Lobelia is a popular plant for partially shady areas of the garden. Lobelia prefers afternoon shade and fertile, moist but well-drained soil with a pH of 5.5-7.0. Lobelia, Lobelia erinus, is an annual that grows from 4 to 10” high by 6-12” wide. It has a fine texture with a spreading form and is a great shade plant.
Lobelia comes in various colors. Purple, white, pink and two-lipped blue blooms that will flower from summer through early autumn. Mid- to dark green leaves are sometimes stained bronze. Place in odd-numbered groups in the part-shade border, at the edge of a container, or where plants cascade over the rim of a rock wall. Good companions include ‘Pictum’ Japanese painted fern, heart-leaved brunnera, ‘Elegans’ Siebold hosta, ‘Mrs. Moon’ lungwort, and lady’s mantle.
Care and Planting of Lobelia
Lobelia should be planted 6-12” apart in late spring. Water soil deeply when it begins to feel dry. You should try to maintain moist but not soggy soil. If using an irrigation system, maintain deep, infrequent waterings and avoid delivering a light sprinkle every day. Apply 2-3” of organic mulch around, but not touching, plants in summer to help retain soil moisture and as it decomposes it will add organic matter to the soil. Deadhead spent blooms to encourage re-blooming. Remove plants just before the first frost or right afterward when foliage is disfigured.
Propagation of Lobelia
Sprinkle seeds over the soil mix and leave exposed to light; do not cover. Thoroughly moisten and keep moist, not soggy, until seeds germinate. Germination occurs in 15-20 days at 70-80 degrees. Transplant 20-25 days after sowing. After transplanting, reduce the temperature to 60-65 degrees.
Rust and slugs are the most common problems that might develop in your plants.
Cultivars of Lobelia
The cultivar ‘Alba’ has white flowers, ‘Blue Moon’ has deep blue flowers, ‘Cobalt Blue’ has cobalt blue blooms, ‘Crystal Palace’ has vibrant bright blue flowers, ‘Pink Flamingo’ is upright with pink flowers, and ‘Sapphire’ has vibrant sapphire blue flowers.