When to Plant Basil in Arizona
Published: April 21, 2026
Arizona gardeners in Zone 9b enjoy an extended 50-week growing season for basil. Warm-climate gardeners can grow two basil crops — a spring planting and a fall planting — with summer heat as the main challenge to work around. This guide gives exact dates for Arizona based on your local frost calendar.
Basil Planting Dates for Arizona
| Start seeds indoors | December 4–11 |
| Last frost (average) | January 15 |
| Transplant outdoors | January 29–February 8 |
| Direct sow outdoors | January 29–February 8 |
| Expect first harvest | February 28 – March 30 |
| First fall frost (average) | December 31 |
Dates above assume Zone 9b, the most common zone in Arizona. Gardeners in cooler San Tan Valley (Zone 7b) plant 1–2 weeks later; warmer Tucson (Zone 9a) can plant 1–2 weeks earlier.
Growing Basil in Arizona's Climate
Arizona's warm Zone 9b climate gives basil more than enough heat — in fact, peak summer heat (95°F+) can shut down fruit set entirely. The solution most Arizona gardeners use is a two-season approach: a spring crop planted early, a harvest break during peak summer, and a fall crop planted July through August for October and November harvest.
Variety selection matters more in warm climates than most gardeners realize. Choose heat-tolerant varieties bred for Arizona-like conditions — local extension offices and nurseries stock these specifically. Afternoon shade cloth during July and August can be the difference between a working fall crop and total flower drop.
Common basil pests to watch for in Arizona include Aphids and Spider Mite. The first line of defense is companion planting: Tomato and Pepper planted nearby discourage several of these pests by confusing host-plant identification or repelling adults before they can lay eggs. Weekly garden walks in the early morning catch problems when they're still manageable.
Basil Garden Calendar for Arizona
| Month | Task | Notes |
|---|---|---|
| January | Transplant outdoors | Soil temp must be 60°F+; nighttime lows above 50°F |
| February | First harvest window opens | Basil begins producing 30–60 days after transplant |
| March | — | Off-season |
| April | — | Off-season |
| May ← | — | Off-season |
| June | Peak growth; water 1 inch/week | Monitor for pests daily; stake or support as needed |
| July | Continue care | Consistent watering; remove yellow leaves |
| August | — | Off-season |
| September | — | Off-season |
| October | — | Off-season |
| November | — | Off-season |
| December | Start seeds indoors | Use grow lights; warm soil to 70–75°F for best germination |
Basil Growing Tips for Arizona Gardeners
- •Never expose basil to temperatures below 50°F — even briefly — it turns black and dies.
- •Pinch flower buds immediately as they appear to keep leaves large and productive.
- •Arizona's summer heat shuts down basil flowering at 95°F+. Choose heat-tolerant varieties and use shade cloth from mid-June through August to preserve fruit set.
- •Harvest by cutting whole stems from the top, leaving lower sets of leaves to branch out.
Companion Planting for Basil in Arizona
In Arizona's warm climate, planting basil with Tomato and Pepper helps deter pests and improve soil. Avoid planting near Sage and Fennel, which inhibit basil growth through root chemistry or shared pest pressure. See the full basil companion planting guide for the complete list.
Basil Planting Dates by City in Arizona
Top cities in Arizona — select for city-level frost dates and planting calendars.
Frequently Asked Questions
When should I plant basil in Arizona?
In Arizona (Zone 9b), start basil seeds indoors around December 4–11 and transplant outdoors around January 29–February 8 — 2 weeks after the state's average last frost of January 15.
What is the last frost date in Arizona?
Arizona's average last frost date is January 15 in the state's most common Zone 9b. Frost dates vary by city — higher elevations and northern counties run 1 to 3 weeks later than the state average. See the city list below for city-level frost dates.
Can I grow basil year-round in Arizona?
Not year-round — Arizona's cold season stops basil production. The basil season runs January 15 to December 31, roughly 50 weeks.
What basil varieties grow best in Arizona?
For Arizona's Zone 9b, Thai Basil, Holy Basil, and Lime Basil tolerate heat better than classic Genovese.
When do I start basil seeds indoors in Arizona?
Start basil seeds indoors in Arizona around December 4–11, which is 6 weeks before the state's average last frost of January 15. Use grow lights and keep soil temperatures at 70–75°F for fastest germination.