The Lathyrus latifolius, or perennial sweet pea, is a climbing perennial whose native home is in southern Europe and northern Africa. First harvested in the wild off the coast of Sicily, it grows wild in much of the United States and is often seen as a roadside wild flower. This leafy green vine possesses dainty pink, purple, or white flowers that bloom throughout the summer months and provides attractive bunches of flowers for vases and bouquets. In spite of its beauty, the plant is often considered a weed due to its invasive nature and can be found climbing up steps, railings and trellises or covering walls and fences.
The stems of a perennial sweet pea can grow up to 6 feet (about 2m) high, with multiple branches stemming from the base, and it has a limitless spread. The long, bluish-green leaves have wide outgrowths on either side of the base of the leafstalk known as stipules. The flowers bloom from early spring into fall, are long-lasting, and range in color from pink to white with little or no scent. Pruning dead flowers from the vine encourages more summer blooms. The seedpods the plant produces in late summer or early autumn are mildly toxic, and eating them can cause diseases of the nervous system.
The perennial sweet pea plant prefers a soil that is normal to moist and can tolerate some sand and clay loam soils. In fact, these plants can improve the quality of poor soil by fixing the nitrogen levels when planted temporarily. While they prefer full sun, these perennials do well in partial shade and are tolerant to drought. They require proper support in order to reach their full potential, and high winds may damage or harm them. While relocating the plant may be difficult, it should be rotated periodically to prevent infestation of pests and disease.
The perennial sweet pea is easily grown from the seed, and if planted at the proper time of the year, will grow swiftly. The plant tends to be more difficult to grow in the midwestern United States, and growing problems usually occur because seeds are sowed too late or too early. In cold climates, seeds should be planted early in the spring as soon as the ground thaws for maximum results. In warm climates, it is best to plant the seeds in early October to mid November to experience early spring blooms.