Edging lobelia is best know for cultivars with bright blue blossoms.
Edging lobelia cultivar 'Sapphire' is a favorite for container plantings.
The edging lobelias are a group of different cultivars selected from a plant that grows in South Africa. You aren't likely to see the wild form in cultivation, but there are dozens of outstanding cultivars available. Edging lobelias are low growing perennials that are typically grown as annuals. Some kinds trail along the ground (or over the edge of a container) on weak stems up to 12-18 in (30-45 cm) long. Others are compact, staying just a few inches wide. All have alternate, linear to ovate, toothed leaves about a half inch (12 mm) long, sometimes tinged with bronze or maroon. The flowers are tubular, with two expanded lips. The upper lip spreads out into two erect lobes and the lower lip sports three more or less horizontal fan shaped lobes. Each flower is about a half inch (12 mm) across and several are borne in a loose terminal raceme about 2 in (5 cm) long. The flowers can bloom for months in the spring and again in the fall, and there are many colors to choose from.
The Cascade Series of cultivars are cascading, especially effective in hanging baskets, and come in flower colors including bright red, violet, blue, pink and white. The Rainbow Series are short (4-6 in; 10-15 cm) plants best for edging and flower garden borders. The Moon Series have white, blue, and two-tone blue and white flowers. The Regatta Series start flowering very early and bloom over a longer period with pink, red, blue or white flowers. Cultivars with white flowers include 'Alba', which is compact growing, and 'White Cascade', which has a trailing habit. 'Cambridge Blue' has pale baby blue flowers; 'Crystal Palace' is very dwarf and densely branched with tiny leaves and profuse electric blue flowers; 'Pink Flamingo' has bright pink flowers and grows more upright and branches more than most; 'Rosamund' has bright red flowers; 'Sapphire' is a trailer bearing bright blue flowers with white throats; and 'Kathleen Mallard' has double flowers of blue. There are many more!
Location Lobelia erinus is native to the Cape Province of South Africa. It was introduced to the gardening world, first in Holland, in the late 1600s.
Culture Light: : Site the edging lobelias in full sun in cooler climes and partial shade in zones 7 and above. Potted plants need bright light. Moisture: Edging lobelia is not at all drought tolerant. Water regularly, but be sure the soil or potting medium has good drainage.
Hardiness: USDA Zones 10 - 11. Edging lobelia is a perennial in frost-free climates. Everywhere else we grow it as an annual. It does not tolerate frosts and it suffers during hot summers. Propagation:
Plant seeds indoors 8-12 weeks before the last frost. Don't cover the seeds with the growing mix since they need light to germinate. Just press them into the surface. Edging lobelias also can be divided and cut stems can be rooted to propagate more plants. Most gardeners buy edging lobelia in flats each year as one would petunias or pansies.
Use common lobelia in beds, borders and containers to add brilliant color all season long.
Edging lobelias are used for edging, window boxes, outdoor or patio containers, hanging baskets, and annual flower beds. When in bloom the profusion of (often) brilliant bright blue flowers can be electrifying. Outside, they are great in spring but can succumb to summer's heat, especially if they get too much sun. Pinch back young plants to encourage branching. Cut back to half their height after flowering in summer and you will get another flush of blooms when temperatures moderate. Edging lobelia seems to be ignored by deer and bunnies.
The 370 or so species of Lobelia include annuals, perennials, shrubs, trees and aquatics occurring worldwide. Some authorities place the lobelias in their own family, the Lobeliaceae.
Cardinal flower (L. cardinalis) is a favorite North American wildflower that stands 3 ft (1 m) high and flashes fire engine red flowers at passing hummingbirds.
Contact with the milky sap could cause skin irritation.