Charlock

How to recognise it

Habit

Upright annual of 30–80 cm, sometimes up to 1 m, with branched stems.

Leaf

Lower leaves large, rough and hairy, with a big end lobe and a few smaller side lobes. Upper leaves undivided, coarsely toothed and not clasping the stem.

Flower

Bright yellow, 1.5–2 cm across, with four petals in a cross. The sepals spread horizontally. From May to September.

Fruit/Seed

Pod of 2.5–4.5 cm with a conical beak about a third of its length; round, dark brown to black seeds.

Stem

Rough at the base, with stiff, spreading hairs.

Confusion with

Oilseed rape has blue-green, hairless leaves that clasp the stem. White mustard has deeply divided leaves and hairy pods with a flat, sword-shaped beak. Wild radish has pale yellow or white flowers with dark veins and pods that are constricted between the seeds.

Flowering: May–September · Pruning: July–August

Why grow it?

• Rich source of nectar and pollen for honeybees, bumblebees, solitary bees and hoverflies from May onwards.
• Food plant for the caterpillars of whites, such as the large white, small white and green-veined white.
• The seeds are food for farmland birds such as finches and linnets.
• A characteristic plant of flower-rich field margins, together with poppy and cornflower.
• The young leaves were once eaten as a vegetable, and the seed was sometimes used as a substitute for mustard.

Charlock: where does it grow best?

• In the wild: fields, field margins, waste ground, building sites, dykes and verges.
• Full sun.
• Rich, limy or neutral loam and clay; less on poor, acid sand.
• In the garden: a cornfield flower border, a flower patch you lightly cultivate every year, or temporarily on a bare plot.

Goes well with

• Common poppy: Red next to yellow in the same field margin.
• Cornflower: A blue accent and another bee plant of arable land.
• Scented mayweed: White flower heads on the same cultivated soil.
• Field pansy: A small, low cornfield flower between the taller plants.

Charlock: when and how to plant it?

1. Charlock often comes up by itself after soil has been dug: the seed was already in the ground.
2. If you want it in a cornfield flower border, buy seed from a nursery or seed supplier for native plants. Never dig plants up from the wild.
3. Sow in March–May on loosened, weed-free soil: scatter thinly and rake in lightly.
4. Thin to 15–20 cm between plants and water until the seedlings are sturdy.
5. Do not sow it in or next to a vegetable plot with brassicas: it shares diseases and pests with them.
6. Cultivate the border lightly every year: without soil disturbance charlock disappears.

Care

Water

Not needed.

Feeding

Not needed: on rich soil it grows large by itself.

Spreading

In the vegetable garden, hoe off the seedlings. Do not let it set seed, as the seed stays in the soil for years.

Digging

The less you dig, the less charlock germinates: the seed mainly germinates when it is brought to the surface.

Letting it seed

In a cornfield flower border, let some of it self-seed for next year.

Tip: Dig as little as possible in the vegetable garden: charlock seed waits in the soil and only germinates when you bring it up. In a cornfield flower border, do exactly the opposite and cultivate the soil lightly every year.

Pruning and mowing

Pruning months: July–August.

When: No pruning. To prevent self-seeding, mow or pull the plants in July–August, as soon as the first pods have formed and before they ripen.

How:

• Pull or mow flowering plants before the pods turn brown.
• In a cornfield flower border, leave some standing until the seed is ripe, for the birds and for next year.
• Mown plants with green pods can still ripen seed: take them away if you do not want new charlock.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Seed

Each plant produces hundreds of seeds, which can survive in the soil for decades. They germinate mainly in spring, after the soil has been cultivated.

Charlock: how does it get through the winter?

Hardy to −10 °C: protect in harsh winters.

• The plant dies after setting seed; the seed overwinters in the soil.
• Late seedlings from autumn tolerate light frost but usually die in severe frost.
• Old stems with pods still offer seed to birds in autumn.

Diseases and pests

• Clubroot: Charlock is a brassica and can keep clubroot and other cabbage diseases going. Weed it out in and around the vegetable garden.
• Flea beetles: Tiny jumping beetles make small holes in the young leaves. Keeping the soil moist helps.
• Cabbage whites: They lay their eggs on it. Protect your cabbages with insect mesh; the charlock in the field margin can stay.
• Pollen beetles: Small black beetles feed on the flower buds. Harmless in a wild margin.
• Seed bank: One year of self-seeding means years of work. Do not let a single plant set seed in the vegetable garden.

Through the year

• March: Sow in a cornfield flower border. Hoe off seedlings in the vegetable garden.
• April: Hoe. Sow.
• May: Flowering begins: bees and hoverflies on the flowers.
• June: Full flower. Cabbage whites lay eggs.
• July: Pods are forming. Mow or pull if you do not want seed.
• August: Last cut before the pods ripen. Collect seed in the border.
• September: Last flowers. Lightly cultivate the cornfield flower border.
• October: The plants die; birds eat the seed.

Did you know?

• Charlock seed can survive in the soil for decades; that is why disturbed ground and new road verges sometimes turn yellow almost overnight.
• ‘Sinapis’ is the old Latin name for mustard, and ‘arvensis’ means ‘of the fields’.
• Before modern weed control, cereal fields were often yellow with charlock; it has since declined sharply in many fields.