How to Grow Sweet Peas

The modern sweet pea, Lathyrus odoratus, is descended from the wild sweet pea of Sicily whose scent, more than its flowers, enchanted Britain when it arrived there in 1699. Since then, many of the plant breeders' improvements have resulted in larger, showier blossoms but loss of strong fragrance. In recent years, though, seedsmen have reintroduced many antique varieties, so you may choose whether the visual or olfactory show is more important. Breeders are now working on combining large flowers and strong scent.

The sweet pea is by nature a climber, using its tendrils to scramble up trellises, canes, netting, fences, and practically anything else vertical to a height of 6 feet in most places, even 9 in a climate it really loves. There are also bush types, ranging in size from 12 inches to 3 feet, most of them suited for containers. The multi-award winning 'Snoopea' tops out at about 2 feet, has no tendrils, needs no support, and blooms generously. 'Explorer' grows only 14 inches tall and is said to be very free flowering.

The sweet pea color range is enormous, incorporating practically every hue except true yellow and true blue. The variety 'Matucana' is very close to the original Sicilian wildflower, with small lavender and purple flowers and a strong perfume. 'Painted Lady' is a 1737 rose and cream sport of the original with a sweet scent. 'Old Spice' comes in a nice color range and also has good fragrance. 'Rosemary Verey', a Thompson & Morgan introduction, is a lovely blend of pink shades with nice perfume.

Getting started

The key to growing sweet peas successfully is soil preparation -- dig very deeply, at least a foot, and add lavish amounts of manure. They languish in hot weather, so in warm climates, such as in California or the lower southern states, plant sweet pea seeds fall through late winter for early spring bloom. In cold zones, it's much wiser to do your soil preparation in the fall, partly because sweet peas need to be planted so early that the deep frost may not be fully out of the ground. You can either start seeds indoors -- in deep containers to prevent root disturbance at transplanting -- or plant them outside about 2 inches deep as soon as the ground thaws in spring. Either way, soaking the seeds for 24 hours before planting or filing them a bit speeds germination, which takes about two weeks outside but happens much quicker indoors with bottom heat. Slugs love sweet peas, so be prepared to fend them off your seedlings. And pinching out the tips when the sweet peas are 4 or 5 inches high will give you more stems and a stronger plant.

Culture

Like clematis, sweet peas prefer their heads in the sun and their feet in the shade, especially in summer, so letting them shelter behind squash or beans is a good idea. Give them almost any vertical structure to climb, so long as it's suited for twining tendrils. Regular moisture is also a necessity, as is, delightfully, regular cutting of the flowers. If you're too tender-hearted to cut a single prized sweet pea, you'll convince the plant it's time to set seed and await the next generation.