Lobelia (Half Hardy)


The low growing and trailing forms of this classic bedding plant (such as L. Erinus) are mainly used as border edging or in containers and hanging baskets. In summer its small green leaves are cloaked with masses of tiny brightly coloured flowers, ranging from classic blue too shades of white and pink. If kept watered and well fed, they will provide a good show all summer long.

It should be noted that perennial forms, such as L. cardinalis (Cardinal flower), bare little resemblance to their tender cousins. These are more upright plants, have tall flower spikes rising above clusters of long thin leaves. For details see Perennial Lobelia.

Family: Campanulaceae (bellflower family)
Botanical Name: Lobelia

Foliage: Tender forms have simple, green, alternate leaves. Perennial forms have longer leaves in shades of green or purple.

Flowers: Masses of tiny 2-lipped flowers in shades of blue white, pink, red and purple (depending on variety).

Flowering Period: Mid-summer to early autumn (May to October).

Soil: Moist but well-drained, fertile soil. Sand or loam. Any pH. Do not allow soil to dry out.

Conditions: Best in full sun but will tollerate some light shade.

Habit: Clump/dome forming, low growing and trailing forms.

Type: Half-hardy perennial, usually grown in the UK as a half-hardy annual.

Hardiness: H2 - Half-hardy, protect from frost.

Planting and Growing Lobelia

Grow in deep, rich, moist soil, in full sun or partial shade. 

Trailing forms are popular in hanging baskets, window boxes and containers. Low growing forms are ideal for the front of beds and borders, where a quick splash of colour is needed. All forms flower constantly throughout the summer until the first frosts.

Suitable for any garden type.

Taking Care of Lobelia

To ensure constant flowering, water regularly and feed every week with a high-potash fertilizer or liquid tomato feed. Apply a balanced fertilizer every few weeks. Keep the soil moist, especially in baskets and containers.


Cut back after flowering.

Pests and Diseases

Susceptible to slugs and snails. Damping Off and root rot can cause problems. May also suffer from fungal diseases.

Propagating Lobelia

Sow seed in late winter or early spring, under glass, at 16-18°C. Prick out into pots and plant out in late May, once all danger of frosts has passed.

Popular Varieties of Lobelia Erinus Grown in the UK

Most bedding Lobelia are based on L. erinus, available as a trailing plants or as compact bedding plants.

‘Blue Moon’, compact with clear blue flowers. Early flowering.

‘Cambridge Blue’, compact with light blue flowers.

‘Cascade Mixed’, mixed shades in blue, mauve, red and white.

‘Crystal Palace’, compact variety with rich deep blue flowers and bronze coloured foliage.

‘Lilac Fountain’, trailing form with pale lilac pink flowers.

‘Mrs Clibran’, compact form with violet-blue flowers.

‘Red Cascade’, a trailing form with red, white-eyed flowers.

‘Rosamond’, compact form with crimson flowers.

‘Sapphire’, trailing form with glossy deep blue flowers.

‘Snowball’, compact variety with white flowers.

‘String of Pearls’, mixed colours.