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Broadleaf Weed · Perennial · Mistaken for Clover

Yellow Oxalis (Wood Sorrel) Control Guide

Oxalis stricta

Yellow oxalis throws its seed. UW-Madison Extension says ripe pods launch seed 8 to 10 feet, and UMD Extension says as far as 12 feet. A 12-foot throw covers a circle of about 450 sq ft around one plant. It also looks like clover at a glance, so people spray it at the wrong time for the wrong reason. Identify it, then treat or pull it before the capsules ripen.

Yellow oxalis (Oxalis stricta) invading a tall fescue lawn with bright yellow five-petaled flowers visible among three-leaflet plants
Yellow oxalis spreading through residential tall fescue, bright yellow flowers among clover-like three-leaflet plants.
Anton Schwarz, Resident Lawn Types Expert

★ Author

Anton Schwarz, Resident Lawn Types Expert

"August 22nd, 2024, I walked a tall fescue lawn in Naperville where the homeowner had been spraying Weed B Gon Original three times per summer for two years targeting what he called 'clover patches.' The patches were yellow oxalis, heart-shaped leaflets with notched tips, bright yellow flowers in among the leaves. He'd been treating it as clover, spraying in July and August heat after the pods had already fired their seed across the yard. We switched to SpeedZone, whose label lists yellow woodsorrel, sprayed on October 8th in cool weather, and started pulling seedlings the next spring before they set pods. By spring 2025, most of the oxalis was gone. The timing depends on knowing what you're spraying."

Quick Stats

Control difficulty:
Moderate
Primary control:
Broadleaf herbicide listing yellow woodsorrel (triclopyr, fluroxypyr, 2,4-D or dicamba products) while plants are actively growing
Secondary control:
Hand-pulling small infestations; pre-emergent in beds and thin edges to stop seedlings
Time to control:
Repeat treatments as new seedlings emerge; seed capsules form late spring to early fall (Penn State)
Seed throw:
Seeds ejected 8-10 feet (UW Extension) and up to 12 feet (UMD Extension)

How to Identify Yellow Oxalis

Macro close-up of yellow oxalis showing three heart-shaped leaflets with notched V-shaped tips and a bright yellow five-petaled flower
Yellow oxalis field ID: three heart-shaped leaflets with notched tips, the most reliable marker against clover, which has oval leaflets without a notch.

Yellow oxalis has three signature features that separate it from clover and other look-alikes:

  • Three heart-shaped leaflets with a notched tip, growing from a central stalk. Clover leaflets are oval and never notched.
  • Small bright yellow five-petaled flowers. UMD Extension puts flowering from May through September. Clover flowers are white or pink globular heads.
  • Upright seed capsules that look like miniature okra. When ripe they split and eject seed, 8 to 10 feet per UW-Madison Extension and as far as 12 feet per UMD Extension.

Growth pattern: Penn State classifies yellow woodsorrel as both an annual and a perennial, with taproots and rhizomes that can produce new plants at nodes. It produces flowers, capsules and seed from late spring to early fall. UW-Madison calls it one of the latest germinating annual weeds.

The Number That Decides: How Far One Plant Seeds

The two extension figures give a range. A seed thrown 8 feet in every direction covers about 200 sq ft. At 10 feet it is about 315 sq ft. At UMD's 12 feet it is about 450 sq ft, nearly half of a 1,000 sq ft lawn section from a single plant. That is our arithmetic on the published distances (area of a circle).

So the job is to remove plants before capsules ripen, not after. Penn State says pre-emergents such as prodiamine, pendimethalin, dithiopyr and isoxaben prevent seedlings but do not affect established plants from rhizomes. A pre-emergent protects beds and thin edges from the seed rain. It does not replace pulling or spraying the parents. Miss one flowering plant in July and next spring's seedlings can cover a 450 sq ft circle around where it stood.

What Actually Kills It: Where the Sources Agree and Disagree

The extension sources do not agree on how easy oxalis is to kill with herbicide, and we are not going to paper over that.

  • Penn State Extension lists postemergence herbicides containing triclopyr, fluroxypyr, 2,4-D and dicamba as effective.
  • Clemson HGIC rates 2,4-D + dicamba + MCPP as good control in bermuda, zoysia and tall fescue, triclopyr as fair to good in zoysia and tall fescue, and atrazine as fair to good in St. Augustine and centipede.
  • UW-Madison Extension says most herbicides are not very effective on Oxalis and that hand weeding and mulching work best.

You may have read that three-way mixes give only 30-50% knockdown on oxalis and that four-way mixes outperform them. We could not find a source for either figure. What decides the product is the label: it must list yellow woodsorrel and your grass.

  • SpeedZone EW (PBI-Gordon): carfentrazone + 2,4-D + MCPP + dicamba. The label lists oxalis (yellow and creeping woodsorrel). Not for St. Augustine, centipede, bahia, seashore paspalum or carpetgrass.
  • Ortho Weed B Gon Chickweed, Clover & Oxalis Killer for Lawns Concentrate: 8% triclopyr. 1 fl oz per gallon of water per 200 sq ft. Not for bahia, bermuda, centipede, kikuyu or St. Augustine lawns.
  • Turflon Ester Ultra (triclopyr): labeled for tall fescue, perennial ryegrass and bluegrass lawns. Useful for spot-treating established patches in those grasses.

When to Spray

  1. While actively growing. UMD Extension's timing rule.
  2. Before seed set. Capsules form from late spring to early fall (Penn State), so young spring plants are the priority.
  3. Out of the heat. Clemson says spray below 90°F. The SpeedZone EW label warns against applying above 90°F unless temporary turf injury is acceptable.

A fall application in cool weather is a good follow-up for plants that escaped. In St. Augustine or centipede lawns, check the grass list first: both SpeedZone EW and the Ortho triclopyr product exclude them.

Why Yellow Oxalis Keeps Coming Back

  • Plants left to set seed. Each missed plant can reseed a circle up to about 450 sq ft.
  • No barrier where seed lands. Beds and thin lawn edges without a pre-emergent or mulch catch the seed. Clemson notes the seeds need light to germinate.
  • New introductions. Oxalis arrives in nursery containers, mulch and topsoil. Inspect plants before planting them.

Penn State says improving turf density through fertilization, regular mowing and well-adapted grasses reduces infestations. Keep tall fescue or Kentucky bluegrass dense so seed has less bare soil to land on.

Frequently Asked Questions

How is yellow oxalis different from clover?

Three differences. (1) Leaf shape: oxalis leaflets are heart-shaped with a notched tip; clover leaflets are oval or egg-shaped with no notch. (2) Flowers: oxalis has small bright yellow five-petaled flowers; white clover has white globular flower heads. (3) Seed pods: oxalis forms upright, okra-like capsules that burst. They are not related. Clover is a legume (Fabaceae); oxalis is in Oxalidaceae.

Does 2,4-D work on oxalis?

The sources disagree on how well. Penn State Extension lists herbicides containing triclopyr, fluroxypyr, 2,4-D and dicamba as effective postemergence options. Clemson HGIC rates 2,4-D + dicamba + MCPP as good control on bermuda, zoysia and tall fescue, and triclopyr as fair to good on zoysia and tall fescue. UW-Madison Extension says most herbicides are not very effective on Oxalis and recommends hand weeding and mulching. We have not found a published knockdown percentage for any of these, so we do not quote one. Pick a product whose label lists yellow woodsorrel and is labeled for your grass.

When is the best time to spray oxalis?

When it is actively growing, per UMD Extension, and before seed capsules ripen. Penn State says it produces flowers, capsules and seed from late spring to early fall, so a spring spray on young plants removes them before they throw seed. Fall sprays in cool weather are a good follow-up. Avoid heat: Clemson says spray below 90°F, and the SpeedZone EW label warns against applying above 90°F unless temporary turf injury is acceptable.

My oxalis came from new sod or mulch. How do I prevent it?

Seed is the main problem. UMD Extension says ripe capsules eject seeds as far as 12 feet. Penn State lists dithiopyr, pendimethalin, prodiamine and isoxaben as pre-emergents that prevent seedling emergence, but they do not affect established plants from rhizomes. The Barricade 4FL label lists yellow woodsorrel from seed. Clemson notes seeds need light to germinate, so a light mulch layer in beds helps. The sources we checked do not state how long oxalis seed survives in soil.

Is yellow oxalis the same as red oxalis or purple oxalis?

Different species, same genus. Yellow woodsorrel (Oxalis stricta) and creeping woodsorrel (Oxalis corniculata) are the common lawn weeds with yellow flowers. The SpeedZone EW label lists both. Purple-leaved oxalis sold for gardens (such as Oxalis triangularis) is usually planted on purpose.

Will pulling oxalis kill it?

Often, if you catch it early. UW-Madison Extension says common yellow woodsorrel pulls up quite easily and does not resprout from roots left behind. Penn State notes the plant can have rhizomes that produce new plants at nodes, so check for runners. UMD says hand pulling works best at the start of an infestation, on young weeds, in moist soil. Pull before the capsules ripen, and bag the plants.

Is yellow oxalis edible like clover?

Oxalis leaves are sour from oxalic acid, the same compound in spinach and rhubarb, and are sometimes eaten in small amounts. Do not eat plants from a treated lawn. After herbicide treatment, follow the label re-entry instruction. The SpeedZone EW label, for example, says not to enter treated areas until the spray has dried.

My lawn has oxalis everywhere from years of neglect. What is the realistic plan?

Treat in spring before seed set with a product whose label lists yellow woodsorrel and your grass, follow up in fall, and pull or spot-treat new seedlings. Thicken the turf with fertilization and overseeding, which Penn State says reduces infestations. Use a pre-emergent in beds and thin edges to stop seedlings. We have not found published reduction percentages for this kind of program, so we do not promise one.

Related Resources

Sources