Height 10-23cm (4-9in)
Planting distance 10cm (4in)
Flowers late spring to autumn
Fertile moisture retentive
Sunny or partially shaded site
Half-hardy perennial grown as an annual
Though grown as an annual, Lobelia erinus is correctly a half-hardy perennial. It is a small plant, only 10-23cm (4-9in) high, with light green leaves, and it produces a mass of small bluefrom late spring until autumn frost.
More popular than the species are the many varieties which may be either compact, making neat 10-15cm (4-6in) high domes, or trailing in a spread of 30cm (1ft) across. The colour range of the varieties embraces white, pale blue, deep purplish-blue and wine-red.
The varieties with a compact habit are normally used to edge beds while those with a trailing habit look effective in hanging baskets, window-boxes and other containers.
The following varieties are readily available.
‘Blue Moon’ is a compact, early-flowering variety. The large flowers are clear blue.
‘Cambridge Blue’ is neat and compact with light blue flowers.
‘Cascade Mixed’ is a mixture of cascading varieties coming in blue, mauve, red and white, usually with white eyes.
‘Crystal Palace’ is a compact variety bearing rich deep blue flowers. The foliage is bronze-coloured.
‘Fountain’ is a trailing variety, with pale lilac-pink flowers. Other strains in this series include white and blue-coloured varieties.
‘Mrs Clibran’ is a compact plant bearing rich violet-blue flowers with white eyes.
‘Red Cascade’ is a trailing variety with wine-red, white-eyed flowers.
‘Rosamund’ is a compact variety bearing crimson flowers with white eyes.
‘Sapphire’ is a trailing variety with white-eyed, glossy deep blue flowers.
‘Snowball’ is a compact variety with white flowers, though some are slightly tinged with blue.
Sow the seeds in late winter in pans of seed compost and keep at a temperature of 16-18°C (61-64°F). Prick out the seedlings in groups of three or four — they’re too small to prick out individually – and grow on at a temperature of 13-16°C (55-61°F). Harden off and plant out in late spring.
Plant lobelia in rich moist soil in a sheltered, sunny or partially shady position.
Pests and diseases
Damping off andcan cause the plants to wilt and stem rot may show as pale spots on the leaves of seedlings.