Yellow Vetchling

Appearance

"Lathyrus aphaca", known as the yellow pea or yellow vetchling, is an annual species in the family Fabaceae. Plants grow to about 100 cm tall, are pale green to glaucous, glabrous, and have angled but unwinged stems. The leaves are reduced to simple tendrils and what look like leaves are actually stipules, which are ovate-hastate in shape and up to 50 mm long. The flowers are usually solitary and yellow, 10–13 mm in length, and held on long stalks branching from the leaf axils. The flowers, which are bisexual, have 10 stamens and 1 style. "Lathyrus aphaca" is diploid, with 14 chromosomes.

Distribution

It is believed to have evolved in the Middle East, around Syria and Jordan, along with other leguminous species which have a centre of diversity in that region. Edible species of pea were first cultivated in the Fertile Crescent, while weeds such as "L. aphaca" are believed to have adapted naturally to an arable or similar human-disturbed habitat between about 23,000 and 11,000 years ago. "Lathyrus aphaca" itself has some advantages as a farmland weed, being able to fix nitrogen and thus help to fertilise the soil, as well as being edible in small quantities if present in the grain harvest, although it is narcotic when consumed in larger amounts.

Habitat

The native habitat of "L. aphaca" is most likely to be the dry, limestone scrubland in the Middle East sometimes known as phrygana or garrigue. In these countries it is found in both wild and cultivated habitats. It can be an aggressive agricultural weed, infesting mainly wheat, but also other crops, such as sugarcane in Pakistan. The expansion of farming over the last 10,000 years allowed "L. aphaca" to increase its range to southern Asia, as far as Bangladesh, and southern Europe as far as Portugal and even the Azores. In these regions it is often considered native, but it is more likely that it is an ancient introduction, or archaeophyte, which has found a natural or semi-natural analogue of its phrygana habitat, where it can persist in the wild. In Portugal it is considered native only in the Calcareous Western Centre biome, despite being present throughout the country as an agricultural weed. It is more likely that it is a well-established archaeophyte there.

In northern Europe, "L. aphaca" has not generally found any semi-natural analogue of its native arid scrub habitat. In Poland it is described as occurring ‘in a different type of habitats, e.g. in the vegetation of forest edges representing the "Trifolio-Geranietea sanguinei" class, on dry lawns, transport route edges, in orchards, arable fields and fallows.'
Since the early 20th century, it has gone into decline throughout Europe due to improved seed cleaning techniques, and it has largely been eradicated from cereal crops. In the Netherlands, it has declined by 75-100% since 1950, and in Germany and Poland there is a similar story. Meanwhile, however, it has become established as an agricultural weed further afield, in the United States, South Africa and Australia.