Clover-Like Weeds With Yellow Flowers: Black Medic, Hop Clover or Woodsorrel?

Updated November 2, 2026

If your lawn has small, low, clover-like weeds with yellow flowers, it is almost always one of three plants: black medic, hop clover or yellow woodsorrel. Penn State Extension groups black medic and yellow woodsorrel with white clover as the three-leaflet look-alikes most often found in lawns, and Michigan State University Extension lists hop clover and the woodsorrels as the weeds most like black medic (Penn State Extension; Michigan State University Extension). Here’s how to tell them apart, why they move in, and what works on each.

Black medic vs hop clover vs woodsorrel: how to tell them apart

• Woodsorrel is the odd one out. Its flowers are single and “distinctly 5-petaled, open”, and its leaflets “lack a pointed tip, and all 3 are attached directly to the petiole” (University of Maryland Extension). UC IPM adds that oxalis leaves “lack a stipule and generally have a more pronounced indentation at the top of each leaflet” (UC IPM). Full details are on our oxalis (woodsorrel) guide.
• Black medic and hop clover both make little round yellow heads. Michigan State says hop clover has similar habits, foliage and yellow flowers, “but the leaves and flowers are larger than black medic”. The surest check is an old flower head: hop clover’s petals stay on and turn brown, while black medic’s “drop off, revealing a cluster of pods that turn black at maturity” (Michigan State University Extension).
• Black medic’s other clues: each leaflet ends in a “short but distinct point”, the stems trail but “do not root as they creep”, and seeds sit in a “kidney-shaped black pod” (University of Maryland Extension).
• Small hop clover (Trifolium dubium, also called lesser trefoil) is a close relative: an annual with tiny yellow flowers, 3 to 15 per head, from late spring to early fall, and it “handles foot traffic and mowing well” (NC State Extension). NC State notes that the hop clovers look alike and respond similarly to herbicides (NC State Extension).
• The common names overlap. NC State’s Plant Toolbox lists “hop clover” and “yellow trefoil” among the common names for black medic itself (NC State Extension), so check the flowers and pods rather than the name.

About this table: Features from Penn State Extension, University of Maryland Extension, NC State Extension, NC State Extension and the Michigan State University Extension weed ID guide (pp. 112–114 and 145). Black medic and hop clover are both legumes; UC IPM counts black medic among the “annual clovers” (UC IPM).

How to get rid of black medic, hop clover and woodsorrel

Start with the lawn. Penn State says improving turf density reduces all three look-alikes (Penn State Extension). NC State: “A dense, vigorous turf is the best way to reduce the encroachment of winter annual weeds.” University of Maryland Extension’s list: fertilize as recommended for the season and grass type, mow high, overseed cool-season lawns each fall, and core-aerate compacted soil (University of Maryland Extension).

• Pull or dig small patches. For black medic, remove the whole plant “including the central root system”, by hand or with a weeding tool; moist soil makes it easier (University of Maryland Extension). Woodsorrel is “easy to pull from the lawn, especially when the soil is moist” (Penn State Extension). UC IPM says annual clovers can be hand-pulled before seeds form, repeated as new seedlings come up (UC IPM).
• Expect a few seasons. Clover seed has a hard coat, and UC IPM says “clover seeds can germinate over many years, making the control of these plants an ongoing effort” (UC IPM).
• In flower beds: annual clovers are easily controlled by hand-pulling, hoeing or cultivation, and a 4-inch layer of organic mulch put down before the seeds germinate can keep them from establishing (UC IPM). See also how to prevent weeds in flower beds.

Weed killers for black medic and yellow clover in lawns

• Spot-treat with a lawn broadleaf herbicide while the weeds are actively growing. For black medic, University of Maryland Extension says to look for one or more of these active ingredients: 2,4-D, MCPP (mecoprop), dicamba or triclopyr (University of Maryland Extension).
• 2,4-D alone won’t do it. UC IPM: “The herbicide 2,4-D is not effective for clover control; it will injure the plant but does not control it.” So pick a product labeled for clover, usually a mix that includes mecoprop or dicamba (UC IPM).
• Match the product to your grass. UC IPM says warm-season grasses such as bermudagrass, zoysiagrass and kikuyugrass tolerate mecoprop and dicamba but not triclopyr, while cool-season grasses tolerate all of the clover herbicides (UC IPM). Clemson’s table for warm-season lawns lists black medic among the weeds controlled by 2,4-D + dicamba + quinclorac products on bermudagrass and zoysiagrass (Clemson HGIC). Clemson: “Read the product label to be sure the herbicide is labelled for use on the specific turfgrass in the lawn!”
• Protect trees and shrubs. “Do not spray herbicides containing dicamba over the root zone of desirable trees and shrubs.” Check local pesticide rules before you buy (University of Maryland Extension).
• Woodsorrel is not a clover (Penn State); for its control options see the control section of our oxalis guide. For white clover, see the clover guide.
• Use only products labeled for lawns and for your grass type, as the label directs.

When to treat clover-like weeds with yellow flowers

The quick fix Clemson recommends: treat young weeds in spring or fall on a mild day. Clemson: “Most broadleaf weeds are best treated in the spring or fall when air temperatures are between 65 and 85° F.” “Best results occur when weeds are young.” (Clemson HGIC)

• Hop clover sprouts now. NC State says winter annual broadleaf weeds such as hop clover “germinate in the fall or winter”, grow during warm spells, set seed in spring and die as temperatures rise in late spring and early summer (NC State Extension).
• Black medic mostly sprouts in spring. It is typically a summer annual that germinates in spring and blooms in summer, though some plants germinate in autumn (University of Maryland Extension).
• Small is easier. UC IPM says that once annual clovers reach 3 to 4 inches tall, “control with herbicides is more difficult” (UC IPM). UC IPM also says clovers begin to germinate in fall when soil temperatures are in the 50s °F, written for California conditions.
• For fall spray timing and cut-off temperatures where you live, see fall lawn weed control; for local frost dates, see frost dates by ZIP and state or enter your ZIP in the planner.

More weed guides

White clover Oxalis (woodsorrel) Fall lawn weed control Wild garlic vs wild onion Henbit Weed identification guide

Organic options Growing without synthetic sprays? See our organic gardening guides: pest control and fertilizer.