Culture
Nemesias are difficult to grow well in many parts of the U. S. because of their preference for moderate daytime temperatures and cool nights. They detest hot and humid summer conditions. In St. Louis, nemesias are primarily grown as cool weather annuals in humusy, evenly moist, well-drained soils in full sun to part shade. Best performance is in full sun, however these cool weather lovers will bloom longer into the hot St. Louis summer if given some part afternoon shade. When plants do succumb to the hot weather, cut them back for a possible fall bloom or remove them from the garden. Start seeds indoors 8-10 weeks before last frost date or purchase starter plants. Set out seedlings/starter plants at last frost date. Seed should not be sown directly in the ground in spring in the St. Louis climate.
Noteworthy Characteristics
Nemesias are tender perennials, annuals and sub-shrubs that are mostly native to southern Africa. In the U. S., cultivars of Nemesia strumosa (many of which are actually hybrids between N. strumosa and N. versicolor) are commonly grown as flowering cool weather annuals. These plants typically grow to 6-12” tall. Plants have lance-shaped, sometimes toothed, green leaves (to 3” long) in pairs on four-sided stems and two-lipped tubular flowers in short terminal racemes. Each corolla has a pouch or pinched spur at the base. Flower colors include cream, yellow, orange, pink, red, brown, blue (most colors except green) and sometimes bi-color (upper and lower lips of different colors). Flowers bloom spring to fall in northern cool summer climates, but spring to early summer in St. Louis.
Genus name comes from the Greek name nemesion for a similar plant.
Problems
No serious insect or disease problems. Root rot may occur in poorly drained soils.
Uses
Beds, mixed borders, rock gardens or containers.