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Fabaceae FAMILY

Lathyrus japonicus

Lathyrus japonicus

Edibility
2/5
Medicinal
0/5

Safety & Hazards

All parts of the plant, but especially the seed, contain a toxic amino-acid. It is produced in the plant at about the same time that the seed starts to develop. In small quantities the amino acid is innocuous, and the seeds of several Lathyrus species are eaten as a nutritious part of the diet. However, in larger quantities (the seed should form less than 30% of a balanced diet), it can cause a very serious disease of the nervous system known as 'lathyrism'. Symptoms appear as a paralysis of the muscles below the knees, pains in the back, followed by weakness and stiffness of the legs and progressive locomotive incoordination[1, 2, 3].

Cultivation Details

HabitPerennial
Growth—

Lathyrus japonicus is a very cold-hardy plant, able to tolerate temperatures down to around -35°c when fully dormant[4]. An easily grown plant, succeeding in any moderately good garden soil[5]. It prefers a deep moist well-drained soil in a cool position[6]. Prefers a position in full sun, growing well on hot sunny banks[4]. The seed remains viable for 4 - 5 years in sea water[4]. This species has a symbiotic relationship with certain soil bacteria, these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby[4].

Propagation

Pre-soak the seed for 24 hours in warm water and then sow in early spring in a cold frame[4]. When they are large enough to handle, prick the seedlings out into individual pots and plant them out in the summer. If you have sufficient seed, then it can also be sown in situ in mid spring[4]. Division in spring. It may not transplant well so care should be taken[4]. Cite as: Temperate Plants Database, Ken Fern. temperate.theferns.info. 2026-02-21. <temperate.theferns.info/plant/Lathyrus+japonicus>

Pollinators

Bees, Lepidoptera

References

  1. [1]A Colour Atlas of Poisonous Plants. — Frohne. D. and Pfänder. J. · Wolfe · 1984 · ISBN 0723408394 ↩︎Brilliant. Goes into technical details but in a very readable way. The best work on the subject that I've come across so far.
  2. [2]Poisonous Plants in Britain and their Effects on Animals and Man. — Cooper. M. and Johnson. A. · HMSO · 1984 · ISBN 0112425291 ↩︎Concentrates mainly on the effects of poisonous plants to livestock.
  3. [3]The Leguminosae; A Source Book of Characteristics, Uses and Nodulation — Allen O.N.; Allen E.K. · University of Wisconsin · 1981 · ISBN 0-333-32221-5 ↩︎An amazing and comprehensive work, giving a brief guide to the many genera of the family Fabaceae and also the principle uses of the genus.
  4. [4]The New RHS Dictionary of Gardening. 1992. — Huxley. A. · MacMillan Press · 1992 · ISBN 0-333-47494-5 ↩︎Excellent and very comprehensive, though it contains a number of silly mistakes. Readable yet also very detailed.
  5. [5]RHS Dictionary of Plants plus Supplement. 1956 — F. Chittendon. · Oxford University Press · 1951 · ISBN - ↩︎Comprehensive listing of species and how to grow them. Somewhat outdated, it has been replaced in 1992 by a new dictionary (see [ 200 ]).
  6. [6]Perennials. Volumes 1 and 2. — Phillips. R. & Rix. M. · Pan Books · 1991 · ISBN 0-330-30936-9 ↩︎Photographs of over 3,000 species and cultivars of ornamental plants together with brief cultivation notes, details of habitat etc.
  7. [7]Vascular Plants of the Pacific Northwest. — Hitchcock. C. L. · University of Washington Press · 1955 · ISBN - ↩︎A standard flora for Western N. America with lots of information on habitat etc. Five large volumes, it is not for the casual reader.
  8. [8]The History and Folklore of North American Wild Flowers. — Coffey. T. · Facts on File. · 1993 · ISBN 0-8160-2624-6 ↩︎A nice read, lots of information on plant uses.
  9. [9]CosIng — http://ec.europa.eu/growth/tools-databases/cosing/ ↩︎CosIng is the European Commission database for information on cosmetic substances and ingredients.