Phlox (Annual) in Zone 3a & 3b
Phlox drummondii
When to plant phlox (annual) in zone 3b
Zones 3a and 3b share the same average frost dates in our data, so this page covers both.
Method: Either: Start indoors for an earlier harvest, or direct-sow outside for less fuss. Phlox (Annual) tolerates either.
| Start indoors | Apr 25–May 2 |
|---|---|
| Direct sow / transplant outside | May 23–May 30 |
| Estimated bloom | Aug 1–Aug 8 (~70 days after planting) |
Spacing: 2 per square foot (square-foot-gardening spacing). Mature height: 0.5-1.5 ft.
Annual phlox is a compact, fast, and easy bedding flower in unusually bright, saturated colors, worth telling apart from the taller, perennial garden phlox that shares the common name but grows and behaves quite differently.
How phlox (annual) fits zone 3's season
Zone 3b's frost-free window runs about 98 days, from May 30 to September 5. Phlox (Annual) needs about 70 days from sowing to first harvest.
Good companions
No standout companions recorded yet for Phlox (Annual).
Where to buy phlox seeds
See why we recommend these suppliers →
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See it growing
Search YouTube for "growing phlox (annual)" 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 Phlox (Annual) in USDA zone 3b: when to start seeds indoors, when to direct-sow, and when to expect a bloom.
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