Fertile, well-drained soil, or use containers.
Full sun to partial shade.
Limited. Lobelia can take cool weather but is easily damaged by frost.
Mix a standard application of a balanced organic fertilizer into the soil prior to planting. In midsummer, drench plants with a liquid plant food to stimulate new growth.
Alyssum. Lobelia varieties that bloom blue are wonderful cascading flowers to combine with petunias or other easy annuals in containers. You also can use lobelia to edge beds because of its small size.
Single Plants: 5″ (15cm) each way (minimum)
Rows: 5″ (15cm) with 5″ (15cm) row gap (minimum)
Sow and Plant
Sow tiny lobelia seeds indoors, on top of moist seed starting mix, and provide very bright light. Most gardeners buy lobelia seedlings, which are widely available as bedding plants in spring.
Lobelia is a great cool-season flower for adding vivid blue to the garden. Some varieties bloom white or pink.
In early summer, pinch back plants to stimulate the growth of new blossom-bearing branches.
High heat can cause lobelia to suffer, but the plants stay in bloom for many weeks in climates with cool nights.