Lobelia in Zone 4a & 4b
Lobelia erinus
When to plant lobelia in zone 4b
Zones 4a and 4b share the same average frost dates in our data, so this page covers both.
Method: Start indoors: Start indoors from seed, then transplant outside. Lobelia needs a head start most zones can't give it by direct-sowing alone.
| Start indoors | Mar 13–Mar 20 |
|---|---|
| Direct sow / transplant outside | May 22–May 29 |
| Estimated bloom | Aug 10–Aug 17 (~80 days after transplanting) |
Spacing: 4 per square foot (square-foot-gardening spacing). Mature height: 4-8 in.
Lobelia is the smallest flower in this dataset and one of the earliest to start indoors, which catches people out.
How lobelia fits zone 4's season
Zone 4b's frost-free window runs about 128 days, from May 15 to September 20. Lobelia needs about 80 days from transplant to first harvest.
Good companions
No standout companions recorded yet for Lobelia.
Where to buy lobelia seeds
See why we recommend these suppliers →
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See it growing
Search YouTube for "growing lobelia" videos → (a live search, not a hand-picked video; results vary and aren't vetted by us)
← Back to the full zone 4b calendar · Full companion planting guide · Full plant profile · Plan your beds in the Garden Designer →
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Growing Lobelia in USDA zone 4b: when to start seeds indoors, when to direct-sow, and when to expect a bloom.
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