The term “sweet pea” refers to a popular, fragrant flowering vine cherished for its delicate blooms and wide range of colors. Confusion arises because the name is applied to two distinct plants with very different life cycles. The highly sought-after, intensely scented garden flower planted each year is an annual. However, a separate, related species is a true perennial that reliably returns.
The Key Distinction: Annual vs. Perennial Sweet Peas
The common, fragrant garden sweet pea is an annual species, scientifically known as Lathyrus odoratus. The species name itself hints at its most desirable quality—its strong, sweet aroma. It must be replanted from seed annually.
The other plant often called sweet pea is the perennial or everlasting pea, Lathyrus latifolius. This perennial returns from its root system each spring, requiring only one initial planting. While it produces similar-looking flowers, L. latifolius generally lacks the powerful fragrance of the annual variety. Most commercial seeds sold simply as “Sweet Pea” are the annual, highly scented type.
Cultivating the Common Annual Sweet Pea
The annual sweet pea, Lathyrus odoratus, is a cool-season plant that performs best when planted early, either in late fall in mild climates or very early spring as soon as the soil is workable. The plant requires a location with full sun exposure for optimal flowering, but it prefers its roots to remain cool and moist. Gardeners often achieve this by applying a thick layer of mulch or planting low-growing annuals at the base of the vines to shade the soil.
Preparing a rich, well-draining planting site is beneficial, often by amending the soil with generous amounts of compost or well-rotted manure to a depth of about 18 inches. To encourage faster germination, many gardeners choose to scarify the seeds by lightly nicking the hard outer shell or soaking them in water for 24 hours before planting. As a climbing vine, the plant needs vertical support, such as a trellis or netting, which should be placed at the time of planting to prevent later root disturbance.
The process of deadheading, or removing spent blooms, is an important maintenance task for this annual flower. Preventing the plant from setting seed directs its energy back into producing more flowers, which significantly extends the blooming season. The life cycle concludes with the onset of hot summer temperatures or the first hard frost in autumn.
Introducing the Perennial Everlasting Pea (Lathyrus latifolius)
The perennial everlasting pea, Lathyrus latifolius, offers a durable, low-maintenance option for gardeners seeking a permanent vine. This species is hardy, thriving reliably in many regions, often surviving harsh winters. The flowers are typically smaller than the modern annual cultivars and are primarily grown for their visual appeal rather than any strong scent.
This vine is a vigorous climber, reaching heights of six to ten feet, and it requires a strong support structure to accommodate its dense growth. Once established, the perennial pea is quite resilient and can tolerate some drought, unlike its annual counterpart, which prefers consistent moisture. Due to its hardiness and ability to spread by rhizomes and self-seed, it can sometimes become weedy if not managed in the garden.
The perennial type is a robust choice for covering fences or providing background foliage, as it reliably emerges each spring with minimal care. The everlasting pea dies back to the ground in the fall and resumes growth in the spring.