Short, White Brassicas With Long Seed Pods

Hairy Bitter-cress Wavy Bitter-cress Wild Radish Thale Cress

What are they?

This page covers members of the brassica family that typically grow less than 50cm in height and have white - usually rather small - flowers. They all share the same general appearance of four-petalled, white flowers that are followed by elongated, slender seed pods. For identification purposes, it is wise to wait until seed pods have started to develop, as this will narrow your search.

Where are they found?

This is a group of only loosely related plants, so there is much variation in the habitat choices, from urban habitats to roadsides, heaths and saltmarshes. However, the habitat can be a valuable aid to identification for some species - especially the coastal ones, so be sure to check these details in the individual species notes below.

Identification

All these plants have white, four-petalled flowers and elongated seed pods, so you need to look elsewhere for identification clues. Most important will be details of the leaves - both basal and those on the flowering stems, while tiny differences in the flowers and the pods can help with closely related species, such as the bitter-cresses. As noted above, the habitat and location is also often useful to note.



Thale Cress      Arabidopsis thaliana

A native species which is widespread and common to abundant in a wide range of open habitats, particularly disturbed ground, pavements, walls and other urban habitats. Flowers March to July. A tiny species growing to 30cm, but often much less and often only 2-3cm tall. Basal leaves entire or slightly toothed, grey-green and roughly hairy. Overall very similar to the bitter-cresses, but the whole plant is grey-green and slightly waxy, and the seed pods are held well away from the main stem (not close to it).

Thale Cress Thale Cress Thale Cress Thale Cress
Habit
Flowers
Basal leaves
Seed pods held away from stem


Hairy Bitter-cress      Cardamine hirsuta

Native. Widespread and often abundant as a weed of any type of open ground, especially in gardens, nurseries and similar places. Flowers mostly March to July but a few plants can be found in flower more or less throughout the year. Flowers rather small and often not opening fully; only four stamens, with the two shorter ones being absent. Leaves compound, the basal ones usually with a few bristly hairs on the petiole (hand lens may be needed!). Stems relatively straight (not clearly zigzagging), hairless. Seed pods long and numerous and carried erect and quite close to the main stem. Compare very carefully with Wavy Bitter-cress (some individuals may be impossible to correctly identify between these two species).

Hairy Bitter-cress Hairy Bitter-cress Hairy Bitter-cress Hairy Bitter-cress
Flowers with only four stamens
Basal leaf
Bristly leaf petiole
Long, upright pods


Wavy Bitter-cress      Cardamine flexuosa

Native. Typically a plant of wet flushes and muddy streamsides, especially in shady places, but increasingly becoming a plant of gardens and urban areas. Flowers mostly May to September but occasionally other times. Flowers rather small and often not opening fully; six stamens (two short, four long). Leaves compound, the basal ones usually with hairless petioles (hand lens may be needed!). Stems usually clearly zigzagging, hairy. Seed pods long and numerous and carried erect and quite close to the main stem. Compare very carefully with Hairy Bitter-cress (some individuals may be impossible to correctly identify between these two species).

Wavy Bitter-cress Wavy Bitter-cress Wavy Bitter-cress Wavy Bitter-cress
Habit
Flowers with six stamens
Basal leaf
Hairy, zigzag stem


Large Bitter-cress      Cardamine amara

A native of damp soils, usually avoiding chalky areas. Widespread, though local, along streams and ditches and especially around damp places in woodland and scrub. Flowers April to June. A showy species and much larger than other bitter-cresses; often grows in quite large colonies along muddy waterside edges. Leaves are compound, the basal leaves with rounded lobes and those of the stems more angular and narrower. Seed pods long, linear and upright. When in full flower, the violet (not yellow) anthers are very distinctive.

Large Bitter-cress Large Bitter-cress Large Bitter-cress Large Bitter-cress
Habit
Flowers
Flower with violet anthers
Basal leaf


New Zealand Bitter-cress      Cardamine corymbosa

Introduced from New Zealand. First recorded in the British Isles in 1985 and slowly spreading as a horticultural contaminant to paths and flowerbeds in urban areas. Still only a handful of records for our region but likely to increase, although its tiny size makes it easily overlooked. Flowers March to June and perhaps at other times. A very tiny (no more than 10cm and often much less) and rather peculiar plant that may grow as simple stems with no leaves and a single, sometimes petalless, flower. Leaves, when present, are compound but only with three to seven leaflets. When present, mature flowers are larger than those of other, small bitter-cress species, with pure white, fully-opening petals, borne singly.

New Zealand Bitter-cress New Zealand Bitter-cress New Zealand Bitter-cress
Habit
Flower
Basal leaf


Hairy Rock-cress      Arabis hirsuta

Native in areas of chalky grassland. In our region, largely confined to Breckland, where it can be locally common, with a scattering of smaller populations on chalky grassland elsewhere. Flowers April to September. A small plant with basal leaves very similar to those of Thale Cress, but the stem leaves are also hairy. The long pods are held erect, like those of bitter=cresses, but are flattened in one plane.

Hairy Rock-cress Hairy Rock-cress Hairy Rock-cress Hairy Rock-cress
Habit
Flowers
Basal leaf
Seed pods


Caucasian Arabis      Arabis caucasica

Introduced from eastern Europe and popular as a trailing plant on rockeries and garden walls. Occasionally found on walls or banks away from gardens, perhaps where garden waste has been tipped. Flowers March to May. Very like a white-flowered Aubretia and often grown in gardens with that species. Differs from Aubretia in its elongated seed pods and its larger leaves.

Caucasian Arabis Caucasian Arabis
Habit
Flowers


Common Water-cress      Nasturtium officinale

Widespread throughout our region and often common in streams, ditches and along smaller rivers. A native species, but also much cultivated. Flowers May to October. Forms low mats of full, leafy vegetation in usually flowing water, with clustered heads of white flowers. Water-cresses as a group are easily recognised but the two species are very difficult to tell apart and often indistinguishable. To be sure of the species, select mature seed pods and check if the seeds inside are in a single or a double row. In this species, the seeds are in a double row.

Common Water-cress Common Water-cress Common Water-cress
Habit
Flowers
Leaves


Narrow-fruited Water-cress      Nasturtium microphyllum

A native species, but the distribution is hard to assess due to confusion with the far more plentiful Common Water-cress. Flowers May to October. Forms low mats of leafy vegetation in usually flowing water, with clustered heads of white flowers. Water-cresses as a group are easily recognised but the two species are very difficult to tell apart and often indistinguishable. To be sure of the species, select mature seed pods and check if the seeds inside are in a single or a double row.

Narrow-fruited Water-cress Narrow-fruited Water-cress Narrow-fruited Water-cress Narrow-fruited Water-cress
Habit
Flowers
Leaf
Seeds in a single row


Wild Radish      Raphanus raphanistrum subsp. raphanistrum

Probably an ancient introduction from Neolithic times and now a widespread and common plant throughout most of our region on a wide range of disturbed ground, field margins, waste places, tips and similar locations. Flowers May to September. Once known, this is an easy plant to recognise, with its coarse, bristly leaves and stems and its seed pods that have faint ribbing between the developing seeds. Plants are often relatively short, but usually have spreading branches, making them more noticeable and obvious than the species covered under the small, white brassicas. Flowers usually have dark veins and populations usually have a mix of both white and pale yellow flowered plants among them. The petals have long bases to them, forming a distinct cross shape to the flower.

Wild Radish Wild Radish Wild Radish Wild Radish
Flower
Flower
Basal leaves
Seed pod