Are Ornamental Sweet Peas Edible?

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Are Ornamental Sweet Peas Edible?

Ornamental sweet peas are not edible, they are toxic and should not be eaten!

The common sweet pea, Lathyrus odoratus is an ornamental leguminous annual climbing plant which is native to southern Italy, and is grown purely for its very fragrant and colourful flowers.

Sweet peas and edible peas are related, as both belong to the Fabaceae (legume) family, but they are from different genera (plural form of genus).

Sweet peas belong to the genus Lathyrus, which are commonly known as vetchlings, wild peas or pea vines.

Edible peas belong to the Pisum genus, and originated in Ethiopia, the Mediterranean, central Asia, and the Near East. According to the USDA, peas have been used as a food source for approximately 9,500 years, and have been cultivated by humans for 8,500 years.

There are three major groups of edible peas which are commonly grown:

  1. Garden Peas (Pisum sativum)
  2. Snow Peas (Pisum sativum var. macrocarpon)
  3. Sugar Snap Peas (Pisum sativum var. saccharatum)

What Happens if You Eat Sweet Peas?

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Sweet peas produce pods with peas inside them, and these are peas are poisonous, but only present a low toxicity hazard to humans.

From reports of a gardener I spoke to who accidentally ate them, they taste bitter when eaten fresh, but when cooked the bitterness goes away but they don’t have much flavour.

Accidentally eating the peas or the pods will not result in poisoning, but if large quantities of sweet pea seed are consumed for an extended period, from weeks to months, this can result in a very serious condition known as lathyrism.

The sweet pea (Lathyrus odoratus) seeds contain the toxin beta-aminopropionitrile (BAPN), a collagen cross-linking inhibitor that affects the bones and blood vessels.

BAPN causes osteolathyrism, a collagen cross-linking deficiency which affects skeletal development, causing cartilages and bones to grow abnormally, and angiolathyrism, a weakening of the blood vessels due to the lack of collagen cross-linking, leading to  aortic aneurysm and rupture.

bapn
Chemical structure of beta-aminopropionitrile (BAPN), also known as 3-Aminopropanenitrile

The toxin BAPN present in sweet pea (Lathyrus odoratus) does not affect the nervous system.

Another related member of the Lathyrus genus, Lathyrus sativus, also known as Indian pea or grass pea, does affect the nervous system, it contains the toxin 3-N-oxalyl-2,3-diaminopropanoic acid (beta-ODAP) which causes neurolathyrism, a paralysis and muscle atrophy of the lower limbs due to irreversible motor neuron death.

beta-odap
Chemical structure of 3-N-oxalyl-2,3-diaminopropanoic acid (beta-ODAP) , also known as oxalyldiaminopropionic acid (ODAP)

Why would people eat these harmful plants? In third world countries, where there are food shortages, and conditions are so harsh that edible legumes cannot grow, these hardy Lathyrus plants do manage to grow and are eaten out of desperation. Prolonged use leads to serious health issues.

References

  • United States Department of Agriculture, USDA Plant Guide – Pea, (Pisum sativum)
  • North Carolina State University, N.C. Cooperative Extension, Extension Gardener Plant Toolbox – Lathyrus odoratus
  • Queensland Government, Children’s Health Queensland Hospital and Health Service, Poisonous plants – Sweet pea (Lathyrus odoratus)
  • Lathyrism: A neurotoxic disease, Spencer P.S., Schaumburg H.H. (1983)  Neurobehavioral Toxicology and Teratology,  5  (6) , pp. 625-629.
  • Barrow MV, Simpson CF, Miller EJ. Lathyrism: A review. Q Rev Biol. 1974;49:101–128.

Got any gardening questions? Please feel free to add them to the comments below or email them to deep_green@optusnet.com.au if you would like them answered. Make sure to include pictures in your emails if they help explain a garden problem!

2 Comments

  1. Hello, I live in the north west of California where the lathyrus type ‘wild sweet peas’ grow freely ever since I can remember ( 40 years here). Now in the last 5 years or so, we don’t see them as prolifically as before. A friend mentioned that groups of folks now harvest the shoots in large quantities for eating.
    Has anyone else known of this?
    Do you happen to know if this is mildly toxic or not?

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    1. Wild sweet peas are most likely a combination of annual sweet pea (Lathyrus odoratus) and perennial sweet pea (Lathyrus latifolius) growing amongst each other.

      The Plants For A Future database suggests that the leaves of young plants, seedpods and seeds are edible when cooked, but are safe only if eaten in small quantities.

      Looking up authoritative sources, it appears that the seeds are the most toxic, but the toxic compounds are present in lower concentrations throughout the whole plant – “The toxic principle, β-amino proprionitrile (BAPN), occurs in various concentrations among Lathyrus species and is concentrated in the seeds, but is present in the green parts of the plant as well.
      Reference: Konnie H. Plumlee DVM, MS, Dipl ABVT, ACVIM, … Patricia A. Talcott, in Clinical Veterinary Toxicology, 2004

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