Lobelia in Zone 5a & 5b
Lobelia erinus
When to plant lobelia in zone 5b
Zones 5a and 5b 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 8–Mar 15 |
|---|---|
| Direct sow / transplant outside | May 17–May 24 |
| Estimated bloom | Aug 5–Aug 12 (~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 5's season
Zone 5b's frost-free window runs about 148 days, from May 10 to October 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 5b calendar · Full companion planting guide · Full plant profile · Plan your beds in the Garden Designer →
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Growing Lobelia in USDA zone 5b: when to start seeds indoors, when to direct-sow, and when to expect a bloom.
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