New pasture weed

Asked May 25, 2020, 9:31 AM EDT

Need help identifying

Washtenaw County Michigan

4 Responses

More information is needed. How tall is the plant? What do the leaves and roots look like? Have any buds opened into flowers and if so what color? Where does it grow?

My best guess based on these photos is some kind of dock, but that could be wrong. If you can send some more information it could help.

Regards,
Kim Cassida
cassida@msu.edu

Hi Kim, the plant has grown almost 14 inches high before we cut the pasture. If it’s the same weed I saw last year it had yellow flowers. I believe I asked this question last year but I don’t know how to research things that I’ve already asked. It’s hard to spot it first when the grass is going to seed but you notice it when the horses eat around it?

Anything else I can do?

The weed in your photo is called red sorrel or sheep sorrel. It may not be the same weed as last year because this one does not have obvious yellow flowers. It has inconspicuous greenish or red flowers. This weed is typically found in places where fertility is poor so that more desirable species cannot compete. It is not palatable as you have observed, so overgrazing will also give it an competitive advantage. It is a perennial that spreads by underground stems and also has seeds that live in soil for 25 years. Mowing will not kill it. Herbicides could be effective but herbicide application will need repeating because this will keep coming back from seeds unless you correct the underlying problem. While it is not palatable, this weed can be toxic to horses if they eat a large amount of seeds in a short time (not very likely). Your best bet for control is to correct any soil pH or fertility deficiencies in the field and reduce the grazing pressure so desirable plants can compete. Overseeding with better grasses may help, but soil deficiencies need to be addressed first. If you visit www.forage.msu.edu/extension, you can find many resources to assist. Look under the "Soil fertility," "Establishment" and "Horses" sections and let me know if you have more questions.

Regards,
Kim Cassida
cassida@msu.edu