Plant Basil in Zone 4b
Seed-starting, transplant & harvest dates for USDA Zone 4b
Zone 4b averages 146 frost-free days, running from a last spring frost around May 5 to a first fall frost around September 28. Basil needs roughly 60 days from planting out to first harvest, so it uses about 41 percent of that window. Basil is a tender crop, which is what decides where in the window it belongs.
Because basil needs a head start, sow seed indoors around Mar 24, about 6 weeks ahead of the Zone 4b last frost. Transplants go out around May 19. Starting earlier than that in Zone 4b usually backfires: plants outgrow their cells and stall when they finally hit cold soil.
Fall planting: basil in Zone 4b
Basil has no useful fall window in Zone 4b. Basil blackens at the first light frost, so there is no fall window. Move a plant indoors under a light instead.
Basil blackens at the first light frost, so there is no fall window. Move a plant indoors under a light instead.
Fall dates are counted backward from the Zone 4b average first frost, not forward from a sowing date. See the fall planting calendar by zone for the full method.
Spring vs fall basil in Zone 4b
| Planting | Sow or start | In the ground | Harvest |
|---|---|---|---|
| Spring | Mar 24 | May 19 | Jul 18 |
| Fall | — | — | — |
Basil in nearby zones
Further reading on basil
- When to start seeds indoors by zone
Indoor start dates for basil, counted back from your last frost.
- Hardening off seedlings: a schedule
A day by day plan for moving basil seedlings outdoors.
- Best grow lights for seed starting
What light seedlings actually need, and which fixtures deliver it.
Other crops in Zone 4b
Frequently asked questions
When should I start basil in Zone 4b?
Start basil seeds indoors around Mar 24 (Zone 4b).
Can I direct sow basil in Zone 4b?
Yes, direct sow around May 19.
Can I plant basil in the fall in Zone 4b?
Basil has no useful fall window in Zone 4b. Basil blackens at the first light frost, so there is no fall window. Move a plant indoors under a light instead.
Will basil survive frost in Zone 4b?
No. Basil is a tender crop and a single light frost ends it, so every Zone 4b planting has to finish before the average first frost.