Kill Sheep’s Sorrel in Your Lawn

Sheep’s sorrel is more than just a lawn weed. It’s an indicator plant that tells you your soil is acidic and lacking in nutrients. This native British wildflower thrives in exactly the conditions that make grass struggle, spreading through creeping rhizomes to colonise neglected or poorly maintained lawns. It’s one of the common weeds in British gardens that reveals underlying soil problems.

Also known as red sorrel, field sorrel and sour weed, Rumex acetosella has been documented as a weed of cultivated land since the Bronze Age. Its persistence comes from an aggressive root system and seeds that can remain dormant in soil for up to 80 years. But understanding why it grows in your lawn gives you the key to controlling it.

Identifying Sheep’s Sorrel

Sheep’s sorrel grows as a rosette of distinctive arrow-shaped leaves at ground level. The leaves are small, typically 2-5cm long, with two pointed lobes at the base that give them their characteristic arrowhead shape. They’re green but often develop a reddish tinge, particularly in stressed conditions.

The leaves have a sour, lemony taste due to oxalic acid content, which gives rise to names like sour weed. They’re edible in small quantities and have been used as a salad ingredient and flavouring for centuries.

Flower spikes appear from May to August, reaching up to 50cm tall on slender, reddish stems. The tiny flowers start greenish and turn reddish-brown as they mature. Male and female flowers appear on separate plants, with female flowers being more prominently red.

In regularly mown lawns, flowering is often prevented, but the distinctive leaf rosettes remain visible among the grass. Don’t confuse sheep’s sorrel with common sorrel (Rumex acetosa), which is a larger plant with backward-pointing lobes on its leaves rather than outward-pointing ones.

Why It Grows in Your Lawn

Sheep’s sorrel is a strong indicator of acidic soil. It thrives at pH levels below 6 and struggles on chalky or limestone soils. If you have sheep’s sorrel in your lawn, your soil is almost certainly acidic.

The plant also indicates poor fertility. It flourishes in sandy, nutrient-depleted soils where grass grows weakly. Low nitrogen levels particularly favour sheep’s sorrel, as it can tolerate conditions that starve more demanding plants. Similar conditions favour other tough lawn weeds like yarrow.

These soil problems create a cycle. Poor conditions weaken the grass, creating gaps for sheep’s sorrel to colonise. The weed then spreads through its rhizome system, displacing more grass and making the problem worse.

Understanding this relationship is crucial for control. Killing the weed without addressing the underlying soil issues just creates space for it to return. Effective management combines weed removal with soil improvement.

Chemical Control

Sheep’s sorrel responds to selective lawn weedkillers, though it’s tougher to kill than many broadleaf weeds. Products containing 2,4-D, MCPA, dicamba or mecoprop can provide control, but multiple applications are usually needed.

Apply selective herbicide when the weed is actively growing, typically April to September. Ensure thorough coverage of all foliage. The rosette growth habit means some leaves may be hidden beneath grass, so a repeat application two to four weeks later improves results.

Be prepared for the weed to regrow from its rhizome system after initial treatment. The underground roots store enough energy to produce new shoots even when top growth is killed. Persistent follow-up treatment over two seasons is usually necessary for complete control.

For severe infestations where grass has been largely displaced, consider using glyphosate to clear the area completely before addressing soil issues and reseeding.

Physical Removal

Hand removal works for small infestations but requires patience and thoroughness. The shallow, spreading rhizome system makes complete removal challenging, as plants can regenerate from small root fragments left in the soil.

Use a hand fork to carefully lift plants, following the creeping roots as far as possible. The roots are fragile and break easily, so work slowly and methodically. Check the area regularly for regrowth and remove new shoots promptly before they can establish.

Avoid using a hoe or rotavator, as these chop roots into pieces and spread the problem. Each fragment can potentially grow into a new plant.

After removal, reseed any bare patches promptly. Bare soil invites recolonisation by sheep’s sorrel and other weeds.

Soil Improvement

Addressing the acidic, nutrient-poor conditions that favour sheep’s sorrel is essential for long-term control. Without soil improvement, the weed will return even after successful removal.

Test your soil pH before taking action. Home testing kits are inexpensive and give you a baseline to work from. Most lawns grow best at pH 6.0-7.0, while sheep’s sorrel prefers conditions below 6.0.

Apply garden lime to raise soil pH gradually. Spread evenly across the lawn in autumn or early spring, following package rates for your soil type. Lime takes several months to work through the soil, so don’t expect immediate results. Retest after six months and repeat if necessary.

Improve fertility through regular feeding. Sheep’s sorrel thrives in nitrogen-poor soil, so maintaining adequate nutrient levels helps grass compete more effectively. Apply a balanced lawn fertiliser in spring and autumn, following package directions.

Avoid acidifying fertilisers like sulphate of ammonia if sheep’s sorrel is a problem. These lower soil pH and create conditions the weed prefers.

Cultural Control

Healthy, dense turf competes more effectively against sheep’s sorrel. Following a proper UK lawn care routine reduces the gaps where weeds can establish.

Mow regularly at the correct height for your grass type. Taller grass shades the soil surface, making it harder for weed seeds to germinate. In most UK lawns, a cutting height of 25-40mm works well.

Overseed thin areas in autumn to thicken the turf. Dense grass leaves less space for weeds to colonise. Choose grass varieties suited to your conditions, including shade-tolerant types for shaded areas.

Improve drainage if waterlogging is a problem. Though sheep’s sorrel tolerates dry conditions, poor drainage weakens grass and creates opportunities for weeds. Aerate compacted soil and top-dress with sharp sand where needed.

Frequently Asked Questions

Does sheep’s sorrel mean my soil is acidic?

Yes. Sheep’s sorrel is a reliable indicator of acidic soil with pH below 6.0. It rarely grows on chalky or limestone soils. A soil test can confirm the pH level and guide lime application rates.

Will lawn weedkiller kill sheep’s sorrel?

Yes, selective herbicides containing 2,4-D, MCPA, dicamba or mecoprop can control sheep’s sorrel. However, multiple applications over two seasons are usually needed due to the plant’s ability to regrow from its rhizome system.

Why does sheep’s sorrel keep coming back?

The spreading rhizome system stores energy that allows regrowth even after top growth is killed. Additionally, seeds can remain dormant in soil for decades. Long-term control requires addressing the acidic, nutrient-poor soil conditions that favour the weed.

Is sheep’s sorrel edible?

Yes, the leaves are edible with a sour, lemony taste. They’ve been used in salads and cooking for centuries. However, they contain oxalic acid and should only be eaten in small quantities. People with kidney problems, gout or arthritis should avoid them.

How do I raise my lawn’s pH?

Apply garden lime in autumn or early spring, spreading evenly across the lawn. The amount needed depends on your starting pH and soil type. Test soil before and after treatment to monitor progress. Lime takes several months to work through the soil.

Sheep’s sorrel tells you your lawn needs help. Killing the weed is only part of the solution. Raising soil pH with lime and improving fertility with regular feeding addresses the underlying conditions that allow sheep’s sorrel to thrive. With the right soil balance, your grass can outcompete this persistent weed. For more lawn weed advice, see our guides to dandelions, docks, self-heal and creeping cinquefoil.