Profusely blooming lobelia adds color to beds, planters and hanging baskets. Available with blue, pink or red flowers, there are both annual and perennial varieties of this plant. Lobelia tolerates partial shade as well as full sun, so you can grow it in most landscapes. There are low-growing varieties that work well in garden borders, as well as trailing varieties that add interest to hanging baskets. The seeds are slow to germinate, so sow lobelia seeds indoors 10 to 12 weeks before the last expected frost in your area.
Fill a seed-starting tray with potting soil. Water the soil in the tray until it is evenly moist throughout.
Sprinkle the seeds on the surface of the soil. Lobelia seeds are very small, so plant approximately one seed per square inch in the tray. Cover the seeds with a 1/8 inch layer of potting soil.
Place the tray into a plastic bag, which helps retain moisture in the potting soil during germination. Set the tray in a 70 to 75 degree F room to germinate.
Remove the plastic once sprouts appear, usually within three weeks of sowing. Place the tray in a sunny window in a 70 to 75 degree F room. Water the soil as necessary to keep it moist but not soggy.
Transplant the seedlings to individual 3-inch diameter pots once they grow in their second set of leaves. Plant them in the new pots at the same depth they were growing in the tray.