Lobelia plant performs best with full sun to partial shade and rich, well-draining soil. Choose a site that receives at least 4-6 hours of direct sun. Follow these steps and space garden lobelia plants 6-18 inches apart, depending on the variety.
Soil: Lobelia prefers rich, well-amended soil with a slightly acidic pH between 6.0 and 7.0. Mulch with a layer of compost to add nutrients, suppress weeds and retain moisture. For containers, use a high-quality all-purpose planting Mix.
Watering: Keep lobelia evenly moist but not soggy. Overwatering may cause root rot or other diseases. Water regularly during extreme heat or prolonged dry spells. Too little water can cause plant stress, stunted growth, and fewer flowers or brown foliage.