Bittercress may be small and short-lived but its ability to produce and disperse large amounts of seed makes it an exacerbating weed. Often introduced unwittingly on the compost of container plants, it can be hard to be rid of in a garden.
Latin name Cardamine hirsuta (hairy bittercress), C. flexuosa (wavy bittercress)
Areas affected surface of containers, bare soil, paths
Main causes weed with explosive seed capsules
Timing remove whenever seen
What is bittercress?
Hairy bittercress (Cardamine hirsuta) (see image above) is an annual species, common throughout the British Isles, particularly on bare ground, path-sides, and on walls. It often grows on the surface of containers in nurseries and garden centres and the seeds can be introduced into gardens unwittingly with container-grown plants.
Wavy bittercress (Cardamine flexuosa) (see image below) is a biennial or perennial plant, common in moist shady places, such as by streams, throughout the British Isles. It may occasionally be troublesome in gardens, usually in moist or poorly drained soils.
The leaves and flowers of both species of bittercress have a peppery, cress-like flavour and can be added to salads. Wavy bittercress flowers are visited by hoverflies, butterflies (eg. Green-veined White and Orange-tipped) and flea beetles.
However, bittercress can spread quickly by seed, so this page looks at options for gardeners when it is becoming a problem.
Related to the pretty cuckoo flower (Cardamine pratense), bittercress is a much drabber plant with insignificant white flowers and pinnate leaves. The arrangement of flowers and seed heads is typical of members of the mustard family (Brassicaceae).
Hairy bittercress (C. hirsuta) is the smaller of the two, sometimes growing just a few centimetres. Wavy bittercress (C. flexuosa) can grow strongly to reach around 50cm (18in) in height in damp conditions but is usually shorter in gardens.
Bittercress has an explosive seed mechanism by which seeds can be dispersed up to 1m (3ft) away or considerably further if carried by the wind. As with all annual weeds it is essential to destroy it before seed can be produced.
Cardamine hirsuta has a short life cycle. Seedlings may appear at most times of the year, but mainly in the summer or early autumn. As it is frost hardy it can survive the winter and will flower as temperatures rise in early spring, producing several generations in a season. Cardamine flexuosa is longer-lived but is less common as a weed in gardens.
The RHS believes that avoiding pests, diseases and weeds by good practice in cultivation methods, cultivar selection, garden hygiene and encouraging or introducing natural enemies, should be the first line of control. If chemical controls are used, they should be used only in a minimal and highly targeted manner.
Cultural control methods are more successful if applied before the weed has had time to set seed. Where infestations of bittercress are light, fork out before the weed sets seed. Among ornamentals or vegetable crops, careful hoeing or hand weeding is the only practical means of destroying either weed. If, however, they have been allowed to seed, they may remain a recurring problem for some time.
On borders or bare soil, a deep mulch (15cm (6in)) of organic matter such as garden compost or bark should help suppress the weed.
On unplanted land and path-sides contact weedkillers such as acetic acid (Weedol Gun Fast Acting), fatty acids (SBM Job Done Garden Ultrafast Weedkiller) and pelargonic acid (Doff 24/7 Fast Acting Weedkiller) can be used to control the annual species Cardamine hirsuta.
With heavier infestations of Cardamine flexuosa apply the herbicide glyphosate (e.g. Roundup Fast Action, SBM Job done General Purpose Weedkiller or Doff Advanced Weedkiller), letting the weed grow to flowering stage before application. When using glyphosate take care to avoid leaves and other green parts of all garden plants as it is not selective in action. Used with care, glyphosate can be used around the base of non-suckering woody plants, as long as the bark is woody, brown and mature. Glyphosate is not active through the soil and there is therefore no risk garden plants will absorb it through their roots.
Inclusion of a weedkiller product does not indicate a recommendation or endorsement by the RHS. It is a list of products currently available to the home gardener.
Weedkillers for gardeners (Adobe Acrobat pdf document outlining weedkillers available to gardeners; see section 3a and 4)
The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.