Peas with Odd Leaves
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. Some have leaves made up of a single blade, but which may look trifoliate due to enlarged stipules at the base of the leaf stalk. In some instances, the leaves may even become reduced to simply tendrils, in which case, the enlarged stipules function as leaves in photosynthesising. This group of plants consists of species that are mostly short annuals.
Where are they found?
The majority of these plants are uncommon, largely introduced species, so may typically be found in man-made or seminatural environments such as gardens, urban areas, rough ground and other disturbed locations.
Identification
Most species can readily be identified by a combination of flower colour and leaf shape.
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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Yellow Vetchling Lathyrus aphaca
Occurs both as a rare native of chalky grass banks or on the Suffolk boulder clay, or as an introduction from southern Europe. Flowers July to August. A small annual plant with leaves reduced simply to tendrils. However, the leaf stipules are much enlarged and create the impression of spear-shaped leaves, pressed against the main stem. The flowers are typically bright yellow on native plants, but introduced plants may have cream-coloured flowers.
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Winged Vetchling Lathyrus ochrus
Introduced from southern Europe. A rare annual species that has been reported from Cambridgeshire Flowers July to August. A small annual with rather peculiar leaves. The midrib and stalk of the leaf is broadened out into a flat blade. The leaf then has a single pair of opposite leaflets toward the top of the leaf, accompanied by a terminal tendril. The flowers are very pale, creamy-yellow in colour.
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Annual Scorpion-vetch Coronilla scorpioides
Introduced from southern Europe. A rare, casual plant, recorded in the region less than five times. Flowers July to August. A small annual plant with simple, ovate leaves, the leaves having enlarged stipules that create the impression of a trifoliate leaf. Small yellow flowers are followed by segmented seed pods that have a 'scorpion-tail' tip to them.
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Caterpillar-plant Scorpiurus muricatus
Introduced from southern Europe. A rare, casual plant, recorded in the region less than five times. Flowers July to August. A small annual plant with simple, ovate leaves, the leaves having narrow, pointed stipules. The flowers are followed by twisted and coiled, spiny seed pods that fancifully look somewhat like little caterpillars.
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Peanut Arachis hypogaea
Native to South America but widely grown in warmer regions of the world as a crop, especially in southern North America and parts of Africa. Commonly used as birdfood but only rarely found germinating as our climate is generally too cool. Flowers July to August. In our region, plants rarely reach the flowering stage and are most likely to be found as small plantlets with just a few leaves. Also known as Groundnut or Monkeynut (especially when seeds are still in their hardened pod). The flowers appear just above ground level and, after fertilisation, grow down into the soil, where the nuts develop below ground.
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