Arizona planting calendar

When to plant broccoli in Arizona — sow, transplant & harvest dates

Arizona is mostly USDA zone 9a (range 4b-10b). Dates below are derived from broccoli's frost tolerance and Arizona's frost window — not generic national averages.

Broccoli planting timetable for Arizona

Stage	When in Arizona	Anchor
Direct-sow / set out (main)	October — February	Grown through the cool season, not summer
Shoulder sowing	September and again late February	Avoid germinating into summer heat
First harvest	~80 days after sowing (late autumn through spring)	80-day crop

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 Arizona's climate shifts the broccoli dates

Arizona flips the calendar: its winter is the productive broccoli season while northern states are frozen, and its summer is the off-season. Arizona ranges from snowy mountain forest to frost-free low desert. In the desert, summer heat is the binding constraint and winter is the prime growing season.

Start seeds indoors 6–8 weeks before last frost; transplant outdoors 2–4 weeks before last spring frost when soil reaches at least 7 °C (45 °F). Mature plants withstand temperatures as low as −6 °C (21 °F). Heads button (form premature small curds) when exposed to temperatures below 10 °C (50 °F) for extended periods as young seedlings, so harden off carefully. In zones 8–10, a second crop is practical as a fall planting, set out in late summer for harvest before hard freezes.

Frost-risk note

Light frost in the high country around Flagstaff (zone 4b-6a) only nips the outer leaves — heat, not cold, ends the crop.

Regional variation within Arizona

the low desert around Yuma and Phoenix (zone 10b) can sow earliest in autumn and latest into late winter; the high country around Flagstaff (zone 4b-6a) has a slightly shorter, frost-bracketed window.

Phoenix — USDA zone 10a
Tucson — USDA zone 9b
Flagstaff — USDA zone 6a
Yuma — USDA zone 10b
Mesa — USDA zone 10a

What else to plant in Arizona around then

The same cool window suits other greens, brassicas, peas, carrots, and radishes — fill beds October through February.

Quick-grow guide

Sun: Full sun — 6+ hours direct.
Soil temperature for germination: 7–29 °C (45–85 °F).
Spacing: 18–24 inches (45–60 cm) between plants.
Days to harvest: ~80 days from planting out.

Frequently asked questions

When is the best time to plant broccoli in Arizona?

In Arizona (mostly USDA zone 9a), grow broccoli as a cool-season crop: direct-sow from October through February, harvest ~80 days later, and skip summer entirely — heat above 24 °C bolts it. Broccoli 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 Arizona?

Most of Arizona sits in USDA hardiness zone 9a, with the state spanning roughly 4b-10b from the high country around Flagstaff (zone 4b-6a) to the low desert around Yuma and Phoenix (zone 10b). The last spring frost averages mid-February (low desert) and the first fall frost early December (low desert).

Can you grow broccoli in Arizona?

Yes. Arizona's dominant zone 9a supports broccoli — the key is timing. Broccoli 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 Arizona?

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

The same cool window suits other greens, brassicas, peas, carrots, and radishes — fill beds October through February.

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.