California planting calendar

When to plant thyme in California — sow, transplant & harvest dates

California is mostly USDA zone 9b (range 5a-11a). Dates below are derived from thyme's frost tolerance and California's frost window — not generic national averages.

Thyme planting timetable for California

Stage	When in California	Anchor
Start seeds indoors (spring crop)	late December (December 21)	8 weeks before the last frost (mid-February (coast) to late April (interior))
Transplant outside (spring crop)	mid-February (February 15)	0 days after the last frost (mid-February (coast) to late April (interior))
Spring-crop harvest	mid-May onward, before peak summer heat	85-day crop — finishes before mid-summer
Plant the fall crop	early August (August 8) — once the worst heat breaks	~99 days before the first fall frost (mid-November (coast) to mid-October (interior))
Fall-crop harvest	early November into early winter	85-day crop — often the more productive of the two

Dates are state-wide averages for the dominant zone. Local microclimates — elevation, urban heat, coastal moderation — can shift the window by 1-2 weeks. Use the frost-date calculator for a date tuned to your town.

Why California's climate shifts the thyme dates

California's long hot summer shuts down fruit set, so locals run two short crops — a spring planting and a fall planting — around a deliberate mid-summer pause, instead of one long northern-style season. California packs more climate diversity than almost any state — alpine mountains, Mediterranean coast, Central Valley farmland, and desert. Coastal and valley areas grow year-round.

Start seeds indoors 8–10 weeks before the last spring frost; germination takes 14–21 days at 18–21 °C (65–70 °F). Harden off transplants and set out around the date of last frost — thyme is perennial in USDA zones 5–9 (RHS H5) but resents waterlogged soil far more than cold. In the first growing season allow only light harvesting so the plant can establish; full harvests from the second year onward, cutting stems back to 4–5 cm above woody growth.

Frost-risk note

A light frost in the high Sierra Nevada (zone 5a-6a) can clip an early spring planting; the bigger risk is mid-summer heat sterilising flowers.

Regional variation within California

the southern coast and Imperial Valley (zone 11a) can start the spring crop weeks earlier and may garden almost year-round; the high Sierra Nevada (zone 5a-6a) runs a shorter, more northern-style single season.

Los Angeles — USDA zone 10b
San Francisco — USDA zone 10b
Sacramento — USDA zone 9b
San Diego — USDA zone 10b
Fresno — USDA zone 9b

What else to plant in California around then

Pair the spring slot with other heat-lovers (peppers, squash, beans); use the cool October–February window for greens and brassicas.

Quick-grow guide

Sun: Full sun — 6+ hours direct.
Soil temperature for germination: 18–21 °C (65–70 °F).
Spacing: 6–8 inches (15–20 cm) between plants.
Days to harvest: ~85 days from planting out.

Frequently asked questions

When is the best time to plant thyme in California?

In California (mostly USDA zone 9b), sow thyme indoors around late December, set the spring crop out mid-February, harvest before peak summer heat, then plant a second crop early August for an autumn harvest. Avoid mid-summer. Thyme are cold-hardy — they tolerate frost and actively prefer cool weather, so they go in well before the last spring frost and bolt in summer heat.

What USDA zone is California?

Most of California sits in USDA hardiness zone 9b, with the state spanning roughly 5a-11a from the high Sierra Nevada (zone 5a-6a) to the southern coast and Imperial Valley (zone 11a). The last spring frost averages mid-February (coast) to late April (interior) and the first fall frost mid-November (coast) to mid-October (interior).

Can you grow thyme in California?

Yes. California's dominant zone 9b supports thyme — the key is timing. Thyme are cold-hardy — they tolerate frost and actively prefer cool weather, so they go in well before the last spring frost and bolt in summer heat.

Does the planting date change across California?

What else can I plant in California around the same time?

Pair the spring slot with other heat-lovers (peppers, squash, beans); use the cool October–February window for greens and brassicas.

Source and methodology

State zone spans from the USDA Plant Hardiness Zone Map (2023); frost-date averages from NOAA Climate Data Online. Hot-state two-season timing cross-checked against the UF/IFAS Florida Gardening Calendar and the University of Arizona Cooperative Extension planting calendar. Curated by the Growli editorial team.