Common whitlowgrass

How to recognise it

Growth habit

Tiny annual of 2–20 cm, usually 5–10 cm, with a flat rosette of leaves and one or more thin, leafless flowering stalks.

Leaf

Only in a rosette: lance- to spoon-shaped leaves of 0.5–2 cm, with a smooth or slightly toothed edge, covered with forked or star-shaped hairs.

Flower

White, 3–6 mm, with four petals that are each deeply split in two, so it looks as if it has eight. Flowers from February to May. In bad weather and at night the flowers nod and close.

Fruit/Seed

Flat, oval pods of 3–9 mm on long stalks, holding many tiny seeds. When they split open, a silvery, translucent partition is left behind.

Roots

A thin, short root: the plant comes away at the slightest pull.

Confusion with

Thale cress has whole, unsplit petals and long, narrow pods. Hairy bittercress has pinnate leaves and long, upright pods. Only whitlowgrass has split petals and short, flat pods.

Flowering: February–May

Why grow it?

• One of the first flowers of the year: from February–March a little nectar and pollen for small bees, flies and hoverflies.
• A true plant of towns and driveways: it grows where almost nothing else will, between stones and on walls.
• Takes up no space: by May it has gone, just when other plants need the room.
• A fine example of how plants avoid the dry summer: germinating in autumn, flowering in spring and surviving as seed.
• Free and spontaneous: if you weed paving and gravel paths only in June, it comes back every year.

Common whitlowgrass: where does it grow best?

• In the wild: dunes, open sandy ground, dry grassland, walls, rocks, railway land, gravel paths and cracks in paving.
• Full sun, in an open spot without tall grass.
• Dry, poor, sandy or gravelly soil; also on limestone and in old walls.
• In the garden: a gravel garden, between patio slabs or paving bricks, on a green roof, a low wall or a sandy edge.

Goes well with

• Biting stonecrop: Yellow cushions between the stones, flowering long after the whitlowgrass has gone.
• Little mouse-ear: Another tiny spring plant of open sand.
• Common stork’s-bill: Flowers on the same sand, from April into summer.
• Large thyme: Fragrant purple cushions for a sunny gravel garden.

Common whitlowgrass: when and how to plant it?

1. Usually you do not need to sow it: it turns up by itself if you do not weed or pressure-wash open sandy patches and cracks.
2. If you do want to sow it, buy seed from a native plant nursery or take a few ripe pods in May from your own garden or a neighbour’s. Do not dig up plants from the wild.
3. Sow in September–October: scatter the dust-fine seed on bare, sandy soil or in cracks and press it down; do not cover it.
4. In dry weather, water a little now and then after sowing until the seedlings appear.
5. No fertiliser, no compost and no mulch: otherwise the bare patches it needs disappear.
6. Moving plants is pointless: they live only briefly and have a fragile root.

Care

Water

Not needed: it grows and flowers in the wet spring and has gone by summer.

Feeding

Do not feed: on rich soil other plants grow over it.

Weeding

Do not weed paving cracks and gravel paths in February–May, or weed carefully around the rosettes.

Letting it seed

It only survives as seed: let the plants die off in May and shed their seed.

Keeping it open

Lightly scratch over the spot once in summer, so bare patches remain where the seed can germinate in autumn.

Tip: Wait until June to weed your drive, patio and gravel paths: by then the whitlowgrass has flowered and set seed, and it will come back every spring.

Pruning and mowing

When: Not needed.

How:

• No need to prune or cut back: after setting seed in May the plant dies off by itself.
• Leave the dead plants where they are; they disappear within a few weeks.
• Only mow or weed gravel paths and paving cracks in June, after the seed has dropped.

Pruning calendar and basic rules

Propagation

Seed

It self-seeds. Collect ripe pods in May, store them dry and scatter the seed in September–October on open, sandy soil.

Common whitlowgrass: how does it get through the winter?

Hardy to −25 °C.

• The seed germinates in autumn; the little rosettes overwinter between stones or on the sand.
• Fully hardy: the rosettes withstand hard frost.
• In mild winters the first plants already flower in February.

Diseases and pests

• Weeded out: It is often scraped out as a weed. Only weed paving cracks in June, or leave a few spots alone.
• Overgrown: It disappears in tall grass or under a layer of compost. Keep the spot poor and open.
• Pressure washers and flame weeders: Spraying and burning remove not only moss but also rosettes and seed. Leave a few strips untouched in spring.

Through the year

• February: The first little flowers in mild weather.
• March: Full bloom: small bees and flies on the flowers.
• April: Flowers and the first pods. Do not weed paving cracks yet.
• May: Seed ripens and drops; the plants die off. Collect pods.
• June: Weed paving cracks and gravel paths: the seed is already in the ground.
• September: Sow on open, sandy spots.
• October: Seedlings and young rosettes appear.
• December: The rosettes overwinter.

Did you know?

• Each of the four petals is deeply split, which makes the little flower look as if it has eight.
• The English name whitlowgrass refers to an old belief that the plant could cure a whitlow, an inflammation of the finger.
• It is a true winter annual: it germinates in autumn, flowers in early spring and has gone by May, so it spends the dry summer as seed.