When to Plant Brussels Sprouts in Tempe, AZ
Published: April 24, 2026
Brussels Sprout Planting Dates for Tempe, AZ
| Start seeds indoors | December 11–18 |
| Last frost (average) | January 15 |
| Transplant outdoors | April 9–19 |
| Minimum soil temperature | 45°F |
| Expect first harvest | June 28 – July 18 |
| Fall crop planting | October 1–11 |
| Fall crop harvest | December 20 |
| First fall frost (average) | December 31 |
⚠ Brussels sprouts are planted in midsummer for a fall harvest. Count back 90 days from your first fall frost to find the transplant date. Start seeds indoors 4–6 weeks before that date. Flavor improves after frost.
Best Brussels Sprout Varieties for Tempe, AZ
Consult a Tempe-area nursery or your state extension office for brussels sprout varieties proven in Zone 9b.
Growing Brussels Sprouts in Tempe
Tempe sits in Zone 9b, with an average last frost of January 15 and first fall frost around December 31 — giving a 350-day frost-free growing season. Cool-season crops like brussels sprout benefit from Tempe's cooler spring and fall windows, when temperatures stay in the 55–75°F sweet spot that produces the best flavor and least bolting.
In Tempe's warm climate, brussels sprout works best as a fall, winter, and early-spring crop. Summer heat bolts most cool-season vegetables before they can produce a harvestable head or root. Plan primary plantings in October through February in Tempe, not April through June.
Tempe's caliche soil is rock-hard below the surface — raised beds filled with quality potting mix are the most practical approach for brussels sprout. Breaking through caliche for in-ground planting requires significant soil amendment, gypsum application, and deep tilling over several seasons. Water at 1.5 inches per week delivered through drip irrigation for best results in a raised-bed system.
Brussels Sprout Calendar for Tempe
| Month | Task |
|---|---|
| December | Start seeds indoors under grow lights |
| January | Last frost — harden off seedlings outdoors |
| April | Transplant outdoors into warm soil |
| June | Expect first harvest window to open |
| October | Start fall crop — transplants or direct sow |
| December | First fall frost — harvest remaining, end of outdoor season |
Brussels Sprout Tips for Tempe Gardeners
- •Count back 90 days from first fall frost to find the transplant date — this is the most important Brussels sprout timing rule.
- •Pinch the top of each plant about a month before first frost — this channels energy into sprout formation.
- •Plant cool-season brussels sprout in Tempe during October through February — spring plantings bolt before producing a usable crop in warm zones.
Common Brussels Sprout Pests in Tempe
- •Cabbage Worm — peaks June–August in Zone 9b (active March–October); green caterpillars on brassicas; apply Bt spray or use row covers.
- •Aphid — peaks June–August in Zone 9b (active March–October); monitor closely during peak season and treat early.
- •Cabbage Looper — peaks June–August in Zone 9b (active March–October); loop-walking green caterpillars; Bt spray works well.
Check plants every 2–3 days during peak season — early intervention prevents most infestations from becoming serious.
What to Plant with Brussels Sprouts in Tempe
In Tempe's warm climate, Onion and Celery are the most beneficial plants to grow alongside brussels sprout. Onion deters carrot fly, aphids, and several root-zone pests through sulfur compounds. Keep brussels sprout away from Tomato — it competes for nutrients or shares pest pressure. Warm-climate gardeners especially benefit from dense, layered companion plantings that shade soil and reduce water loss.
Frequently Asked Questions
When should I plant brussels sprout in Tempe, AZ?
In Tempe (Zone 9b), start brussels sprout seeds indoors around December 11–18 and transplant outdoors around April 9–19. The city's average last frost of January 15 is the anchor date — count 5 weeks back for seed starting and 12 weeks forward for transplanting.
What zone is Tempe, AZ for brussels sprout growing?
Tempe is USDA Zone 9b. For brussels sprout, this means a frost-free growing season of roughly 50 weeks running from January 15 to December 31. Cool-season crops like brussels sprout thrive in this zone with both spring and fall planting windows available.
When is brussels sprout harvest season in Tempe?
Expect the first brussels sprout harvest in Tempe around June 28, with harvest continuing through July 18. This is based on 80–100 days from transplant or direct sow. A fall crop planted October 1–11 adds a second harvest around December 20.
How long does it take to grow brussels sprout in Tempe, AZ?
From transplant or direct sow to first harvest, brussels sprout takes 80–100 days in Tempe's climate. Based on a typical planting date of April 9–19, expect your first harvest around June 28. Tempe's warm Zone 9b climate tends toward the faster end of this range — warmer soil and longer days accelerate maturity.
What soil does brussels sprout need in Tempe?
Tempe's caliche subsoil is effectively rock — traditional in-ground planting of brussels sprout produces poor results. Build a raised bed with 12–18 inches of quality potting mix or Mel's Mix for reliable production. Break through caliche only for deep-rooted crops, and expect to add compost each year to offset the alkalinity.