How to grow Lobelia (Crystal Palace)

Lobelia erinus

🌸 Flower 🌱 Grown each year

Clouds of tiny deep-blue flowers with bronze leaves — the classic edging and basket plant.

At a glance: Sow late January to mid February.

When to sow, plant and harvest

JanFebMarAprMayJunJulAugSepOctNovDec

Sow indoors

Plant

Flowers

Timed for a typical UK garden (last frost mid-April). The app uses your own town's frost dates.

Late January – mid February · 12 weeks before the last spring frost
Sow Seeds Indoors
Sow in trays or modules of seed compost on a warm windowsill or in a propagator. Surface-sow and prick out in small clumps rather than singly.
14–21 days after “Sow Seeds Indoors” · Early February – mid February
Check Germination
Seedlings should appear in 14–21 days. Keep the soil moist. If sown outdoors, thin them to 15 cm apart once they have two true leaves.
14–21 days after “Check Germination” · Mid February – late February
Pot On Seedlings
When seedlings have two true leaves, move each into its own small pot or module, holding them by a leaf, not the stem.
Mid April · 4 days after the last spring frost
Harden Off
Stand plants outside by day and bring them in at night for 7–10 days so they get used to outdoor conditions.
Late April – late May · 2 weeks after the last spring frost
Plant Out
Plant out 15 cm apart once frosts are over. Water in well.
69–99 days after “Check Germination” · Late April – late May
First Flowers
Take a photo for your journal!
Mid October – early November · around the first autumn frost
Clear or Collect Seed
When frost blackens the plants, pull them up for the compost heap. Leave a few seedheads first if you want to save seed.