Tall, White Brassicas
What are they?
This page covers members of the brassica family that typically grow more than 50cm in height and have white - usually showy - flowers. Since the group includes a number of species that are not particularly closely related, they differ quite widely in their appearance, which should actually help with the identification process. They all share the family traits of four-petalled, white flowers that are followed by distinctive seed capsules.
Where are they found?
This is a group of only loosely related plants, so there is much variation in the habitat choices. 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, so you need to look elsewhere for identification clues. Check the seed capsules, if they are present, as well as leaf size and shape. As noted above, the habitat and location is also often useful to note.
Garlic Mustard Alliaria petiolata
Very common and widespread biennial of hedgerows, woodland edge and similar places. Flowers April to July. Often grows in large, extensive stands, setting large quantities of seed. Young plants germinate in late summer or autumn and produce a few basal leaves, then gain height and flower the following spring. The whole plant has a garlic smell and taste. Leaves broadly triangular with coarsely toothed edges, the overwintering leaves being rather dull, but fresh spring leaves are bright, shining green; seed capsules long and linear.
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Annual Honesty Lunaria annua
Introduced. A popular garden plant and often escaping into rough, grassy areas and roadsides. Flowers April to May. Flowers may be rich, pinkish-purple or white, with the two colours often (though not always) growing together. Leaves broadly triangular with a rounded base and strongly toothed edges. Seed capsules are flat, rounded discs which, when completely dried and after the seeds have gone, are popular for flower-arranging or Christmas decoration.
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Common Dame's-violet Hesperis matronalis
Introduced as a garden plant and occasionally escaping into rough, grassy areas and roadsides, though much less common than the similar Annual Honesty. Flowers May to July. Flowers heavily scented, mauve or white, with the two colours rarely growing together. Leaves spear-shaped with lightly toothed edges. Seed capsules long, thin and held erect.
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Horse-radish Armoracia rusticana
Originally introduced as a culinary plant and now widespread in all kinds of waste places and grassy verges. Flowers May to August. The tough, dock-like, basal leaves are distinctive once known and can form quite extensive patches as the plant spreads by creeping root systems. Flowering shoots are taller than the basal leaves and have narrow, strap-like leaves on their stems.
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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 that 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 capsules long, linear and upright. When in full flower, the violet (not yellow) anthers are very distinctive.
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Tower Mustard Turrita glabra
A Nationally Scarce species, in our area more or less confined to Breckland, where it occurs on a few sandy, grass heaths. One or two plants are known from a small handful of other localities elsewhere. Flowers May to July. A distinctive plant, forming a leaf rosette in the first year, then pushing up a tall, slender flower spike in the second year. Flowers are small but relatively showy due to the tall, slender appearance of the plant. The entire plant is blue-green, waxy and hairless. Seed capsules are long and slender and carried close to the main stem.
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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 capsules 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.
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Common Radish Raphanus sativus
Introduced. Occasionally grown as an arable cover crop in a mixture with other brassicas and sometimes found as a relic of cultivation along field edges. Flowers throughout much of the year, depending on sowing time. Flowers white or whitish with reddish veins, but the pink, red or purple colour can extend variably across much of the petal. Basal leaves rough with coarse, uneven lobes. Seed capsule more or less rounded with a smooth outline, showing little or no constriction between the seeds.
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Common Sea Kale Crambe maritima
Native. Abundant on shingle beaches along much of the Suffolk coast but almost absent from Norfolk except for a small area of The Wash. Flowers May to June. Easily recognised by it thick, waxy, cabbage-like leaves.
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Greater Sea Kale Crambe cordifolia
Introduced from the Caucasus and grown as a garden ornamental in municipal parks, where there is space for its large size. Rarely found as an escape from cultivation along the Norfolk coast. Flowers May to June. Forms clumps of large, crinkly leaves with a massive, spreading head of tiny, white flowers. Very imposing when the huge flower panicle grows up to two metres high.
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Abyssinian Kale Crambe hispanica ssp. abyssinica
(Ethiopian Mustard) Introduced from East Africa as a culinary plant. Occasionally grown on allotments, from where plants were noted spreading at Sheringham, Norfolk recently. Flowers May to August. A spreading plant, to one metre in height, but often much shorter. Stems typically lightly bristly.
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Hoary Alison Berteroa incana
Introduced from Europe. Rare in our region but long established in one or two locations in the Breckland area. Flowers June to August. A slender plant, growing to 60cm but often shorter. The whole plant is covered in dense, star-shaped hairs.
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