Most sweet peas -- vining annual plants with large, yet delicate, heavily perfumed flowers -- do well only in cool spring or summer weather. Perennial sweet peas, a favourite in the Victorian-era cottage gardens of England, Europe and the U.S., are distinctively different. Flowers of perennial sweet peas are smaller and orchid-like, unscented and with a limited colour range of white, lavender-pink and magenta. They also resist drought, thrive in heat and bloom all summer long.
Perennial Sweet Peas
Perennial sweet peas, Lathyrus latifolius, growing wild throughout the West are descendants of popular cottage-garden sweet peas, now naturalised as roadside wildflowers. But they are still widely cultivated, especially by cottage gardeners and others who want a long blooming, delicate yet easy-care summer sweet pea that tolerates heat and drought conditions. Plant seeds from March to May, when soil can be worked, to establish perennial plants. The following year, vigorous vining plants climb trellises, walls and fences or sprawl across bare slopes, abloom with dainty pale pink, rose-coloured and white. Some gardeners use hardy perennial sweet peas to create permanent blooming screens or hedges, as well as to plump up summer bouquets. For longest bloom, irrigate well during hot weather and fertilise regularly.
Perennial Sweet Pea Seeds
Like all other sweet pea varieties, the seeds, pods and other parts of perennial sweet peas are poisonous and should never be eaten. Seeds of perennial sweet peas are protected by a particularly hard seed coat, which prevents seed germination in the absence of ideal conditions. Gardeners use a process known as "seed scarification" to sidestep this limitation. Seed scarification involves softening, scratching or otherwise breaking through the seed coat so water penetrates the seed and initiates germination. Before planting, roll seeds on rough sandpaper to slightly nick their seed coats before planting, or soak seeds in water for 24 hours. Ironically, once established perennial sweet peas will self-sow quite successfully -- creating a large and ever-growing sweet pea patch that requires little care other than regular feeding and watering.
Perennial Sweet Pea Cultivars
In the U.S. the three main cultivars of perennial sweet pea -- also known as everlasting sweet pea -- typically come packaged as a mix or blend, while in the United Kingdom each variety is well known, prized, packaged and sold on its own. Pink Pearl features pale pink flowers veined with deeper pink or lavender pink, an excellent cut flower introduced to English gardens before 1635. Old-fashioned Red Pearl is known for its deep magenta-pink flowers and similarly vigorous vining habit. Honoured with the Royal Horticultural Society Award of Merit, White Pearl is another vigorous climber appreciated for its long-lasting pearly white stems of blooms, perfect cut flowers for summery bouquets.