Everlasting-peas
What are they?
Members of the pea family are readily told by their distinctive flowers, but they are a very diverse group when it comes to their leaves and other features such as fruits. Most species have pinnate or trifoliate leaves, but the species here are unusual in having rather different leaves. Although these species have a type of pinnate leaf, their leaves have been reduced to just a single pair of leaflets, which may be narrow or broad, while the tip of the leaf is often extended out into a twining tendril that helps the plant to scramble over other vegetation. The stems, too, have been modified and are often broad and flattened. The everlasting-peas get their name because they are perennials that come up year after year, rather than one-year plants (annuals). However, this page also includes the Sweet Pea and related species, since the flowers and leaves are similar to those of everlasting-peas, though they differ in being annuals.
Where are they found?
Quite a number of these species occur naturally in southern Europe and have been introduced to the UK as desirable garden ornamentals or vegetable crops. Such plants may turn up in a variety of grassy places, urban environments or lightly disturbed or cultivated places and the perennial species can become well-established. We do, however, also have one native species, which is scarce in grassy places.
Identification
Sorting out the members of this group can be tricky and attention needs to be paid to details of almost all parts of the plant. You should check for hairiness, whether the stems are winged, the precise details of the leaves and measure the length of the flowers.
Sweet Pea Lathyrus odoratus
Introduced annual from southern Europe. Rarely found as a short-lived plant from dumped garden waste but not persisting. Flowers July to September. A strong climber to 2.5m with slightly hairy, winged stems and well-rounded leaflets. The leaf tendrils are large and many-forked. The flowers are popular for their rich odour and occur in a bewildering array of colours - often bicoloured.
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Culinary Pea Lathyrus oleraceus
Introduced as a vegetable from mainland Europe and widely grown as a field crop. Occasional plants may appear on roadsides or field edges from spilt seed. Flowers July to August. An annual plant with unwinged stems and with remarkably adapted leaves. The leaf itself is reduced to merely a many-branched tendril with no blades, while the role of the leaf has been taken over by the greatly enlarged stipules that sit in pairs alongside the main stem. The flowers of cultivated plants are typically white with green veins, but flowers from wild stock are typically lilac and purple.
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Marsh Pea Lathyrus palustris
Native. A Nationally Scarce species and classified as Near Threatened, in East Anglia confined to well-managed, protected sites in the Broads. Flowers May to July. A scrambling climber, to 1.5metres in tall herb fen vegetation, where it is hard to spot when not in flower. The flowers are bluish-purple, carried in a loose cluster of 2-6, the cluster appearing on the end of a long, slender stalk. Leaves with two to three pairs of narrow, upright leafets and ending in a forked tendril. Leaf stipules broader than the winged stems.
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Bithynian Vetch Vicia bithynica
Introduced from mainland Europe. A rare casual in East Anglia, once quite well established in rough grassland at Felixstowe but the site has been destroyed by development. Flowers May to June. An annual to 60cm, with solitary, bi-coloured flowers and strongly toothed leaf stipules. The leaves have 1-2 pairs of narrow leflets and branched tendrils.
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Hairy Vetchling Lathyrus hirsutus
Introduced from mainland Europe. A rare annual that occasionally appears from discarded garden waste. Flowers May to July. A scrambling climber to one metre in length but often shorter. The flowers are purple with paler, bluish wings, carried in a loose cluster of 1-8, the cluster appearing on the end of a long, slender stalk. Leaves with one pair of narrow, upright leafets and ending in a forked tendril. Most easily told from other peas by its hairy seed pods.
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Bitter-vetch Lathyrus linifolius
(Lathyrus montanus) Though a widespread and fairly common native in the UK, this species is effectively absent from East Anglia, having disappeared from former sites on the edge of our region in Essex, but it may be found again one day. Flowers April to July. Flowers pinkish-purple, becoming suffused with blue as they age. A low species, often forming small tussocks of stems.
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Tuberous Pea Lathyrus tuberosus
Introduced perennial from eastern Europe. Although plants can be long-lived in grassy places, this species seems to have been lost from the handful of sites that it was formerly known from. Flowers July. A weak climber and more a scrambler with hairless, angled but unwinged stems and well-rounded leaflets. The leaf tendrils are forked but relatively small and sometimes absent. Flowers rich, cerise-pink, 2-7 in a cluster, 12-20mm long.
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Broad-leaved Everlasting-pea Lathyrus latifolius
Introduced from mainland Europe and widespread as a garden escape. By far the commonest species of everlasting-pea in the wider countryside. Flowers June to August. A strong-growing perennial, clambering over other vegetation with hairless stems growing to three metres or more in a season. Winged stems, leaflets and stipules all broader than those of the native, Narrow-leaved Everlasting-pea. Leaflets typically less than four times long as wide. Flowers usually bright, rich pink, but may also be white, 15-30mm long and in bunches of 3-12.
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Narrow-leaved Everlasting-pea Lathyrus sylvestris
Rare overall in East Anglia and most frequent in Breckland where it is probably native, with records from elsewhere probably involving garden escapes. Flowers June to August. A scrambling perennial, clambering over other vegetation with hairless stems growing to two metres or so in a season. Winged stems, leaflets and stipules all narrower than those of the introduced Broad-leaved Everlasting-pea. Flowers usually bright, dull, pale pink, 12-20mm long and in bunches of 3-12.
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Variable-leaved Everlasting-pea Lathyrus heterophyllus
Introduced from mainland Europe as a garden plant. Common in the dunes at Burnham Overy, Norfolk, surviving since the 1940s from a long-gone garden. Somewhat bizarrely, for this reason alone, it has been called 'Norfolk Everlasting-pea in some publications! Flowers June to August. A strong-growing perennial, clambering over other vegetation with hairless stems growing to three metres or more in a season. Stems winged, the leaflets typically more than four times long as wide. Flowers bright pink and typically darker-veined; 12-22mm long and in bunches of 3-12.
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Two-flowered Everlasting-pea Lathyrus grandiflorus
A rare introduction from southern Europe but long-persistent in grassy places in a handful of locations. Flowers June to August. A strong-growing perennial, clambering over other vegetation with hairless stems growing to two metres in a season. Unwinged, hairless stems. Leaflets broadly rounded, mostly with branched tendrils. Flowers large, 25-35mm long, in pairs or carried 1-4 in a bunch and usually bi-coloured, bright, rich pink.
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Indian Pea Lathyrus sativus
Introduced annual, native to southern Europe and Asia. Not formally recorded since the 1940s but formerly occurred as a grain contaminent in docks and on tips. Flowers June to August. A weak climber or scrambler with hairless, narrowly winged stems and leaves with one pair of leaflets. The leaf tendrils are branched. Flowers blue, white or pink, solitary, 12-24mm long. Seed pod with two narrow wings along one side.
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