How to Grow Lobelia Erinus. With its gorgeous blue or white petals cascading over pots and out of windowboxes, lobelia is the ideal container plant. An annual (it grows just one year), it likes cool conditions and won't bloom if temperatures regularly top 80 degrees. It grows 4-8 inches high and sprawls over the ground or over the sides of containers.
Things You'll Need
- Bypass Pruners
- Compost Makers
- Garden Hoses
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Buy healthy, green plants in spring with no signs of wilting or disease. Plants should be stocky with plenty of leaves. It's actually a plus if they don't have any flower on them so that they'll divert their early energy into root development rather than flowering.
Plant lobelia seedlings in spring, a week or two before your season's last frost date, in a spot where they'll get full sun to very light shade. They appreciate a little afternoon shade.
Work a little compost into the planting soil. Lobelia likes rich soil high in organic matter.
Pinch the ends off the lobelia plants to encourage branching and fuller plants with more flowers.
Keep the soil evenly moist. If planting in a container, it's a good idea to work in some polymer crystals into the soil to help the soil retain water.
Pull out and discard plants once heavy frost kills them in autumn.