How to Kill Bittercress

Bittercress is one of those common UK weeds that seems to appear from nowhere. One week your borders look clean, the next there are rosettes of small green leaves everywhere you look. The culprit is usually hairy bittercress (Cardamine hirsuta), and its ability to colonise a garden so quickly comes down to one remarkable feature: exploding seed pods.

Unlike most weeds that simply drop their seeds or rely on wind dispersal, bittercress has evolved a ballistic mechanism. When the seed pods (called siliques) mature, they’re under tension. The slightest touch – your hand brushing past, a gust of wind, even raindrops – triggers them to split and coil, catapulting seeds at speeds of up to 10 metres per second. Those seeds land up to a metre away from the parent plant, ready to germinate within days.

This is why timing matters more with bittercress than almost any other weed. Once those pods have fired, you’re not dealing with one plant anymore – you’re dealing with next year’s infestation.

Why Bittercress Spreads So Fast

The numbers behind bittercress are sobering. A single plant produces between 600 and 5,000 seeds. Those seeds become sticky when wet, hitching rides on tools, boots, clothing, and even pets. They survive in soil for years, waiting for the right conditions.

Bittercress also completes its entire lifecycle remarkably quickly – sometimes in just five to six weeks from germination to setting seed. In a single growing season, multiple generations can emerge. This is why the old gardening saying applies perfectly here: one year’s seeding means seven years weeding.

The weed thrives in cool, moist conditions, which is why autumn and early spring see the biggest flushes of new seedlings. It loves disturbed soil, paving cracks, container compost, and any bare patches in borders or lawns. If you’re battling bittercress on patios or paths, the same timing principles apply. Nursery-bought plants are a common source – bittercress seeds frequently contaminate pot surfaces and compost, so always check new purchases before planting.

Bittercress is one of the most common garden weeds in the UK, often appearing alongside other fast-spreading annuals like chickweed.

Identifying Bittercress

Hairy bittercress grows as a low rosette of leaves, typically staying close to the ground until it sends up flowering stems. The leaves are compound, with small rounded leaflets arranged along a central stem, and the terminal leaflet (at the tip) is usually the largest.

The flowers are small and white with four petals – a characteristic of the mustard family. They appear on slender upright stems, typically from late winter through to early summer, though mild winters can see flowering almost year-round. After flowering, the elongated seed pods develop along the stems. These siliques start green and may turn slightly purplish as they mature – that’s your warning sign that they’re primed to explode.

A related species, wavy bittercress (Cardamine flexuosa), looks very similar but has wavier leaf margins. Both behave the same way and respond to the same control methods.

When to Remove Bittercress

The window for effective bittercress control is before flowering. Once you see those small white flowers, you’re already racing against the clock. Once the seed pods form and mature, any disturbance triggers seed dispersal.

The best times to tackle bittercress are autumn (when seedlings emerge after late summer germination) and early spring (before the overwintered plants flower). During mild winters, it’s worth checking your borders regularly – bittercress doesn’t stop growing just because temperatures drop.

If you find plants that have already set seed, approach them carefully. Don’t pull or disturb them. Instead, cover them with a bag or cloth before removal to contain any seeds that fire during handling. Alternatively, use a systemic weedkiller to kill them in place before they mature further.

How to Get Rid of Bittercress

The approach depends on where the bittercress is growing and how established the problem is.

Hand Pulling

For small infestations caught early, hand weeding works well. The key is to remove plants at the rosette stage, before flowering. Bittercress has a relatively shallow, fibrous root system that comes away easily when the soil is damp. A day or two after rain is ideal.

Don’t be fooled by the small size of young plants – if you leave them, they’ll flower and set seed within weeks. Regular patrols through autumn and early spring, pulling any rosettes you find, will steadily reduce the seed bank in your soil.

Hoeing

For larger areas, hoeing is faster than hand pulling. The aim is to sever the plants at or just below soil level, cutting the top growth from the roots. A sharp hoe blade makes this quicker and more effective. Hoe on a dry day so the severed plants desiccate rather than re-rooting.

Never hoe bittercress that has already flowered or set seed – you’ll just scatter seeds across a wider area.

Weedkiller

For established infestations in borders, paths, or patios, a systemic weedkiller containing glyphosate kills bittercress effectively. The chemical is absorbed through the leaves and transported throughout the plant, killing roots and all.

Spot-spray individual plants or patches rather than blanket-spraying, and avoid contact with plants you want to keep. Glyphosate is non-selective, meaning it kills any plant it touches. Apply when bittercress is actively growing (spring or autumn) for best uptake.

For bittercress in lawns, a selective lawn weedkiller containing 2,4-D, MCPP, or dicamba will target the broadleaf weed without harming grass. Apply when the bittercress is young and actively growing.

Mowing

Regular mowing can help control bittercress in lawns by removing flower heads before they develop into seed pods. However, bittercress rosettes grow low to the ground and can flower below typical mowing height, so mowing alone rarely eliminates the problem completely. Combine it with spot treatment or overseeding to thicken the turf.

Preventing Bittercress

Prevention is far easier than cure with bittercress. The goal is to eliminate the conditions it needs: bare soil, disturbed ground, and gaps where seeds can germinate.

Mulching is your best defence in borders. A layer of bark mulch, wood chips, or well-rotted compost at least 5-8cm deep suppresses germination by blocking light and creating a physical barrier. Top up mulch annually to maintain coverage.

In lawns, a thick, healthy sward leaves no room for bittercress to establish. Overseed thin patches, feed regularly, and avoid scalping with the mower. Bittercress exploits weakness – a vigorous lawn resists invasion. The same approach helps control other lawn weeds like dandelions and clover.

Always inspect container-grown plants before adding them to your garden. Scrape off the top couple of centimetres of compost if you see any sign of bittercress or other weeds, and dispose of it rather than composting.

Frequently Asked Questions

Why does bittercress spread so fast?

Bittercress has explosive seed pods that fire seeds up to a metre away when triggered. Each plant produces 600-5,000 seeds, and the lifecycle can complete in just 5-6 weeks, allowing multiple generations per season.

When should I remove bittercress?

Remove bittercress at the rosette stage before it flowers. Once seed pods form, any disturbance triggers seed dispersal. The best times are autumn (when new seedlings emerge) and early spring (before overwintered plants flower).

Can you eat bittercress?

Yes, bittercress leaves are edible and have a mild peppery flavour similar to rocket. Harvest young leaves before flowering for the best taste. Only eat plants that haven’t been treated with weedkiller.

Will mowing control bittercress in lawns?

Regular mowing helps by removing flowers before they set seed, but bittercress rosettes often grow below mowing height. Combine mowing with spot treatment and lawn care to thicken the turf.

How long do bittercress seeds survive in soil?

Bittercress seeds form a persistent seed bank and can remain viable in soil for several years. This is why consistent control over multiple seasons is needed to exhaust the reservoir of dormant seeds.