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When to Plant Sweet Corn in Solano County, CA

Solano County, California Zone 9b May

May to-do list for Solano County, California

A quick May briefing for Solano County, California gardeners — what's urgent, what's next, and what can wait.

Avg. last frost February 9
Avg. first frost December 3
Soil temp (4") 76°F
Watering Critical
Pest pressure High
Daylight 14.1 hrs
  1. Pick sweet corn

    Don't tug. Use scissors or pruners for clean cuts — torn stems invite disease.

Get ahead of June
  • First harvests: sweet corn

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Sweet corn is bred for high sugar content in its kernels, which convert to starch rapidly after harvest. Modern supersweet varieties hold their sweetness longer.

Solano County, California is in USDA Zone 9b. The average last spring frost is February 9 and the first fall frost is December 3, giving you a growing season of approximately 297 days.

At an elevation of 376 feet, Solano County receives approximately 40.4 inches of rainfall annually with predominantly loam soil. Summer highs average 95°F, so Sweet Corn may need afternoon shade and extra watering during peak heat.

Solano County, CA (Zone 9b) Year-round
297 days
Last Spring Frost February 9
297 growing days
First Fall Frost December 3

Solano County Soil Profile

Soil Type

Loam

Soil pH

6.8-7.3

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (200 days to spare)
Transplant: Jan 25 🍅 Harvest: Mar 29 – May 10
Recommended (50%) ✓ Fits season (192 days to spare)
Transplant: Feb 9 🍅 Harvest: Apr 13 – May 25
Safe Start (90%) ✓ Fits season (176 days to spare)
Transplant: Mar 13 🍅 Harvest: May 15 – Jun 26

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 Solano County

How your county's soil matches Sweet Corn's growing requirements.

Soil pH

Your soil pH (6.8–7.3) is more alkaline than Sweet Corn prefers (6.0–7.0). Add sulfur or peat moss to lower pH.

Soil Texture

The loam soil in Solano County is excellent for Sweet Corn — good drainage, moisture retention, and nutrient holding capacity.

Drainage

Drainage is adequate for Sweet Corn.

Organic Matter

Organic matter is moderate (2.6%). Annual compost additions will help Sweet Corn.

How to Plant Sweet Corn

1"
Planting Depth
12"
Between Plants
36"
Between Rows

Succession Planting Sweet Corn

5
successive plantings in your 297-day season

Sow every 6.9 weeks. Last sowing by Sep 04 to harvest before frost.

Plant Water Budget

Plant needs
1.5″/week
Rainfall provides
0.6″/week
You supply
1.7″/week
Watering frequency 2-3 times/week
Season total 4,394 gal / 100 sq ft
Drought risk

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

Monthly Watering Guide for Sweet Corn

Sweet Corn needs approximately 1.5 inches of water per week (6.5" per month). Here's how your county's rainfall compares month by month.

Month Sweet Corn Needs Rainfall You Supplement Action
Jan 8.9" 0" ❄️ Dormant
Feb 6.5" 8.4" 0" ✅ Rainfall sufficient
Mar 6.5" 6.6" 0" ✅ Rainfall sufficient
Apr 6.5" 2.7" 3.8" 🚿 Regular watering
May 6.5" 1" 5.5" 🚿 Regular watering
Jun 6.5" 0.2" 6.3" 🚿 Regular watering
Jul 6.5" 0" 6.5" 🚿 Regular watering
Aug 6.5" 0" 6.5" 🚿 Regular watering
Sep 6.5" 0.4" 6.1" 🚿 Regular watering
Oct 6.5" 1.9" 4.6" 🚿 Regular watering
Nov 6.5" 3.3" 3.2" 💧 Light watering
Dec 6.5" 7.1" 0" ✅ Rainfall sufficient

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

Sweet Corn 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.

Sweet Corn needs ~1,594 GDD — county provides 6,332 GDD Excellent fit

Sweet Corn Planting Timeline — Solano County, CA

Sweet Corn Planting Calendar

Activity When Date Range
Direct Sow February 16 Feb 16 – Mar 9
Harvest April 20 Apr 20 – Jun 1

Plant 1" deep · 12" apart · Rows 36" apart

Month-by-Month Timeline

MonthActivities
January
February Direct Sow
March Direct Sow
April Harvest
May Harvest
June Harvest
July
August
September
October
November
December

Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

1.5"/week · 2-3 times/week

📅 Days to Maturity

60–90 days

🧪 Soil pH

Needs 6–7 · Your soil: too_alkaline

🗺️ USDA Zone

Zone 9b

📆 Growing Season

297 days in Solano County

Growing Tips for Sweet Corn in Solano County

Direct sow Sweet Corn outdoors after February 09 in Solano County when soil has warmed and frost danger has passed.

Common pests for Sweet Corn in this region include corn earworm and corn borers. Use row covers early in the season and inspect plants weekly.

General growing tips

Plant in blocks of at least 4 rows for wind pollination. Direct sow after soil is warm. Isolate supersweet varieties from other corn types to prevent cross-pollination.

Companion Planting

Good Companions

Avoid Planting Near

  • Tomatoes

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Sweet Corn in Solano County, CA?

Solano County is in Zone 9b with an average last frost of February 9. Plan your Sweet Corn planting based on this frost date — see the calendar above for exact timing.

What planting zone is Solano County, CA?

Solano County, California is in USDA Hardiness Zone 9b. The average last spring frost is February 9 and first fall frost is December 3.

🌱

Your Solano County Garden Planner — Free

A 24-page printable planner built for Solano 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 Solano 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.