Culture
Cool weather annual that is best grown in rich, humusy, medium moisture, well-drained soil in full sun. Tolerates some light shade. Compost may be incorporated into the growing area prior to planting. Best performance occurs in cool soils (soil mulch helps) in cool summer climates with good air circulation. Sweet pea can be a challenge to grow well in hot and humid summers where, as temperatures rise, plants will decline rapidly to the point where removal from the garden becomes necessary. Provide even moisture and regular fertilizer throughout the growing season. Avoid overhead watering to the extent possible. In St. Louis, start seed indoors about 6-8 weeks prior to last spring frost date to maximize bloom time. In warm winter areas, seed may be sown in fall or late fall for winter and spring bloom. Avoid planting sweet peas in the same location in consecutive years. Plants may be grown in bushy mounds or as climbers. Climbers need a support structure on which to grow (e.g., trellis net, fence, strings, stakes or bamboo pyramid). Deadhead spent flowers to prolong bloom. Propagate by seed.
Noteworthy Characteristics
Lathyrus odoratus, commonly called sweet pea, is a bushy or climbing annual that features highly fragrant flowers (odoratus meaning fragrant) on winged stems clad with medium to dark green leaflets in pairs. Stems end in tendrils which enable plants to climb. As a vine, it will climb to 6-8’ in a single season. Without support, it grows in a bushy mound to 2.5’ tall. Fragrant keeled flowers bloom in clusters. In St. Louis, flowers will bloom well from spring to early summer before succumbing to hot temperatures. Further north in cool weather summers, bloom will continue throughout summer to fall. Species plants feature purple flowers, but numerous cultivars now provide a large variety of additional flower colors (pink, red, blue, lavender, purple, white and bicolor). Cultivars come in large, intermediate and dwarf sizes.
Genus name comes from the Greek word lathyros for pea or pulse.
Specific epithet means fragrant.
Problems
No serious insect or disease problems Slugs and snails are attracted to young plants. Aphids may appear. Unlike edible vegetable peas (see Pisum sativum), sweet pea fruits are inedible and poisonous to humans.
Uses
Borders or cottage gardens. Sprawl along the ground or twine on support structures. Containers.