grow as winter annuals. Plants typically produce five, shiny yellow petals in the early spring. There are four different species of buttercups that may be found in Kentucky: bulbous buttercup, creeping buttercup, tall buttercup, and small flower buttercup. Although each of these plants may have somewhat similar flower heads, each of these buttercup species differs somewhat in their vegetative leaf characteristics. New seed are produced during the time petals are showy. Waiting until after flowers appear can be too late to implement control tactics. This is one reason buttercups can survive year to year and new plants emerge each year.
Most buttercup plants emerge from seed during the fall or late winter months. Therefore, pasture management practices that improve and promote growth of desirable plants during these months is one of the best methods to help compete against the emergence and growth of this plant. Whereas, livestock animals allowed to overgraze fields during the fall and winter months is one of the main factors that contribute to buttercup problems. Mowing fields or clipping plants close to the ground in the early spring before buttercup plants can produce flowers may help reduce the amount of new seed produced, but mowing alone will not totally eliminate seed production.
For chemical control, herbicides registered for use on grass pastures that contain 2,4-D will effectively control buttercup. Depending on other weeds present products that contain dicamba+2,4-D, or metsulfuron can also be used. However, legumes such as clovers interseeded with grass pastures can be severely injured or killed by these herbicide products.
For optimum results apply a herbicide in the early spring (February - March) before flowers are observed, when buttercup plants are still small and actively growing. For best herbicide activity wait until daytime air temperatures is greater than 50 F for two to three consecutive days. Consult the herbicide label for further information on grazing restrictions, precautions, or other possible limitations.
For fields heavily infested with buttercup a variety of control tactics may be needed. Apply a herbicide to help reduce the population of buttercup plants in the spring plus use good pasture management techniques throughout the year to help improve and thicken the stand of desirable forages.
Worldwide, there are approximately 600 species of Ranunculus, commonly known as buttercup or crowfoot. Fresh Ranunculus leaves, flowers, and stems have a sharp, pungent taste and are usually avoided by grazing livestock. Some Ranunculus species contain varying quantities of ranunculin, a compound hydrolyzed to protoanemonin when plants are damaged - for example, by grazing or mowing. Protoanemonin is a vesicant, causing blistering of the skin, mouth, and digestive system on contact. Ranunculus species with high ranunculin concentrations are the most toxic. Dried Ranunculus is expected to lose toxic potential fairly rapidly, although specific research has not been published to confirm this. Protoanemonin forms a non-vesicant compound, anemonin, upon drying.
Buttercup ingestion can cause mouth pain, blisters, drooling, oral and gastric ulcers, colic, and diarrhea. Clinical signs can be severe if large quantities of buttercup are ingested, but the acrid taste usually deters further grazing in horses and cattle. Clinical signs are typically seen only when other forage is unavailable and animals are forced to consume buttercup. Sheep may be more likely than other grazing animals to eat the plants, particularly immature stages. Horses are probably the most sensitive species to the gastrointestinal effects of buttercup.
A review of UKVDL records over the last 13 years found no cases of livestock deaths attributable to buttercup ingestion. It is possible that cases of colic or diarrhea have been caused by buttercup ingestion but were never attributed to the plant. Because animals will try to avoid grazing buttercup when possible, it proliferates in overgrazed pastures. Overgrazing is prevented by maintaining appropriate stocking rates. Buttercup poisoning is most likely in starving animals. The risk in Kentucky is minimal as long as plenty of other forage is available; unpalatable fresh plants are generally avoided when possible, and dried plants are less toxic than fresh.
For more information contact the Pulaski County Extension office. Information gathered form Dr. JD Green and Dr. Megan Romano with the University of Kentucky.