When to Plant Acorn Squash in Pima County, AZ
May in Pima County, Arizona — your action list
May rewards gardeners who work with the weather, not against it. Here's how to stay in step this month in Pima County, Arizona.
Acorn squash is a small winter squash with dark green, ribbed skin and mildly sweet orange flesh. It is perfect for stuffing and roasting as individual servings.
Pima County, Arizona is in USDA Zone 9b. The average last spring frost is April 1 and the first fall frost is November 9, giving you a growing season of approximately 222 days.
At an elevation of 4,327 feet, Pima County receives approximately 14.4 inches of rainfall annually with predominantly sandy loam soil. Summer highs average 103°F, so Acorn Squash may need afternoon shade and extra watering during peak heat. Sandy soil warms quickly in spring — great for early planting — but Acorn Squash will need more frequent watering and organic matter to retain nutrients. With low rainfall, drip irrigation is essential for growing Acorn Squash successfully. Mulch heavily to conserve soil moisture.
Pima County Soil Profile
Soil Type
Sandy Loam
Soil pH
6.8-8.3
Drainage
Well Drained
Plant Planting Risk Windows
Percentages indicate frost risk at transplant. The 70% safe window means there is a 30% chance of frost after transplant — suitable for cold-hardy crops or gardeners with frost protection. The 90% safe window is best for tender plants.
Soil Compatibility in Pima County
How your county's soil matches Acorn Squash's growing requirements.
Soil pH
Your soil pH (6.8–8.3) is more alkaline than Acorn Squash prefers (5.5–7.0). Add sulfur or peat moss to lower pH.
Soil Texture
Sandy soil in Pima County warms quickly in spring but drains fast. Acorn Squash will need more frequent watering and regular compost additions to retain nutrients.
Drainage
Drainage is adequate for Acorn Squash.
Organic Matter
Organic matter is low (0.9%). Add 2-3 inches of compost before planting Acorn Squash.
How to Plant Acorn Squash
Succession Planting Acorn Squash
Sow every 9.1 weeks. Last sowing by Aug 01 to harvest before frost.
Plant Water Budget
Water stress score is 10/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Acorn Squash
Acorn Squash needs approximately 1.1 inches of water per week (4.8" per month). Here's how your county's rainfall compares month by month.
| Month | Acorn Squash Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 0.9" | 0" | ❄️ Dormant |
| Feb | — | 0.8" | 0" | ❄️ Dormant |
| Mar | — | 0.7" | 0" | ❄️ Dormant |
| Apr | 4.8" | 0.5" | 4.3" | 🚿 Regular watering |
| May | 4.8" | 0.4" | 4.4" | 🚿 Regular watering |
| Jun | 4.8" | 0.5" | 4.3" | 🚿 Regular watering |
| Jul | 4.8" | 2.7" | 2.1" | 💧 Light watering |
| Aug | 4.8" | 3.2" | 1.6" | 💧 Light watering |
| Sep | 4.8" | 1.9" | 2.9" | 🚿 Regular watering |
| Oct | 4.8" | 1.4" | 3.4" | 🚿 Regular watering |
| Nov | 4.8" | 0.7" | 4.1" | 🚿 Regular watering |
| Dec | — | 0.9" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Nov in Pima County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Acorn Squash Heat Requirements (GDD)
What are Growing Degree Days (GDD)?
Growing Degree Days measure the total warmth your plants receive during the growing season. Think of it as a "heat bank" — every day above 50°F deposits warmth that helps your plants grow.
Each plant needs a certain amount of accumulated heat to mature. If your county provides more GDD than the plant needs, it's a great fit. If it's close, you may want to choose faster-maturing varieties or start seeds indoors to get a head start.
Acorn Squash Planting Timeline — Pima County, AZ
Acorn Squash Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 4 | Mar 4 – Mar 18 |
| Transplant Outdoors | April 8 | Apr 8 – Apr 22 |
| Direct Sow | April 1 | Apr 1 – Apr 22 |
| Harvest | July 1 | Jul 1 – Aug 5 |
Plant 1" deep · 30" apart · Rows 42" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | Transplant Outdoors Direct Sow |
| May | — |
| June | — |
| July | Harvest |
| August | Harvest |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1.1"/week · 2-3 times/week
📅 Days to Maturity
80–100 days
🧪 Soil pH
Needs 5.5–7 · Your soil: too_alkaline
🗺️ USDA Zone
Zone 9b
📆 Growing Season
222 days in Pima County
Growing Tips for Acorn Squash in Pima County
Direct sow Acorn Squash outdoors after April 01 in Pima County when soil has warmed and frost danger has passed.
Sandy soil in Pima County dries quickly — mulch Acorn Squash with 2-3 inches of straw and water deeply 2-3 times per week rather than lightly every day.
With summer highs reaching 103°F in Pima County, provide afternoon shade for Acorn Squash and water deeply in the morning.
Common pests for Acorn Squash in this region include squash vine borer and cucumber beetles. Use row covers early in the season and inspect plants weekly.
Pima County receives only 14" of rain annually. Acorn Squash needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.
General growing tips
Direct sow after last frost. Harvest when the ground spot turns orange and the skin is hard. Acorn squash has a shorter storage life than butternut, lasting about 2 months.
Companion Planting
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Acorn Squash in Other Locations
Frequently Asked Questions
When should I plant Acorn Squash in Pima County, AZ?
Pima County is in Zone 9b with an average last frost of April 1. Plan your Acorn Squash planting based on this frost date — see the calendar above for exact timing.
What planting zone is Pima County, AZ?
Pima County, Arizona is in USDA Hardiness Zone 9b. The average last spring frost is April 1 and first fall frost is November 9.
Your Pima County Garden Planner — Free
A 24-page printable planner built for Pima County (Zone 9b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.