The common name “sweet pea” refers to two different plants, and while both are scientifically classified as legumes, their uses and safety are vastly different. The confusion arises because the term can describe the familiar, edible garden pea or a distinct, highly fragrant ornamental flower. It is accurate to say that all sweet peas are legumes, but this botanical grouping includes one species cultivated for its nutritional value and another that is toxic if ingested. This ambiguity is important to resolve for both gardeners and consumers.
Defining the Legume Family
The classification that unites these two distinct plants is the Fabaceae family, commonly known as the legume or pea family. Plants belonging to this large group are primarily characterized by their fruit, which is a simple dry pod called a legume. This pod opens along two seams to release its seeds when mature.
A defining biological trait of most Fabaceae members is their symbiotic relationship with Rhizobium bacteria, which live in root nodules and perform nitrogen fixation. This process converts atmospheric nitrogen into a form usable by the plant, enriching the soil. Both the edible pea and the ornamental sweet pea share this family characteristic.
The Edible Sweet Pea
The edible sweet pea is the garden pea, scientifically known as Pisum sativum. This species is grown globally for its seeds and pods, which are a valuable food source consumed both fresh and dried. The common forms, such as shelling peas, snap peas, and snow peas, are all varieties of this single, safe-to-eat species.
The nutritional composition of Pisum sativum makes it a beneficial component of a healthy diet. Peas are an excellent source of plant-based protein and provide a substantial amount of dietary fiber, which supports digestive health. Furthermore, peas are rich in micronutrients, including vitamin K, vitamin C, and high levels of B vitamins.
The Ornamental Sweet Pea
The plant primarily known for its beautiful, intensely fragrant blossoms is the ornamental sweet pea, Lathyrus odoratus. While it produces pods that look similar to the edible garden pea, this species is not meant for consumption and is classified as a toxic plant. Its use is strictly for aesthetic purposes in gardens, where it is prized for its climbing habit and colorful, butterfly-shaped flowers.
The toxicity is concentrated in the seeds and pods, which contain a compound called beta-aminopropionitrile (BAPN). Ingesting these parts in large quantities or over a prolonged period can lead to a debilitating condition called lathyrism. This toxin interferes with the formation of cross-links in collagen and elastin, damaging connective tissues. Specifically, this can cause osteolathyrism, which weakens bones, and angiolathyrism, which affects blood vessels, making it unsafe for humans and animals to consume.