Native to the forests and stream margins of southern Africa, edging lobelia is a small plant that punches well above its size. At four to nine inches, it can disappear among taller plants, but its flower output in late spring is extraordinary, covering the plant in small blooms of blue, violet, purple, red, or pink, often with a contrasting eye at the center. Trailing cultivars drape naturally from hanging baskets; upright forms make tidy, colorful edges along paths and beds.

This plant is fundamentally a cool-season performer. It revels in mild springs and begins to struggle as summer temperatures climb, particularly in humid climates. When it starts to look exhausted in midsummer, cutting it back hard usually prompts a second flush of growth and flowers as temperatures ease in fall. Rich, consistently moist soil and regular feeding every two weeks keep it performing. Growing from seed is slow and exacting; buying transplants is the more reliable route for most gardeners.