Many authors claim that Lathyrus nervosus and Lathyrus magellanicus are synonyms for the same plant. In fact, although they are both blue flowered perennial species from South America, they are quite distinct. L. nervosus is not uncommon in cultivation in the UK, and seed is available from several sources.
Lathyrus nervosus occurs over a wide geographical range in Argentina, Chile, Uruguay and into eastern Brazil. Consequently there is significant variation in the growth habit, hardiness and other characteristics of plants from different areas. These differences appear to persist in cultivated plants.
- name : Lathyrus nervosus Lamarck 1788
- chromosome count : 2n = 14
- common name : Lord Anson's Pea
- section : Notolathyrus
- type : evergreen perennial herb
- habit : sprawling
- distribution : widespread in the southern half of South America
- flowers : blue, quite strongly scented
- legume : 60 mm, black
- seed : mottled
- seed count : approximately 40 seeds per gram
Lathyrus nervosus is generally regarded as a short lived perennial, but can live for many years where the conditions suit it. It dislikes excessive winter wet and should be given a situation with good drainage. In the UK it thrives in a cold glasshouse, but can be more temperamental outdoors. Although L. nervosus can be bullied into climbing, the tendrils show little inclination to grasp available supports, and the plant is at its best sprawling over a bank. The foliage is very attractive but prone to powdery mildew, and the plant is very impressive in full flower.
The small seeds have a hard seedcoat, and germinate more quickly if the seedcoat is nicked with a small file prior to sowing. If sown with heat in January or February the plants will flower in their first year, but are better sown in summer when the plants will flower the following year. The seed pod, or legume, is black when ripe, and strongly dehiscent. Seed of Lathyrus nervosus is available from Owl's Acre Sweet Peas.