How to Get Rid of Oxalis (Yellow Woodsorrel) in Lawns and Garden Beds

You bent down to pull what looked like a bit of clover from the edge of the bed, and the stem snapped in your fingers. Two weeks later there are a dozen more. Those heart-shaped leaves are oxalis, and if you want to get rid of oxalis for good, it pays to know why half-measures fail. The cool, damp weeks of autumn are prime germination weather for it, so now is a good moment to start.

Short answer: to get rid of oxalis (yellow woodsorrel and creeping woodsorrel), stop it setting seed and remove the runners, not just the leaves. In a lawn, spot-spray a broadleaf herbicide containing triclopyr or fluroxypyr while the plants are young, repeat after 3 to 6 weeks, and thicken the turf so seedlings have no bare soil. In beds, hand-weed before the plants are about 6 weeks old, sift out the pink runners, and cover the soil with 2 to 3 inches of mulch, because oxalis seed needs light to germinate.

Why is it so stubborn? A single plant can make more than 5,000 seeds and throw them several feet, according to UC Statewide IPM. Pull the top, leave a stem piece behind, and it simply regrows.

By the end, you’ll be able to tell oxalis from its lookalikes, pick a herbicide that’s safe for your grass, and clear beds without replanting the problem.

How to identify oxalis in a lawn or bed

Before you spray or dig anything, make sure it really is oxalis. Three kinds turn up in lawns and garden beds, and all have leaves divided into three heart-shaped leaflets and small yellow flowers with five petals.

The heart shape is the quickest check. Each leaflet has a notch at the tip, as if someone cut a V into it. Clover and black medic leaflets are rounded or oval, with no notch.

Its behaviour gives it away too. Penn State Extension notes that yellow woodsorrel leaves droop and fold at night and open again in daylight. So walk the lawn early in the morning or on a dull evening: the woodsorrel patches look limp and folded, while the clover stays flat.

Yellow woodsorrel (Oxalis stricta)

Yellow woodsorrel is the upright one, usually 4 to 10 inches tall, per NC State TurfFiles. Leaflets are about 1/4 to 1/2 inch across and light green or reddish-green, and the flowers are 1/4 to 1/2 inch wide.

The part that matters for control is underground. It has a taproot plus slender white to pink rhizomes that make new plants at the nodes. It behaves as an annual in some places and a short-lived perennial in others.

Creeping woodsorrel (Oxalis corniculata)

Creeping woodsorrel hugs the ground and roots wherever its stems touch soil. Its leaves are often purple or bronze, though green forms are common. It’s the one you find in pavement cracks, greenhouse pots and close-mown lawns.

Here’s the surprise: UC IPM reports that creeping woodsorrel survives and sets seed even when mowed as close as 1/4 inch. Mowing lower will not starve it.

Bermuda buttercup (Oxalis pes-caprae)

Bermuda buttercup is a different beast: a bulb-forming oxalis that is a weed in mild-winter areas such as coastal California. Its flowers are much larger, 3/4 to 1 1/2 inches across, on stalks 6 to 12 inches tall.

It spreads mainly by bulbs. UC IPM says each plant makes about a dozen small bulbs a year, each under 1 inch long. Pull the leaves and the bulbs stay behind, which is why it gets its own plan below.

Oxalis vs clover vs black medic: comparison table

Most people first notice oxalis because they think their lawn has suddenly filled up with clover. It’s an easy mix-up, and the fix differs. This table sorts the common three-leaflet weeds with yellow or white flowers. For more yellow-flowered lawn weeds, see weeds with yellow flowers in lawns.

Black medic is the lookalike that fools most people, because it also has small yellow flowers. Look closely at the flower itself: black medic has a tiny round cluster of florets, while woodsorrel has one open flower with five separate petals.

If your plant turns out to be clover, read whether clover in a lawn is worth keeping before you spray.

Why oxalis keeps coming back

If you’ve ever weeded a patch clean and watched it come back within weeks, this is why. After the flowers fade, the plant forms narrow, upright seed capsules, and when they’re ripe they split and fling the seed.

How far? Extension services give different distances: up to 10 feet (UC IPM), up to 12 feet (University of Maryland Extension) and up to 16 feet (NC State Extension). Whichever figure you trust, touching a ripe plant while weeding sprays seed across the bed.

The biology works against you in four ways:

• Huge seed numbers. A single plant can produce up to 5,000 seeds in a year, and fresh seed can germinate at close to 100 percent soon after it drops, according to the University of Florida IFAS review of oxalis biology.
• Fast cycle. UC IPM reports that seedlings can begin flowering in about 4 weeks, so several generations fit into one season.
• Wide germination window. Most seed germinates between 50°F and 84°F (UF/IFAS), with an optimum of 60°F to 80°F (UC IPM). That covers most of spring and autumn in temperate gardens.
• Broken pieces regrow. When you pull creeping woodsorrel, UC IPM notes that the taproot or stolons often snap and stay in the soil, and those pieces grow into new plants.

Now the good news. Oxalis has one weakness you can use: its seed needs light to germinate. Clemson Extension and UF/IFAS both point out that anything that keeps light off the soil surface, such as mulch or dense turf, cuts the number of new seedlings.

How to get rid of oxalis in lawns

In turf you’re mostly dealing with yellow and creeping woodsorrel. Control has three parts, and skipping any one of them is why so many lawns stay infested:

• Kill the plants that are there, roots and runners included.
• Stop new seedlings before they get going.
• Close the gaps so nothing moves back in.

1. Spot-spray with a selective broadleaf herbicide

Plenty of lawn weed killers combine 2,4-D, MCPP and dicamba, and Maryland and Clemson list these for oxalis. But two active ingredients stand out.

Kansas State University names triclopyr and fluroxypyr as the effective ones, and UC IPM calls them “extremely effective” on seedling and established creeping woodsorrel in cool-season lawns. Look for them on the label, often combined with other ingredients.

Your grass type decides which one you can use. UC IPM notes that triclopyr alone is not labelled for warm-season lawns, while fluroxypyr is safer there and still very effective.

Clemson lists other options for southern lawns, including atrazine and sulfentrazone plus quinclorac, and warns that centipedegrass and St. Augustinegrass are sensitive to some formulations. Read the label for your grass before you buy, and follow the label for rates and timing.

Spray when the weed is young and actively growing, and plan for a second pass from the start. UC IPM says a follow-up application 3 to 6 weeks later may be needed for complete control.

Spot treatment uses far less product than a blanket spray and is kinder to the rest of the lawn.

2. Use a pre-emergent where seedlings keep returning

Think of a pre-emergent as a fence, not a cure. It stops seedlings but does nothing to established plants or their rhizomes. For lawns, Penn State lists dithiopyr, pendimethalin, prodiamine and isoxaben.

Clemson notes that most woodsorrel seed germinates in late winter and early spring, so the product has to be down before then.

Timing is tighter than most people think. In a 2013 Weed Technology study, isoxaben, indaziflam and dithiopyr cut yellow woodsorrel fresh weight by 95 percent or more when applied at the cotyledon to one-leaf stage. By the two- to four-leaf stage, only indaziflam still gave strong control.

That trial was run in container nurseries, not lawns. The lesson still carries over: a pre-emergent applied late does little.

For heavy infestations in California landscapes, UC IPM suggests up to three pre-emergent applications a year, in early fall, midwinter and late spring. If you’re reading this in early fall, the first of those windows is the one in front of you.

One caution: do not use a pre-emergent where you plan to seed grass soon. See killing weeds before overseeding for the waiting periods.

3. Thicken the lawn and clean the mower

This is the long-term fix, and it’s the least exciting one. Penn State, Clemson and NC State all say the same thing: dense, well-fed turf mowed at the right height leaves little room for woodsorrel seedlings.

There’s a catch with creeping woodsorrel that’s already established. UC IPM warns that extra fertiliser and water make the woodsorrel grow faster too, so feeding alone will not smother it. Kill the weed first, then use fertility to help the grass fill the gaps.

UC IPM also recommends washing or blowing off the mower after cutting an infested area, because seed and clippings travel on the deck into clean turf. It takes two minutes. Honestly, it’s the step most people skip.

How to get rid of oxalis in garden beds and pots

Beds are a different game. In vegetable plots and flower beds you usually cannot spray a lawn herbicide, so the approach is mechanical first, and timing does most of the work.

1. Weed early. UF/IFAS reports that hand-weeding works best on plants 6 weeks old or younger, before seed capsules form. Once capsules are present, bag the plants rather than composting them.
2. Get the runners out. Loosen the soil with a fork and follow the pink rhizomes or rooting stems. UC IPM advises several weedings, because stem pieces break easily. Moist soil makes this much easier, per the University of Maryland.
3. Mulch 2 to 3 inches deep. UC IPM recommends 2 to 3 inches of organic mulch or fabric to keep light off the seed. Thin mulch lets seedlings through; our guide to stopping weeds growing through mulch covers depth and edges.
4. Solarize bad patches. For heavily infested bare ground, UC IPM suggests soil solarization for at least 4 consecutive weeks in the hottest part of summer. Moist heat helps: 4 hours at 97°F cut creeping woodsorrel germination by 96 percent in UC’s data.
5. Check new plants. Woodsorrel rides in on nursery pots. Pull any seedlings with heart-shaped leaflets out of new pots before you plant them.

For woodsorrel in gravel, paving joints and rock gardens, where there are no crop roots to protect, see killing weeds in rock gardens and gravel beds.

You might be tempted by a kitchen-cupboard fix. Vinegar and other contact sprays scorch the leaves but leave the taproot and runners alive, so expect regrowth; what horticultural vinegar really does explains why.

Controlling Bermuda buttercup

Bermuda buttercup needs patience more than force. For small patches, UC IPM recommends repeatedly removing the whole plant and sifting the soil for bulbs and bulblets. It’s slow work, but every bulb removed is one less plant later.

Glyphosate can be used as a spot treatment in non-planted areas, but UC IPM points out that it is non-selective and will injure turf and ornamentals it touches. Follow the label.

Oxalis control options compared

Here’s every method side by side, including where each one falls short.

Is oxalis edible or toxic?

Can you eat it? Woodsorrel leaves, flowers and green pods have a sharp, lemony taste, and NC State Extension lists them as edible.

The same source warns that all parts contain soluble calcium oxalates. The risk is rated low, but eating large quantities can be harmful, and the plant is listed as a concern for cats, dogs and horses, with kidney damage possible if a lot is eaten.

Treat it as a small garnish at most, never as a leafy green, and do not eat it from lawns that have been sprayed.

Where this applies

The germination and spraying windows above come mainly from the United States: cool-season lawns in the North and Midwest, warm-season lawns in the South, and California for Bermuda buttercup.

In warm-season turf, check that a product is safe for your grass before use. In the tropics and the Southern Hemisphere, woodsorrel follows your own cool, moist season rather than calendar months. Herbicide registrations differ between countries and states, so use only products labelled for your site and grass type where you live.

A note from the agronomist’s side

If there’s one idea to take from oxalis biology, it’s that when you weed matters more than how hard you weed. A plant that can flower about 4 weeks after it germinates, and then fling seed several feet, punishes late weeding twice. Pull it in midsummer when the capsules are ripe, and the act of pulling sows the next crop.

The numbers above add up to a simple rhythm:

• Weed little and often while plants are small. Hand-weeding works best at 6 weeks old or younger, and seedlings can flower in about 4, so a pass every two to three weeks keeps you ahead of the pods.
• Treat any plant with capsules as a seed packet. Bag it; don’t compost it.
• Take the light away. Mulch in beds, dense turf in lawns.
• In lawns, spray the survivors young and plan the repeat 3 to 6 weeks later.

Inherited a heavy infestation? Year one is about stopping seed, not a perfect bed.

FAQ

What kills oxalis down to the root?

In lawns, a selective herbicide containing triclopyr or fluroxypyr moves into the plant and controls established plants, often with a repeat application. In beds, careful forking out of the taproot and runners over several weedings is the most reliable method without chemicals.

Is oxalis bad for a lawn?

It does no direct harm, but it fills gaps that grass should occupy and spreads quickly by seed. A few plants in a thin lawn are a sign the turf needs thickening. More weed profiles are in our lawn weeds identification hub, and creeping lawn weeds with a different leaf shape are covered in how to get rid of creeping Charlie.

Related guides: Purslane: Weed or Vegetable? How to Identify, Control and Eat It Safely · How to Get Rid of Chickweed in a Vegetable Garden (and Keep It Gone) · How to Get Rid of Creeping Charlie (Ground Ivy) in Your Lawn

Sources

• UC Statewide IPM Program. Creeping Woodsorrel and Bermuda Buttercup: Pest Notes (Publication 7444).
• Penn State Extension. Lawn and Turfgrass Weeds: Yellow Woodsorrel (Oxalis stricta L.).
• Clemson Cooperative Extension, Home & Garden Information Center. Oxalis Control.
• Kansas State University Turf and Landscape. Yellow Woodsorrel (Oxalis stricta) Control.
• University of Maryland Extension. Oxalis (Yellow Woodsorrel) Weeds.
• NC State Extension Gardener Plant Toolbox. Oxalis corniculata.
• NC State TurfFiles. Yellow Woodsorrel.
• University of Florida IFAS Extension. Biology and Management of Oxalis (Oxalis stricta) in Ornamental Crop Production (ENH1253).
• Marble, S.C., Gilliam, C.H., Wehtje, G.R. and Samuel-Foo, M. (2013). Early postemergence control of yellow woodsorrel (Oxalis stricta) with residual herbicides. Weed Technology 27(2): 347–351.