Lobelia (Lobelia erinus) is an attractive yearly plant which blooms profusely from early summer to the first frost in fall. The plant is available in compact, bushy forms or trailing varieties. Though it’s possible to propagate lobelia from seed, many gardeners prefer immediate shade supplied by young, nursery-grown plants. Lobelia is perennial in U.S. Department of Agriculture plant hardiness zones 10 and 11.
Lobelia is a small plant which generally rises to heights no taller than 10 inches. Bush types spread only five to nine inches, but trailing varieties expand as much as 1 1/2 feet. Although electric blue lobelia has become the most frequent hue, the plant is available in many different colors such as white, pastels of lavender or pink and vibrant purples and browns. The blooms sometimes take a rest during the hottest aspect of summer, returning to full bloom when temperatures drop in fall.
Lobelia is available in a number of cultivars, such as “Blue Moon,” which exhibits dark blue blooms, and “Crystal Palace,” a comfortable number with deep blue blooms and greenish-bronze foliage. “Rosamunde” is one of the few varieties that exhibits bright red blooms, while “Paper Moon” is stunning with pure white blooms. “Sapphire” is a trailing, purple selection, and “Waterfall” is an unusually tall variety at 12 inches, in colours of white, blue and purple.
Lobelia is a fantastic choice for a rock garden or butterfly garden, as several butterfly species are drawn to the sweet nectar and bright colours. Hummingbirds love lobelia in shades of red or bright purple. Lobelia is stunning along a border, as a mass planting in a flower bed, or cascading over the sides of a patio container or window box.
Lobelia thrives in full sunlight but gains from afternoon shade in warm climates. Any sort of well-drained soil is acceptable, such as purple, clay, or acidic soil. Although the plant blooms best in cool weather, in addition, it performs well in spaces with sunny, cool slopes. Lobelia is rarely bothered by pests and disease, but also much moisture may lead to root rot or stem rot. Water at the base of the plant to keep the foliage dry, and allow the soil to dry slightly between waterings. Lobelia gains from application of a general-purpose garden fertilizer every other week throughout the blooming season.