When to plant rosemary in zone 3b — planting calendar

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Showing USDA Zone 3B

Growing SeasonZone 3b

Last frost ~May 25First frost ~Sep 15Today

Start indoorsTransplant / sowHarvestFrost risk

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Start indoors Mar 16 · Transplant May 25 · First harvest Aug 13 · Wrap by Sep 8

Last spring frostMay 25

Start seeds indoorsMar 16

Transplant outMay 25

First harvestAug 13

Last harvestSep 8

First fall frostSep 15

Why these dates work in zone 3b

Zone 3b's last spring frost averages May 25 and first fall frost Sep 15 — about 113 frost-free days. Rosemary is frost-sensitive, so the around last frost timing builds in a safety margin against a late cold snap — setting plants out too early risks losing them to frost. Starting seeds indoors 10 weeks ahead gives strong transplants ready the moment the soil warms.

Common questions

How long does rosemary take to grow in zone 3b?

Rosemary matures in about 80–100 days from transplanting. In zone 3b that means setting plants out around May 25 and first picking around Aug 13.

Will rosemary survive frost in zone 3b?

No — rosemary is frost-sensitive. In zone 3b, wait until after the last frost (around May 25) to plant, and harvest before the first fall frost (around Sep 15).

For soil, spacing, pests and companion planting, see the full rosemary growing guide →