Both sweet peas and edible garden peas belong to the vast Fabaceae family, commonly known as the legume or pea family. This shared lineage means they share certain familial characteristics, such as the production of seed pods and the ability to fix nitrogen in the soil through a symbiotic relationship with bacteria. However, they diverge at the genus level. Edible garden peas are classified under the genus Pisum, specifically Pisum sativum. In contrast, sweet peas are classified under the genus Lathyrus, specifically Lathyrus odoratus. This fundamental genetic distinction is the primary reason for their vast differences in use, chemical makeup, and cultivation purpose.
The most critical difference from a human perspective is their intended use. Pisum sativum, the garden pea, is cultivated exclusively as a food crop. Humans consume its seeds (peas), either fresh, frozen, or dried, and sometimes the entire tender pod, as in the case of snow peas (Pisum sativum var. saccharatum) or snap peas. Lathyrus odoratus, the sweet pea, is cultivated exclusively as an ornamental plant. Its value lies in its vibrant, fragrant flowers, which are prized in gardens and for cut floral arrangements. The plant is not grown for consumption.
This difference in use is directly linked to the plants' chemical composition. The seeds and flowers of the ornamental sweet pea (Lathyrus odoratus) are toxic to humans and animals if ingested. They contain a neurotoxin known as β-aminopropionitrile (BAPN) and other compounds which, in sufficient quantities, can lead to a neurological condition called lathyrism, characterized by paralysis and breathing difficulties. Garden peas (Pisum sativum), on the other hand, have been selectively bred over millennia for safe human consumption. They are a nutritious source of vitamins, minerals, protein, and fiber, posing no toxic threat when properly prepared and eaten.
While the plants may look superficially similar in their vegetative state—with compound leaves and trailing vines—key morphological differences are apparent upon closer inspection. Garden pea flowers are typically white, sometimes with purple or pink hues, and are simpler in form. Their pods are fleshy, rounded, and edible when young. Sweet pea flowers are far more showy, larger, and deeply fragrant. They bloom in a wide array of colors including bi-colors, like pink, purple, blue, red, and white. Their pods are distinctly different: they are smaller, hairier, flatter, and inedible. The seeds within sweet pea pods are also typically smaller and often darker than the green, rounded seeds of edible peas.
Both plants are cool-season annuals that climb using tendrils, but their cultivation is optimized for different outcomes. Garden peas are grown for a maximum yield of pods and are often harvested over a relatively short period before hot weather sets in. Sweet peas are grown for a prolonged display of flowers. To encourage continuous blooming, the flowers must be deadheaded regularly to prevent the plant from setting seed. This practice is the opposite of growing garden peas, where the goal is precisely for the plant to set and develop its seeds (the peas) within the pods.
