How to Kill Oxalis (Wood Sorrel)

Oxalis, commonly known as wood sorrel, is one of the most frustrating weeds a gardener can face. Its innocent appearance masks a survival strategy that defeats most attempts at removal. The plant produces tiny underground bulbils that spread through the soil when disturbed, meaning the more you dig, the worse your problem becomes. It’s among the most persistent weeds found in British gardens.

There are over 800 species of oxalis worldwide. In UK gardens, the most troublesome are creeping wood sorrel (Oxalis corniculata) with its small yellow flowers and purple-tinged leaves, and the pink-flowered O. debilis and O. latifolia. All share the same maddening ability to regenerate from fragments you can barely see.

Why Oxalis is So Hard to Kill

The secret to oxalis’s persistence lies beneath the soil. Each plant produces numerous bulbils, tiny structures resembling miniature onions, attached to the roots. In some species, a single plant can produce 20 or more new bulbils in a season. These bulbils detach easily when you dig or pull the plant, scattering through the soil to produce new plants.

The bulbils can remain dormant in the soil for several years, waiting for the right conditions to sprout. Even after you think you’ve cleared an area, new plants emerge from bulbils you never knew were there. Rotavating or digging an infested area is the worst thing you can do. You effectively plant thousands of new oxalis across your entire bed.

To compound the problem, oxalis also spreads by seed. The seed pods explode when ripe, firing seeds away from the parent plant. Bittercress has similar explosive seed pods, though oxalis is far harder to eradicate. In mild weather, oxalis can flower and set seed almost year-round, constantly replenishing the seed bank in your soil.

Identifying Oxalis

Oxalis is often confused with clover, but the leaves are distinctly different. Both have three leaflets, but oxalis leaflets are heart-shaped with a notch at the tip. Clover leaflets are rounded. Oxalis leaves often fold downward in bright sunlight or at night, giving the plant a wilted appearance even when healthy.

Creeping wood sorrel, the most common problem species, has small five-petalled yellow flowers and spreads via runners that root as they spread. The leaves range from green to purple-bronze depending on conditions. The plant forms low mats that creep under other plants, making it hard to spot until well established.

Oxalis thrives in paving cracks, path edges, greenhouse borders and container plants. For oxalis in hard surfaces, see our guide to killing weeds on patios. It favours open habitats and doesn’t compete well in thick lawns or densely planted borders, which offers one route to control.

Don’t confuse problem oxalis species with our native wood sorrel (Oxalis acetosella). This woodland plant has white flowers with pink veins and grows in shady spots under trees. It’s not invasive and is actually a lovely addition to a woodland garden.

Hand Weeding Oxalis

For small infestations, careful hand weeding can work, but you must remove every bulbil. This means excavating the soil around each plant rather than simply pulling. Use a trowel to lift the entire root system along with surrounding soil, then sift through to remove all the tiny bulbils.

Work when the soil is moist, as bulbils are easier to see and less likely to break off. Never shake soil from the roots over your beds as this scatters bulbils everywhere. Instead, place the entire plant and surrounding soil into a bag for disposal. Don’t add oxalis to your compost heap. The bulbils survive home composting temperatures. Put them in your council green waste bin where industrial composting will destroy them.

Several weedings over a growing season are usually necessary. New plants will appear from bulbils you missed, and you’ll need to remove these before they mature and produce their own bulbils.

Smothering Oxalis

Where oxalis is widespread, smothering offers a more practical approach than hand weeding. The aim is to exclude light completely, starving the bulbils of the energy they need to survive.

The RHS recommends covering infested ground with a layer of cardboard, then adding at least 20cm of organic mulch such as bark chips or wood chips. Alternatively, use heavy-duty weed membrane beneath the mulch. The covering needs to remain in place for at least two years to exhaust the bulbils completely.

This method works best in areas you can take out of cultivation temporarily. For beds you want to keep planted, dense planting combined with regular mulching helps suppress oxalis. The weed doesn’t compete well in shade, so filling gaps in borders with ground cover plants reduces available growing space.

Using Weedkiller on Oxalis

Chemical control of oxalis is challenging. The RHS notes that weedkillers available to home gardeners aren’t particularly effective against oxalis, largely because the bulbils underground aren’t affected by sprays applied to the leaves.

That said, persistent treatment with glyphosate can weaken and eventually kill oxalis. Apply in spring when plants are growing actively and have plenty of leaf area to absorb the chemical. Use a fine spray to coat the leaves thoroughly. Spray in the evening to prevent evaporation and give maximum absorption time. For stubborn infestations, the strongest weed killer gives you the best fighting chance.

One application won’t be enough. Plan for repeated treatments over two or three growing seasons. Each application weakens the plants and reduces the bulbil reserves in the soil. Eventually, persistence wins.

The critical timing for any control method is what’s called the bulb exhaustion stage, just before or during flowering. At this point, the parent bulb’s food reserves are depleted and new bulbils aren’t yet developed enough to survive independently. Targeting plants at this stage gives the best chance of killing them outright. Triclopyr is another option for broadleaf weeds, though glyphosate remains the go-to for oxalis.

Preventing Oxalis

Oxalis often arrives in gardens on other plants. The weed grows on the surface of compost in pots, hitching a ride when you buy new plants. Always check the compost surface of any plant you bring home and remove any oxalis you find before planting.

Avoid disturbing soil in areas where oxalis has grown. Even after successful treatment, bulbils may remain dormant below. Minimise digging and use a no-dig approach where possible, adding organic matter as a surface mulch rather than incorporating it.

Maintain thick, healthy lawns and densely planted borders. Oxalis prefers open ground and struggles to establish in competitive environments. Regular feeding and overseeding of lawns, and close planting in borders, reduces opportunities for oxalis to gain a foothold.

Frequently Asked Questions

Is oxalis the same as clover?

No. Both have three leaflets, but oxalis leaflets are heart-shaped with a notch, while clover leaflets are rounded. Oxalis has yellow or pink flowers depending on species; most lawn clovers have white or pink ball-shaped flower heads. See our guide to killing clover in lawns for more on that weed.

Why does oxalis keep coming back after I pull it?

Oxalis produces tiny bulbils on its roots that detach when disturbed. Each bulbil can grow into a new plant. Unless you remove every single bulbil, new plants will keep appearing. Bulbils can also remain dormant in soil for years. Ground elder shares this frustrating ability to regenerate from root fragments.

Can I kill oxalis with vinegar?

Vinegar burns the leaves but doesn’t affect the bulbils underground. The plant simply regrows. For any chance of success, you need either complete physical removal of all bulbils, long-term smothering, or repeated systemic weedkiller treatment.

How long does it take to get rid of oxalis?

Expect a multi-year battle. Bulbils can survive in soil for several years, so even after apparently clearing an area, new plants may emerge. Most successful eradication programs take two to three years of consistent effort.

Should I dig up the soil to remove oxalis bulbils?

No. Digging spreads bulbils throughout your soil, making the problem worse. Either carefully hand weed individual plants with minimal soil disturbance, or smother entire areas with mulch. Avoid rotavating at all costs.

Oxalis tests every gardener’s patience, but it can be beaten. Start by stopping its spread, never let it flower and set seed, and choose either careful hand removal or long-term smothering. For chemical control, glyphosate applied repeatedly over several seasons can exhaust the bulbil reserves. Whatever approach you choose, consistency is everything. For other bulbil-producing weeds, see our guide to lesser celandine.