Lobelia in Zone 3a & 3b
Lobelia erinus
When to plant lobelia in zone 3b
Zones 3a and 3b 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 28–Apr 4 |
|---|---|
| Direct sow / transplant outside | Jun 6–Jun 13 |
| Estimated bloom | Aug 25–Sep 1 (~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 3's season
Zone 3b's frost-free window runs about 98 days, from May 30 to September 5. 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 3b calendar · Full companion planting guide · Full plant profile · Plan your beds in the Garden Designer →
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Growing Lobelia in USDA zone 3b: when to start seeds indoors, when to direct-sow, and when to expect a bloom.
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