Sweet peas (Lathyrus odoratus)

Winning qualities: Their unparalleled fragrance. “The perfume industry has yet to duplicate it naturally,” says Kolla.

Flowers also come in lots of great colors, from pink, coral, red, and burgundy to deep lavender-blue.

Favorite varieties: ‘April in Paris’ (reneesgarden.com) and ‘Blue Danube’ (enchantingsweetpeas.com).

When to plant: February or as soon as the soil can be worked in cold climates; September through January in mild climates (or in early spring, look for seedlings in 4-inch pots at nurseries).

Growing tips: Plant in rows running north to south, or near an east-facing wall; seedlings should be at least 6 inches apart.