Tall buttercup is an introduced perennial forb that is widespread throughout much of North America (Figure 1). It is invasive on irrigated and sub-irrigated pastures, meadows, stream banks, roadsides, and ditches. Tall buttercup forms a toxic substance, protoanemonin, when grazed or damaged. Although the plant is typically avoided by grazing animals, livestock poisoning may occur on overgrazed pastures where more desirable forage is lacking.
Tall buttercup is an herbaceous plant that grows from a stout rootstock. Basal leaves grow directly from the root crown or rhizome and are deeply divided into three to five palmate lobes (Figure 2). Stems are one to three feet tall, erect and hollow, with smaller leaves on upper portions of the stem. Each root crown has from one to several stems that are branched above. Soft hairs are present on both leaves and stems. Flowers typically have five, but may have up to eight rounded petals that are glossy yellow in color and about one-half inch long. The plant blooms from late May to September, depending on temperature and moisture.
Tall buttercup spreads primarily by seed but can also reproduce by rhizomes. Seeds are typically viable for less than two years when located in the top inch of soil but can survive longer when buried deeper.
Integrating various management techniques—prevention along with herbicides, mechanical, manual, biological, and cultural methods—will optimize control of tall buttercup.
Preventing seed spread by livestock and farm equipment will help protect non-infested pastures and meadows. Mowers and other equipment used on infested pastures should be cleaned to prevent movement of tall buttercup seed. Livestock grazing infested pastures should be held for at least three days prior to moving to non-infested grazing areas.
Selective herbicides can provide effective control of tall buttercup. Field trials were established on a hay meadow in western Montana to determine the effectiveness of several herbicides for controlling tall buttercup. Treatments included Milestone® herbicide at 5 and 7 fluid ounces per acre (fl oz/A), MCPA at 64 fl oz/A, and metsulfuron-methyl at 1 ounce of product per acre (oz/A). Herbicides were applied at late bud to bloom growth stage in early summer (June 8), and a second application was made in fall (September 16). Herbicides were applied with a CO2 backpack sprayer in 13.5 gallons of water per acre (Figure 3).
Results of the study showed that Milestone at 5 to 7 fluid ounces per acre provided greater than 95 percent control of tall buttercup one year after treatment when applied in either early summer or fall (Figures 4 and 5). MCPA provided greater than 95 percent control one year following an early summer application; however, control was less than 40 percent when applied in fall. Other field trials conducted in Montana show similar results with Milestone on tall buttercup (Strevey and Mangold 2015). Continued annual application of MCPA is discouraged due to reports of possible resistance to this herbicide within tall buttercup populations.
Mowing prior to seed set may reduce tall buttercup seed production; however, in most irrigated and sub-irrigated pastures, the plant will regrow after mowing and set seed later in the season. Proper timing of mowing is critical to promote growth of desirable plants and impact flowering of tall buttercup. Individual tall buttercup plants can be removed by pulling or digging in spring. The entire root system must be removed to control the plant.
No biological control agents are currently available for tall buttercup. Livestock grazing generally increases tall buttercup density, since livestock avoid the plant.
Disturbance caused by livestock will provide open sites that favor establishment of tall buttercup.
Tall buttercup has low tolerance to dry conditions. Regulating the timing and amount of water applied to an infested site may reduce the competitive ability of tall buttercup. Promoting desirable grasses with supplemental fertilization, as well as managing livestock grazing, may reduce buttercup establishment.
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Celestine Duncan contributed to this article.
Published 2017; Reviewed June, 2019.