Edging lobelia

About Edging lobelia

Edging lobelia is a small, mounding or trailing annual covered in tiny flowers, most often in deep blue or violet, often with a white eye. It came from South Africa's Cape and was the favorite blue of Victorian bedding schemes; today it's loved in window boxes, hanging baskets and along bed edges. It likes cool weather and steady moisture, often resting in summer heat and blooming again in fall. It's a cousin of the native cardinal flower, which has its own entry.

Perennial only in zones 10-11 (NC State); everywhere else it's a spring-to-fall annual, best in cool-summer areas. In Florida it's grown in the cool season (UF/IFAS).

When to plant

Timing is counted from your average last spring frost (and first fall frost). Sow & Tell works out the actual dates for your ZIP code.

• Start seeds indoors: 8 to 13 weeks before the last frost
• Set out plants: up to 2 weeks after the last frost

Days to harvest count from sowing: UF/IFAS says plants bloom about four months after seeding. Start seed indoors about 8 weeks before planting out (Arkansas); UMN allows 12-13 weeks indoors. NC State notes it can be tricky from seed, so most gardeners buy plants. Set out after the last frost, since it won't take a late spring freeze (Arkansas); in Florida plant in fall or winter (UF/IFAS).

Soil

Rich, well-drained soil kept evenly moist; it has little drought tolerance but rots if waterlogged, especially in southern heat (NC State, Arkansas, UF/IFAS).

Plant in rich, fertile, well-drained soil with plenty of organic matter (NC State, UF/IFAS).

Feeding

• Every two weeks through the growing season: balanced fertilizer. NC State suggests feeding about every two weeks; Illinois says keep feeding in summer to keep it flowering. Follow the label rate.

Don't overwater: soggy soil in summer heat often rots the roots, especially in the South (Arkansas, NC State).

Harvest

Blooms from late spring into summer and again as fall cools (June to October in Illinois). It often stops flowering in hot weather; shear plants back after each flush to bring on more blooms (NC State, Illinois, UF/IFAS).

Varieties (13)

NC State and UF/IFAS document 13 cultivars and series; few sizes are given.

Diseases and problems

Damping-off, Stem rot, Root rot

In the kitchen

Safety: Poisonous to people (NC State, medium severity): all parts contain lobeline and related alkaloids, and eating large amounts can cause nausea, vomiting, diarrhea, weakness and worse. Colorado State lists Lobelia species among toxic garden plants. Don't eat any part.

Pets: Toxic to dogs, cats and horses (ASPCA): its lobelia entry (cardinal flower, L. cardinalis) lists lobeline, with vomiting, diarrhea, drooling, depression, belly pain and heart rhythm problems. The ASPCA has no separate entry for edging lobelia, but NC State notes it contains the same alkaloids.