Lobelia

Name: Lobelia, Lobelia Erinus, edging Lobelia, Lobelia Cardinalis, cardinal flower.

Height: Annuals usually 10–20cm tall; perennials and shrubs usually 60cm to 1.5m tall.

Foliage: Small oval or lance-shaped green leaves.

Climate: Can be grown in both cool and warm temperate climates.

Soil: Requires a moist, but well-drained, rich organic soil.

Position: Most Lobelias will grow in full sun or partial shade.

Flowering: Tiny colourful two-lipped flowers that repeatedly bloom, from spring until the first frosts. 

Feeding: Use a controlled-release fertilizer when planting. Containerized plants may require a water-soluble fertilizer every month.

Watering: requires constantly moist soil and does not like to dry out. Ensure that you water frequently during the hot summer months.

Characteristics of Lobelia

These are usually seen edging borders or spilling over the edge of pots, containers or hanging baskets. However, there are also upright or clump-forming tall perennials and shrubs suitable for growing in damp borders or by the waterside.

Lobelia originates mainly from the temperate regions of the Americas and Africa, with some perennial species indigenous to Australia. They usually form low mounds covered in flowers, or clumps or rosettes of foliage with upright spikes of two-lipped flowers, in shades of blue, purple, red, pink and white. Most species can be easily grown throughout the temperate areas of Australia and New Zealand. They should be positioned in full sun or partial shade, with protection from the hot afternoon sun in warmer areas. Annual Lobelia varieties will survive light frosts, but will be killed by the first hard frost. Some of the perennial species will grow in the tropical regions, and others in the cold mountainous regions of Australia.

How and when to prune Lobelia

Always pinch out the young growing tips of annual Lobelia seedlings when they are around 2–3cm high to induce bushiness and to produce more flowers. They will take a little longer to flower, but it will be worth it, resulting in increased numbers and a more compact overall shape. 

Prune after the first flush of flowers to encourage fresh regrowth and flowering. 

For most herbaceous varieties, deadhead the main flowering spikes to encourage further flowers, and cut stems down to the base in winter.