Lobelia shares the top spot with Alyssum as Britain’s favourite edging plant, yet it is more demanding than many less-well-known. To provide an impressive and long-lasting show of it needs humus-enriched soil, occasional and a thorough soaking when the weather is dry. To induce bushiness pinch out the tops when the are 1 in. high, and transplant as small rather than singly.
VARIETIES: You will see the Edging Lobelia (L. erinus) everywhere, and the ever-popular deep blue one with a white eye is ‘Mrs Clibran Improved’. Try a different colour for a change – ‘Rosamund’ (red), ‘White Gem’ (white), ‘Cambridge Blue’ (light blue) or ‘String of Pearls’ (mixed). In hanging baskets grow the Trailing Lobelia (L. erinus pendula) – ‘Sapphire’ (deep blue) is a good choice and so is ‘Cascade Mixed’.
SITE AND SOIL: Any reasonable garden soil will do, but rich and moist land is preferred. Thrives in sun or light shade.
PLANT DETAILS: Height 4-8 in.
Spacing: 6 in.
Flowering period: June-September.
PROPAGATION: Follow the Half Hardy Annual technique . Plant out when the danger of frost is past.