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When to Plant Squash (Summer) in Mariposa County, CA

Mariposa County, California Zone 9b May

May to-do list for Mariposa County, California

May rewards gardeners who work with the weather, not against it. Here's how to stay in step this month in Mariposa County, California.

Avg. last frost April 18
Avg. first frost November 9
Soil temp (4") 68°F
Watering Critical
Pest pressure Moderate
Daylight 14 hrs
  1. Start squash (summer) under lights

    You're about 26 weeks out from your last frost — the perfect window to get these germinating indoors.

June will be here before you know it — start on
  • First harvests: squash (summer)

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Summer squash includes zucchini, yellow crookneck, and pattypan varieties that are harvested young and tender. They are prolific producers in warm weather.

Mariposa County, California is in USDA Zone 9b. The average last spring frost is April 18 and the first fall frost is November 9, giving you a growing season of approximately 205 days.

At an elevation of 192 feet, Mariposa County receives approximately 19.2 inches of rainfall annually with predominantly loam soil. Summer highs average 91°F, providing good warmth for Squash (Summer) during the growing season. With low rainfall, drip irrigation is essential for growing Squash (Summer) successfully. Mulch heavily to conserve soil moisture.

Mariposa County, CA (Zone 9b) Long season
205 days
Last Spring Frost April 18
205 growing days
First Fall Frost November 9
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Mariposa County Soil Profile

Soil Type

Loam

Soil pH

6.5-7.5

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (101 days to spare)
Start indoors: Feb 24 Transplant: Mar 31 🍅 Harvest: May 19 – Jul 21
Recommended (50%) ✓ Fits season (86 days to spare)
Start indoors: Mar 21 Transplant: Apr 25 🍅 Harvest: Jun 13 – Aug 15
Safe Start (90%) ✓ Fits season (80 days to spare)
Start indoors: Apr 20 Transplant: May 25 🍅 Harvest: Jul 13 – Sep 14

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 Mariposa County

How your county's soil matches Squash (Summer)'s growing requirements.

Soil pH

Your soil pH (6.5–7.5) is within Squash (Summer)'s preferred range (6.0–7.5).

Soil Texture

The loam soil in Mariposa County is excellent for Squash (Summer) — good drainage, moisture retention, and nutrient holding capacity.

Organic Matter

Organic matter is moderate (2.8%). Annual compost additions will help Squash (Summer).

How to Plant Squash (Summer)

1"
Planting Depth
30"
Between Plants
42"
Between Rows

Succession Planting Squash (Summer)

5
successive plantings in your 205-day season

Sow every 5.1 weeks. Last sowing by Sep 05 to harvest before frost.

Plant Water Budget

Plant needs
1.0″/week
Rainfall provides
0.4″/week
You supply
0.7″/week
Watering frequency 2-3 times/week
Season total 1,328 gal / 100 sq ft
Drought risk

Water stress score is 8/10 — consider drought-tolerant varieties and mulching

Monthly Watering Guide for Squash (Summer)

Squash (Summer) needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.

Month Squash (Summer) Needs Rainfall You Supplement Action
Jan 3.7" 0" ❄️ Dormant
Feb 4.3" 0" ❄️ Dormant
Mar 3.2" 0" ❄️ Dormant
Apr 4.3" 1.6" 2.7" 🚿 Regular watering
May 4.3" 0.5" 3.8" 🚿 Regular watering
Jun 4.3" 0.1" 4.2" 🚿 Regular watering
Jul 4.3" 0" 4.3" 🚿 Regular watering
Aug 4.3" 0" 4.3" 🚿 Regular watering
Sep 4.3" 0.2" 4.1" 🚿 Regular watering
Oct 4.3" 0.9" 3.4" 🚿 Regular watering
Nov 4.3" 1.9" 2.4" 🚿 Regular watering
Dec 2.8" 0" ❄️ Dormant

Water needs are for active growing months only (Apr–Nov in Mariposa County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.

Squash (Summer) 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.

Squash (Summer) needs ~1,004 GDD — county provides 3,741 GDD Excellent fit

Squash (Summer) Planting Timeline — Mariposa County, CA

Squash (Summer) Planting Calendar

Activity When Date Range
Start Indoors March 21 Mar 21 – Apr 4
Transplant Outdoors April 25 Apr 25 – May 9
Direct Sow April 18 Apr 18 – May 9
Harvest June 13 Jun 13 – Aug 15

Plant 1" deep · 30" apart · Rows 42" apart

Month-by-Month Timeline

MonthActivities
January
February
March Start Indoors
April Start Indoors Transplant Outdoors Direct Sow
May Transplant Outdoors Direct Sow
June Harvest
July Harvest
August Harvest
September
October
November
December
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Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

1"/week · 2-3 times/week

📅 Days to Maturity

45–65 days

🧪 Soil pH

Needs 6–7.5 · Your soil: ideal

🗺️ USDA Zone

Zone 9b

📆 Growing Season

205 days in Mariposa County

Growing Tips for Squash (Summer) in Mariposa County

Direct sow Squash (Summer) outdoors after April 18 in Mariposa County when soil has warmed and frost danger has passed.

Your generous 205.0-day season in Mariposa County allows multiple plantings of Squash (Summer). Sow every 22.0 days for continuous harvest.

Common pests for Squash (Summer) in this region include squash vine borer and cucumber beetles. Use row covers early in the season and inspect plants weekly.

Mariposa County receives only 19" of rain annually. Squash (Summer) needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.

General growing tips

Direct sow after last frost on mounds. Harvest frequently when fruits are 6-8 inches for best texture. Check plants daily as they grow rapidly in summer heat.

Companion Planting

Good Companions

Avoid Planting Near

  • Potatoes

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Squash (Summer) in Mariposa County, CA?

Mariposa County is in Zone 9b with an average last frost of April 18. Plan your Squash (Summer) planting based on this frost date — see the calendar above for exact timing.

What planting zone is Mariposa County, CA?

Mariposa County, California is in USDA Hardiness Zone 9b. The average last spring frost is April 18 and first fall frost is November 9.

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Your Mariposa County Garden Planner — Free

A 24-page printable planner built for Mariposa 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.

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Data sources: USDA Plant Hardiness Zone Map (2023), NOAA 30-Year Climate Normals. Frost dates are based on 50% probability averages for Mariposa County, CA. Local conditions may vary. Last updated: May 2026.

Sources & credits

Every number on this page traces back to a primary horticulture or government data source. Click through to verify.