Wood-sorrel

How to recognise it

Habit

Low perennial of 5–15 cm with a creeping, branched rhizome; forms loose carpets.

Leaves

Three-parted like clover, with three inverted heart-shaped leaflets of 1–2 cm on a long, thin stalk; light green, sometimes purplish underneath. They fold down at night, in rain and in bright sun.

Flowers

One flower per stalk, 1–2 cm across, with five white petals with fine lilac to purple veins; April–May. Later in summer there are sometimes small closed flowers near the ground that pollinate themselves.

Fruit

A small capsule that bursts open when ripe and shoots out the seeds.

Roots

A thin, creeping rhizome with fleshy scales, just below the leaf litter.

Confusion with

Clovers have oval leaflets that do not fold and flowers in heads. Procumbent and upright yellow sorrel are garden weeds with yellow flowers, often in paving cracks and sunny beds.

Flowering: April–May

Why grow it?

• Flowers in April–May on the woodland floor, where few other flowers grow in the shade.
• Grows where almost nothing else will: in deep shade under trees and shrubs.
• Forms a fine green carpet that covers the soil and keeps it moist.
• A typical plant of ancient woodland: where it grows, the woodland floor has often been undisturbed for a very long time.
• The leaves move: they fold at night, in rain or in bright sun, which is fun to watch with children.

Wood-sorrel: where does it grow best?

• In the wild: old deciduous and coniferous woods, shady banks, sunken lanes, mossy tree stumps and stream banks in woodland.
• In the garden: light to deep shade, under trees or shrubs.
• Moist, humus-rich, slightly acid soil with leaf litter; in sun it dries out quickly.
• Lovely as ground cover in a shade garden, among ferns, under hedges or on a mossy stump.

Goes well with

• Wood anemone: Flowers just before or at the same time on the same woodland floor.
• Lady fern: Fine green fronds above the low carpet.
• May lily: Another small plant of acid woodland soils, with white spikes in May.
• Lily of the valley: Fragrant white bells in May, in the same shade.
• Early dog-violet: Small blue-violet flowers in April, on the same woodland edge.

Wood-sorrel: when and how to plant it?

1. Buy potted plants from a native-plant nursery, or ask for a piece of rhizome from someone who has it in their garden.
2. Plant in March–April or September–October, shallowly, just below the leaf litter.
3. Set the plants 15–20 cm apart; they slowly grow into a carpet.
4. Mix some leaf mould into the soil and cover with a layer of leaves.
5. Keep the soil moist in the first year, especially in a dry spring.
6. Never dig up plants in the woods: the rhizomes are fragile and a woodland floor recovers only slowly.

Care

Water

Water in long droughts; in a moist, shady corner it is otherwise not needed.

Feeding

Not needed. Fallen leaves are its natural food.

Leaf litter

Leave the autumn leaves: they protect the rhizomes and keep the soil moist.

Hoeing

Do not rake or hoe between the plants: the rhizomes lie just below the surface.

Competition

Keep brambles and vigorous grasses away, as it cannot compete with them.

Tip: Leave the autumn leaves where wood-sorrel grows: you mimic the woodland floor and the carpet will spread by itself.

Pruning and mowing

When: Not needed. It does not need cutting or mowing.

How:

• Simply leave the leaves; in mild winters they stay partly green.
• Leave fallen leaves from trees and shrubs as a natural mulch.
• Only remove branches or thick layers of coarse leaves that smother the carpet completely.

Pruning calendar and basic rules

Propagation

Division

In March or September slice off a piece of the carpet with its rhizome and replant it shallowly elsewhere.

Seed

Sow fresh seed in summer or autumn on moist, humus-rich soil in shade, barely covered.

Wood-sorrel: how does it get through the winter?

Hardy to −30 °C.

• In mild winters the leaves stay partly green; in hard frost they die back and reappear in spring.
• The rhizome overwinters under the leaf litter and is very hardy.
• The low carpet and the litter above it shelter small soil creatures.

Diseases and pests

• Drying out: In sun or drought the leaves turn yellow and shrivel. Choose a shady, moist spot and leave the leaf litter.
• Slugs: They sometimes eat the young leaves in spring; the damage is usually minor.
• Smothering: Brambles, ivy or tall grasses can smother the carpet. Keep them cut back around it.
• Mix-up with weeds: The yellow-flowered sorrels of paving and beds spread aggressively in gardens. Wood-sorrel is not a problem plant: it stays in the shade and spreads slowly.

Through the year

• March: Plant or divide. New leaves unfold.
• April: Flowering begins. The leaves fold at night and in rain.
• May: Full flower. Leave the leaf litter in place.
• June: Small closed flowers near the ground. Water in dry spells.
• July: Capsules shoot out their seeds. Water in dry spells.
• September: Plant or divide. Sow fresh seed.
• October: Leave autumn leaves as mulch.
• December: Resting under the leaf litter.

Did you know?

• Oxalis comes from the Greek oxys, sour. Oxalic acid is even named after this group of plants.
• Old folk names include cuckoo’s bread and alleluia: it flowers around Easter and when the cuckoo returns.
• It is sometimes put forward as the original shamrock of St Patrick in Ireland, although the shamrock is usually a clover.