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.