Lobelia: Growing From Seed, Care and Trailing Varieties

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Lobelia is an annual that covers itself in so many tiny blue, sky-blue, lilac or white flowers that the leaves almost disappear. Bushy varieties form neat cushions along edges, while trailing types cascade from hanging baskets and window boxes. The hardest part is raising seedlings from the dust-like seed — after that, lobelia flowers until autumn. Here is how.

Types and varieties

• Edging lobelia (Lobelia erinus) — the main species for beds and balconies. Bushy varieties ('Riviera', bronze-leaved 'Crystal Palace') grow 10–15 cm tall; trailing ones ('Sapphire', 'Regatta', 'Fountain') cascade 30–40 cm.
• Cardinal flower (L. cardinalis) and L. fulgens — perennials with bright red spikes for damp spots.

Sowing seedlings

1. Sow from late February to mid-March. The seed is dust-fine — use pelleted seed or mix it with dry sand.
2. Scatter it on the surface of moist, light compost without covering, as it needs light. Cover with film and keep at 18–22 °C.
3. Seedlings appear in 1–2 weeks; water from below or with a fine mister.
4. Prick out in small clumps of 3–5 seedlings rather than singly.
5. Plant out after the frosts, in mid-May, 10–15 cm apart.

Care and a second flush

• Position: sun or light shade, with midday shade in heatwaves.
• Watering: regular — even brief drying out halts flowering, especially in baskets.
• Feeding: every 2–3 weeks with a flowering-plant fertiliser; too much nitrogen means leaves, not flowers.
• Cutting back: in midsummer, when flowering fades, trim to 5 cm and feed — it flowers again in 2–3 weeks.

Lobelia contains alkaloids and is not edible — keep it away from children and pets. For balcony and basket ideas see balcony flowers and annuals for flower beds; the full A–Z is in types of flowers.

View full-size photoBushy lobelia forms cushions, trailing lobelia cascades from baskets.

FAQ

When should I sow lobelia?

From late February to mid-March; seedlings grow slowly and flower 2–2.5 months after germination.

Why did my lobelia stop flowering in summer?

Heat, dry soil or exhaustion. Cut it back to 5 cm, water and feed, and it will flower again.

Can lobelia be overwintered?

Edging lobelia is usually grown for one season; perennial cardinal flower and L. fulgens overwinter in the garden.

Author: Maria Svitlovir

Graduated from Taras Shevchenko National University of Kyiv, Institute of Biology and Medicine (2001). BSc in Biology, MSc in Horticulture. Writes about plants, works at a garden centre selecting and repotting plants, and contributes to plant reference guides.

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