Sowing & Growing

Start the indoor sowing of Lobelia erinus from late winter through late spring, with a flowering period of approximately 16 weeks. These flowers will bloom continuously until the onset of winter. For optimal results, sow early in the year; however, due to the extended flowering duration of Lobelia erinus, they can be sown until late spring, as long as germination occurs at temperatures between 15 to 20°C (60 to 70°F).

To sow, fill a seed tray or pot with damp seed compost, allowing it to soak in water until fully moist, then draining off any excess. Scatter the seeds thinly across the compost surface, aiming for a fine distribution to facilitate easier pricking out later. Optionally, mix the seeds with silver sand for a more even spread. Gently press the seeds into the compost without covering them, as they require light for germination. Maintain a warm environment at 15 to 20°C (60 to 70°F) and ensure constant moisture.

Germination typically takes 10 to 14 days. Once seedlings are large enough (usually after 5 to 6 weeks), transplant them 5cm (2in) apart into trays with potting compost. Transplanting small clumps is preferable to single seedlings.

Before planting outdoors, acclimate the plants to exterior conditions over 2 to 3 weeks. Plant them out when the risk of frost has passed, typically by the end of May, spacing them 15cm (6in) apart due to their spreading nature. Lobelia erinus thrives in a cool environment with partial shade. Prior to planting, enrich the soil with organic matter or a controlled-release fertilizer.

These plants are not fond of hot, dry weather. In midsummer, cut them back by half their height to rejuvenate and encourage bushier growth. Apply fertilizer and water generously. Keep the plants consistently moist; if they dry out and die back, cut them back, and they should produce a second flush of growth.