These familiar annuals have intensely coloured flowers. They are sometimes listed as Edging Lobelia. They work very well as filler plants in window boxes, hanging baskets, and garden borders. The vivid blue flowers are highly attractive to butterflies and other pollinators. Continue reading below for some expert advice on how to grow Lobelia from seed.
Season & Zone
Exposure: Full sun to partial shade
Sow indoors 6-8 weeks before planting out, and do not plant out until nighttime temperatures are reliably 10°C (50°F) or warmer. On the coast this means sowing indoors around in early April, and planting out in late May. Starting indoors is highly recommended.
Sow on the surface of sterilized seed starting mix. Do not cover the dust-like seeds. Do what you can to sow them evenly on the soil. Provide bright light and a soil temperature of 18-25°C (65-75°F). Germination takes 15-21 days. Water with a mist sprayer. Consider starting Lobelia in 12- or 24-cell plug inserts. It is nice to be able to pull apart clumps of Lobelia for later transplanting. Smaller cell inserts work alright too, but the seedlings tend to grow together in mats, so pulling them apart will cause some loss.