When to plant thyme in zone 4b — planting calendar

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Showing USDA Zone 4B

Growing SeasonZone 4b

Last frost ~May 15First frost ~Sep 25Today

Start indoorsTransplant / sowHarvestFrost risk

MARAPRMAYJUNJULAUGSEPOCT

Start indoors Mar 20 · Transplant May 8 · First harvest Jul 7 · Wrap by Sep 25

Last spring frostMay 15

Start seeds indoorsMar 20

Transplant outMay 8

First harvestJul 7

Last harvestSep 25

First fall frostSep 25

Why these dates work in zone 4b

Zone 4b's last spring frost averages May 15 and first fall frost Sep 25 — about 133 frost-free days. Thyme tolerates light frost, so you can set plants out ahead of the last-frost date and keep harvesting into the cooler fall. Starting seeds indoors 8 weeks ahead gives strong transplants ready the moment the soil warms.

Common questions

How long does thyme take to grow in zone 4b?

Thyme matures in about 60–90 days from transplanting. In zone 4b that means setting plants out around May 8 and first picking around Jul 7.

Will thyme survive frost in zone 4b?

Yes — thyme tolerates light frost. In zone 4b you can set plants out a little before the last frost (around May 15) and keep harvesting past the first fall frost (around Sep 25).

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