The sweet pea (Lathyrus odoratus) is an annual flowering plant beloved by gardeners for its intense fragrance and delicate beauty. Native to the Mediterranean region, this climber has been cultivated for centuries, becoming a staple in cottage gardens and floral arrangements. The plant’s specific epithet, odoratus, translates to “fragrant,” highlighting its most celebrated feature. This article explores the sweet pea’s physical traits, details the steps required for successful cultivation, and clarifies the safety distinction between this ornamental plant and its edible namesake.
Defining Characteristics and Types
Sweet peas are identifiable by their distinctive, delicate flowers that resemble butterflies. These blossoms are composed of five petals: a large, upright banner petal, two side wings, and two lower petals that form a keel shape. The colors of Lathyrus odoratus are incredibly diverse, spanning from deep crimson and navy blue to pastel pinks, lavenders, and pure whites.
The plant is a vigorous vining annual, utilizing branched tendrils to grasp and climb available supports, often reaching heights of six to eight feet. Without a support structure, the plant will grow into a more bushy, mounding form, typically reaching about three feet tall. Its most defining sensory trait is the pervasive, sweet scent that can fill a garden.
Gardeners sometimes confuse the annual sweet pea (L. odoratus) with the perennial everlasting pea (Lathyrus latifolius). While the everlasting pea shares the vining habit and general flower shape, its flowers are generally unscented. Choosing between the two often depends on whether the gardener prioritizes the annual’s intense fragrance or the perennial’s ability to return year after year.
Essential Care and Cultivation
Successful growth of sweet peas depends on providing the right conditions, as these plants thrive in cool temperatures and rich soil. Seeds should be sown early, either in late fall in mild climates or in late winter to early spring in cooler regions, about four to six weeks before the last expected frost. To aid germination, the hard seed coat can be softened by soaking the seeds in water for 8 to 24 hours before planting.
The ideal planting location offers full sun exposure and features rich, humusy, and well-drained soil. Sweet peas are heavy feeders and benefit from the incorporation of aged manure or compost into the soil before planting. Since they are cool-weather annuals, they perform best when the soil remains cool, and they will rapidly decline once hot, humid summer weather arrives.
Vining varieties require a sturdy support system, such as a trellis, netting, or stakes, which should be installed before planting. Once the young plant reaches four to six inches, pinching out the central growing tip encourages the plant to branch out, resulting in a bushier habit and a higher yield of flowers.
Consistent and deep watering is necessary, as sweet peas are thirsty plants that will not thrive if their roots dry out. Feeding should focus on promoting blooms rather than excessive green growth, meaning fertilizers should be lower in nitrogen and higher in potash and phosphate.
To extend the flowering season, regularly remove spent blooms, a process called deadheading, or cut the flowers frequently for bouquets. If seed pods are allowed to form, the plant will cease flowering as it completes its reproductive cycle.
Important Safety Note: Sweet Peas vs. Edible Peas
A common point of confusion leads many to question if sweet peas are safe for consumption. The ornamental sweet pea (Lathyrus odoratus) is distinct from the edible garden pea (Pisum sativum). The sweet pea is not meant for eating and is considered toxic if ingested by humans or pets.
The plant contains amino acid derivatives, which are neurotoxins. The highest concentration of these toxic compounds is found within the seeds and the seed pods. Ingestion of large quantities can lead to lathyrism, a condition that affects the nervous and musculoskeletal systems.
The genus difference, Lathyrus versus Pisum, serves as the most accurate distinction between the toxic ornamental plant and the safe vegetable. Gardeners must be mindful of this safety distinction and ensure that sweet peas are not confused with any edible pea varieties.