While sweet peas and edible peas share the same family, Fabaceae (the legume or pea family), they belong to entirely different genera. This is the most fundamental botanical distinction. Edible peas, the kind consumed for food, are classified under the genus Pisum, most commonly the species Pisum sativum. This species encompasses all garden peas, including shelling peas, snap peas, and snow peas. In contrast, sweet peas are classified under the genus Lathyrus, specifically Lathyrus odoratus. The difference in genus highlights that they are separate biological entities, much like how lions (Panthera leo) and domestic cats (Felis catus) are both felines but are not the same animal.
The intention behind cultivating these plants is vastly different and is a key factor in their development. Edible peas (Pisum sativum) are an agricultural crop, selectively bred over centuries for the quality, taste, size, and nutritional value of their seeds and pods. The entire plant is grown with the harvest of food as the end goal. Conversely, sweet peas (Lathyrus odoratus) are an ornamental plant, cultivated exclusively for their aesthetic value. They have been selectively bred to enhance their vibrant and diverse flower colors, their powerful and delightful fragrance, and their performance as cut flowers or climbing garden plants. Their value is visual and olfactory, not culinary.
This is the most critical difference from a health and safety perspective. The seeds of edible peas are a nutritious food source, rich in protein, carbohydrates, vitamins, and fiber. The seeds of the sweet pea plant, however, are toxic to humans and animals if ingested in sufficient quantities. They contain a compound called β-(γ-L-glutamyl)-aminopropionitrile, which, along with other amino acid derivatives, can cause a neurological condition known as lathyrism if consumed regularly or in large amounts. This condition can lead to paralysis, breathing difficulties, and skeletal deformities. While accidental ingestion of a single seed may not cause harm, it is strongly advised to never consume any part of a sweet pea plant.
Upon closer inspection, the plants have distinguishable physical characteristics. Edible pea plants typically have a more compact and bushy growth habit (though some varieties climb), with white or pale flowers. Their pods are fleshy and clearly designed to protect the developing seeds, which are large, green, and starchy when immature. Sweet peas are almost exclusively climbing vines, using tendrils to support themselves. Their flowers are far more showy, larger, and come in a wide array of colors including purple, pink, red, and white, and are highly fragrant. Their seed pods are thinner, tougher, and hairier compared to edible pea pods. The mature seeds themselves are smaller, darker, often brownish or gray, and resemble small, pebbly pebbles, unlike the plump, green peas we eat.
