When to Plant Acorn Squash in San Mateo County, CA
Top priorities for San Mateo County, California gardeners in May
Your garden in San Mateo County, California is working on a schedule, even when you're not. Here's where you should be this May.
-
Start harvesting acorn squash
Morning harvests are best — cooler temperatures mean crisper produce and longer fridge life.
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.
San Mateo County, California is in USDA Zone 10a. The average last spring frost is January 18 and the first fall frost is December 12, giving you a growing season of approximately 328 days.
At an elevation of 277 feet, San Mateo County receives approximately 16.9 inches of rainfall annually with predominantly loam soil. Summer highs average 81°F, so choose short-season varieties of Acorn Squash to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing Acorn Squash successfully. Mulch heavily to conserve soil moisture.
San Mateo County Soil Profile
Soil Type
Loam
Soil pH
6.8-7.2
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 San Mateo County
How your county's soil matches Acorn Squash's growing requirements.
Soil pH
Your soil pH (6.8–7.2) overlaps with Acorn Squash's range (5.5–7.0), though not a perfect match.
Soil Texture
The loam soil in San Mateo County is excellent for Acorn Squash — good drainage, moisture retention, and nutrient holding capacity.
Drainage
Drainage is adequate for Acorn Squash.
Organic Matter
Organic matter is moderate (2.6%). Annual compost additions will help Acorn Squash.
How to Plant Acorn Squash
Succession Planting Acorn Squash
Sow every 9.1 weeks. Last sowing by Sep 03 to harvest before frost.
Plant Water Budget
Water stress score is 8/10 — 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 | 4.8" | 3.9" | 0.9" | 💧 Light watering |
| Feb | 4.8" | 3.4" | 1.4" | 💧 Light watering |
| Mar | 4.8" | 2.7" | 2.1" | 💧 Light watering |
| Apr | 4.8" | 1.2" | 3.6" | 🚿 Regular watering |
| May | 4.8" | 0.4" | 4.4" | 🚿 Regular watering |
| Jun | 4.8" | 0.1" | 4.7" | 🚿 Regular watering |
| Jul | 4.8" | 0" | 4.8" | 🚿 Regular watering |
| Aug | 4.8" | 0" | 4.8" | 🚿 Regular watering |
| Sep | 4.8" | 0.2" | 4.6" | 🚿 Regular watering |
| Oct | 4.8" | 0.7" | 4.1" | 🚿 Regular watering |
| Nov | 4.8" | 1.4" | 3.4" | 🚿 Regular watering |
| Dec | 4.8" | 2.9" | 1.9" | 💧 Light watering |
Water needs are for active growing months only (Jan–Dec in San Mateo 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 — San Mateo County, CA
Acorn Squash Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | December 21 | Dec 21 – Jan 4 |
| Transplant Outdoors | January 25 | Jan 25 – Feb 8 |
| Direct Sow | January 18 | Jan 18 – Feb 8 |
| Harvest | April 19 | Apr 19 – May 24 |
Plant 1" deep · 30" apart · Rows 42" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | Start Indoors Transplant Outdoors Direct Sow |
| February | Transplant Outdoors Direct Sow |
| March | — |
| April | Harvest |
| May | Harvest |
| June | — |
| July | — |
| August | — |
| September | — |
| October | — |
| November | — |
| December | Start Indoors |
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: acceptable
🗺️ USDA Zone
Zone 10a
📆 Growing Season
328 days in San Mateo County
Growing Tips for Acorn Squash in San Mateo County
Direct sow Acorn Squash outdoors after January 18 in San Mateo County when soil has warmed and frost danger has passed.
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.
San Mateo County receives only 17" 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
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Acorn Squash in Other Locations
Frequently Asked Questions
When should I plant Acorn Squash in San Mateo County, CA?
San Mateo County is in Zone 10a with an average last frost of January 18. Plan your Acorn Squash planting based on this frost date — see the calendar above for exact timing.
What planting zone is San Mateo County, CA?
San Mateo County, California is in USDA Hardiness Zone 10a. The average last spring frost is January 18 and first fall frost is December 12.
Your San Mateo County Garden Planner — Free
A 24-page printable planner built for San Mateo County (Zone 10a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.