When to plant Lobelia in Cool Australia
Cool zone — applies to Hobart, Canberra, Ballarat, Orange, Armidale and similar areas. Growing elsewhere? Temperate · Subtropical · Tropical · Arid.
Raise lobelia seedlings under cover from February to April or September to October, then transplant once frost has passed. The dust-fine seed needs light to germinate, so press it onto the surface no more than 1 mm deep and keep it moist; expect strike in 14 to 21 days. Plants reach flowering size in about 100 to 120 days, so an early start under glass pays off in cool gardens. Space transplants 15 cm apart with rows 15 to 20 cm apart. In Canberra, Ballarat and Orange, lobelia is a reliable edging and basket filler that flowers hardest through the milder end of summer.
Sowing calendar — cool zone
Green months are your sowing window: February to April and September to October.
Growing notes
Lobelia is fiddly at the seedling stage and easy once planted out, so the whole game in the cool zone is getting it through germination and hardening. Sow into punnets from February to April or September to October and do not bury the seed: it needs light, so a surface scatter pressed lightly in is right, watered from below to avoid washing it away.
The common failure is losing the tiny seedlings to damping-off in the cold, damp conditions that cool-climate autumn and early spring bring. Keep the mix on the drier side once seedlings emerge, give them good airflow, and prick out into small cells early rather than leaving them crowded. Transplant only after the last frost, as this half-hardy plant sulks or dies if put out too soon around Hobart or Armidale.
In the ground, lobelia wants steady moisture and part to full sun. Its worst summer habit is a mid-season slump where flowering stalls and the plant looks leggy. Shear it back by a third and water it through, and it will rebloom into the cooler autumn weeks. Regular liquid feeding keeps the display dense, particularly in hanging baskets and containers where the root run is limited.
Lobelia at a glance
| Sowing depth | 1 mm |
|---|---|
| Plant spacing | 15 cm |
| Row spacing | 15-20 cm |
| Germination | 14-21 days |
| Days to maturity | 100-120 days |
| Frost tolerance | Half Hardy |
| Method | Plant Seedlings |
Common questions
- Why is my lobelia seed not germinating?
- Lobelia seed needs light to sprout, so if you have buried it under soil it will not come up. Press it onto the surface only, keep it consistently moist, and allow up to 21 days at gentle warmth for germination.
- When can I plant out lobelia in Canberra?
- Wait until the last frost has passed, which in Canberra usually means mid-spring. Lobelia is half hardy and a late frost will knock back or kill young transplants, so harden them off gradually before planting into the garden.
- How do I stop lobelia going leggy in summer?
- Shear the whole plant back by about a third when flowering slows and it starts to sprawl. Water it well afterwards and give a liquid feed, and it will bush up and rebloom into the cooler part of the season.
- Can lobelia grow in hanging baskets in a cool climate?
- Yes, trailing lobelia is well suited to baskets and containers. Because the limited soil dries and starves faster, water regularly and feed with a liquid fertiliser through the flowering months to keep the display full.
Track lobelia in your garden — sow dates, harvest countdowns, reminders. Free.
Add to my garden