The sweet pea (Lathyrus odoratus) is an annual flowering plant belonging to the Fabaceae family. It is renowned primarily for producing a spectacular display of blooms accompanied by a powerful, pleasant fragrance.
The Distinctive Flower Structure
The most striking feature of the sweet pea is its irregular, butterfly-like shape, known as papilionaceous. Each bloom is composed of five specialized petals. The uppermost and largest petal is the upright standard, sometimes called the banner, which often flares backward to provide a showy backdrop.
Flanking the central structure are two smaller petals known as the wings, which help to enclose the flower’s reproductive organs. The final two lower petals are fused together to form a boat-shaped structure called the keel. These blooms typically measure between one and three centimeters across and are clustered together on long, sturdy stems.
Sweet peas offer a wide color palette, expanded through hybridization. Common colors include various shades of pink, rose, lavender, purple, white, and bi-colors. A true pure yellow is generally absent in this species.
Vining Habit and Leaf Appearance
The sweet pea grows as a climbing annual vine, though bushier, non-climbing varieties exist. The stems are slender and often exhibit a winged or slightly ridged structure. This detail helps distinguish the plant’s stems from those of other common garden climbers.
The foliage consists of pinnately compound leaves, where each leaf is typically comprised of a pair of dark green leaflets. These leaflets are generally ovate to oblong in shape and arranged alternately along the stem. The plant’s climbing ability is facilitated by a specialized modification of the terminal leaflet.
This modified structure takes the form of a multi-branched tendril. These tendrils actively coil and grasp onto nearby supports, allowing the vine to ascend to heights often reaching six to eight feet in a single season. Following the bloom, small, green, pea-like pods develop, which dry and turn brown as they ripen.
Scent and Safety Considerations
A defining feature of Lathyrus odoratus is its fragrance, which is often described as sweet, sometimes with spicy or honey-like undertones. This strong scent contributes to the plant’s enduring popularity as a garden flower and for use in bouquets. However, the plant’s visual similarity to edible peas requires a strict safety distinction.
The seeds contained within the sweet pea’s pods are not for human or animal consumption. They contain poisonous aminopropionitrile compounds, such as beta-amino-propionitrile (BAPN). Consuming large quantities of the seeds over an extended period can lead to a serious paralytic condition known as lathyrism.
Gardeners must not confuse the ornamental sweet pea (Lathyrus odoratus) with the edible garden pea (Pisum sativum). While the ornamental pods look similar to their edible relatives, they carry a distinct safety risk. Accidental, small-scale ingestion typically results in minor symptoms, but the seeds should be kept away from children and pets.