by Sally Colby
The sight of horses standing in a field of bright yellow buttercups is attractive, but buttercups in a horse pasture aren’t good. The presence of buttercups, especially an overabundance, signals the need for more proactive pasture management.
“Buttercups tend to go with overgrazed pastures,” said Donna Foulk, Penn State extension educator in equine stewardship. “They’re a perennial plant, so the parent plant comes back year after year. They also produce a lot of seeds.”
Foulk explained when a pasture is overgrazed, as is often the case with horse pastures, the canopy is opened up and provides the perfect environment for buttercup seedlings. “Buttercup seedlings like a lot of sunlight,” she said. “If the pasture is overgrazed and there isn’t a lot of tall, thick grass to prevent those seeds from developing into seedlings and then into adult plants, there will be a lot of buttercups in the pasture. In a pasture with grass that’s about nine to ten inches tall, buttercups won’t even have a chance.”
Horse farms often keep a high density of horses per acre, which perpetuates the problem. Foulk says that buttercups don’t outcompete grasses — what happens is that in an overgrazed pasture where there is no strong grass canopy, bare spots develop and buttercups take over.
Although people might look at a pasture and wonder how it happened, a buttercup invasion doesn’t happen suddenly. “It had been happening slowly,” said Foulk. “There’s a massive amount of weeds and very little grass. Creating a whole farm plan, resting the grasses and having a sacrifice area is ideal. Always make sure pasture plants have leaves left so that the plant continues to grow roots and grow taller and healthier.”
Foulk said many buttercup species thrive in hot, dry weather. “There are many different species, so they can live in different types of environments,” she said. “Some species like hot and dry conditions, some like wet conditions. They start to grow early, so people don’t often realize that they’re there. But as soon as the snow melts, you can see small buttercup plants. They aren’t in flower, so people don’t always realize they’re there. But once they get a foothold, they really take off.”
Pastures with poor fertility are the ideal habitat for buttercup growth. Many horse farms don’t conduct regular soil tests and make appropriate adjustments for pH and nutrients, and that lack of care fosters buttercup growth.
Although some horses might sample them, buttercups aren’t really palatable. The plant contains a toxin, so most horses leave them alone. Horses that are forced to eat buttercups due to lack of more desirable species can develop ulcerations on mucous membranes such as gums and lips, and sometimes down into the esophagus. “Horses have to be very hungry and not have anything else available to eat them,” said Foulk. “But buttercups don’t contain a neurotoxin.”
Foulk recommends some steps for dealing with buttercups, which in turn help with better overall pasture management. “Treat grass as if it’s a crop,” she said. “Think of how to get that grass growing taller and healthier. Most pasture grasses are cool season grasses — orchardgrass, timothy and perennial rye, bluegrass and fescue. Their growth is best in spring and fall. In summer, the growth slows drastically and they don’t have the ability to grow back. A lot of pastures are destroyed in summertime — horse owners should realize that that’s an important time to not overgraze because it reduces the plant’s ability to use its leaves for photosynthesis and survive.”
To manage buttercups, owners should check soil fertility through soil testing and make appropriate amendments. “Soil pH needs to be right,” said Foulk, stressing the importance of managing the pasture for healthy grass. “If plants don’t get enough phosphorus and potassium for healthy grass growth, that’s an issue.”
Although mowing a small pasture may seem like a good idea to reduce the number of flowering heads, Foulk says buttercups have a low-growing habit, and the result of mowing will be weakening the desirable pasture species. “Buttercups flower and produce seeds very low to the ground,” she said. “If you try to mow close enough to get all the flowers off, you’re taking the leaf blade of the grass and the grass won’t be healthy.”
Fortunately, it’s fairly easy (and safe) to kill buttercups in a pasture. “It usually takes several herbicide applications because the seeds will still be there,” said Foulk. “It may take several years to kill all of the plants. After the buttercups are killed, there will be bare spots. Unless you have a plan to make the pasture grasses healthy, something is going to fill that bare spot.”
A combination of 2,4 D and dicamba is one of the most effective treatments for treating buttercup infested pastures. “Always follow all label instructions specifically because different companies and different states have different products that can be used,” said Foulk.
Foulk suggests that in some cases, especially where the weed killer label includes time constraints for reseeding after treatment, it’s better to reseed the pasture and allow the grasses to become established before tackling the weeds. “To do it the other way, there’s a lag between using the herbicide and reseeding,” she said. “You really have to have a plan. If the weeds are killed without changing the conditions that allowed buttercups to grow, buttercups or another weed will return.”
by Sally Colby