ESSEX BOTANY AND MYCOLOGY GROUPS
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ESSEX BOTANY AND MYCOLOGY GROUPS |
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Lathyrus aphaca:
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__________________________________________________________________________________ Lathyrus aphaca L. Yellow Vetchling __________________________________________________________________________________
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This species is suspected of being a long established introduction, originally with arable crops, but is now well established in Essex on well drained calcareous, chalky, sandy or alluvial soils in thermophilic sites on verges, by hedges, on waste ground and in disturbed grassland. Nationally, it is largely confined to southern England, with scattered casual records north to the Scottish lowlands. The bulk of its past and present distribution however appears to coincide with an area enjoying a mean July temperature in excess of 17oC (62oF) and a mean February temperature in excess of 1.5oC (35oF) during the period 1901-1930. It has been recorded from c.100 UK hectads since 1987 (BSBI Atlas 2009). Being a southern European and Asiatic winter-green annual, its seeds germinate in the autumn, and I have lost seedlings in the winter frosts. Its UK distribution suggests therefore that apart from scattered casual, ephemeral germinations elsewhere, its stronghold populations depend on the temperature holding above a mean of 1.5oC (35oF) in February and getting warm enough in summer for it to out-compete or scramble over other grassland species. Even in Essex it only seems to persist in sheltered pockets, very often on south facing slopes on chalky or alluvial soils. It seems to need disturbance and can be present in dense patches in recently disturbed grasslands. In India and Pakistan it climbs up and smothers Rice, Wheat and Mustard crops and grows as a contaminant of leguminous crops, which suggests it could well have been a common contaminant of imported clover or tare seed in the past, our present day populations arising from field margin remnants. In Essex it flowers from April to the end of August. In Lahore it has been studied in wheat fields, where it gerrninates November to January, grows vegetatively December to February, flowers February to April, and drops enough seed by the end of April to survive the harvesting of the wheat crop in May. In Essex a population has persisted near Boyton Cross (Chelmsford) for almost 150yrs and it has persisted at Grays Chalk Quarry for 80 yrs. Gibson lists 18 sites, and although we have many more records than those listed in Jermyn 1974, the increase is probably due to better coverage rather than a real increase, although it is said to be spreading rapidly in north west Kent and may therefore be responding to a recent milder climate. In common with other Lathyrus species it has a water impermeable seed coat that enforces dormany, although there is some evidence from Indian studies that there is cyclical opening of the micropile. In cultivation the seed coat needs to be nicked, to allow imbibition, and it will then germinate in 10-20 days in the dark at 70oF. Viability? [Frequently mis-recorded because of confusion with Lathyrus pratensis which frequently has conspicuously large stipules, although retaining its green leaflets, whereas in L. aphaca its distinctive, large, heart-shaped stipules take over the function of its potentially pinnate leaves which are reduced to tendrils from the second leaf stage ]. Post -1930 records:
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Pre-1930 records:
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