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When to Plant Tomatoes in Glenn County, CA

Tomatoes are the most popular home garden crop, available in thousands of varieties from tiny cherries to massive beefsteaks. They are warm-season plants needing full sun.

Glenn County, California is in USDA Zone 9a. The average last spring frost is March 6 and the first fall frost is November 28, giving you a growing season of approximately 267 days.

At an elevation of 270 feet, Glenn County receives approximately 27.1 inches of rainfall annually with predominantly loam soil. Summer highs average 88ยฐF, providing good warmth for Tomatoes during the growing season.

Glenn County, CA (Zone 9a) Long season
267 days
Last Spring Frost March 6
267 growing days
First Fall Frost November 28

Glenn County Soil Profile

Soil Type

Loam

Soil pH

6.5-7.9

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (130 days to spare)
Start indoors: Jan 12 Transplant: Mar 2 🍅 Harvest: May 4 – Jul 13
Recommended (50%) ✓ Fits season (127 days to spare)
Start indoors: Jan 23 Transplant: Mar 13 🍅 Harvest: May 15 – Jul 24
Safe Start (90%) ✓ Fits season (105 days to spare)
Start indoors: Mar 7 Transplant: Apr 25 🍅 Harvest: Jun 27 – Sep 5

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.

Plant Water Budget

Plant needs
1.0″/week
Rainfall provides
0.4″/week
You supply
0.7″/week
Watering frequency 1-2 times/week
Season total 1,636 gal / 100 sq ft
Drought risk

Water stress score is 8/10 โ€” consider drought-tolerant varieties and mulching

Tomatoes needs ~1,160 GDD — county provides 4,272 GDD Excellent fit

Tomatoes Planting Timeline โ€” Glenn County, CA

Tomatoes Planting Calendar

Activity When Date Range
Start Indoors January 23 Jan 23 โ€“ Feb 6
Transplant Outdoors March 13 Mar 13 โ€“ Mar 27
Direct Sow March 6 Mar 6 โ€“ Mar 27
Harvest May 15 May 15 โ€“ Jul 24

Plant 0.5" deep ยท 24" apart ยท Rows 36" apart

Month-by-Month Timeline

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

Growing Conditions

Sun

Full Sun (6-8+ hours)

Water

Moderate โ€” regular watering

Days to Maturity

60โ€“85 days

Soil pH

6 โ€“ 7

USDA Zone

Zone 9a

Growing Season

267 days

Growing Tips for Glenn County

Start seeds indoors 6-8 weeks before last frost. Bury transplants deep to encourage rooting along the stem. Provide consistent moisture to prevent blossom end rot and cracking.

Companion Planting

Good Companions

Avoid Planting Near

  • Cabbage
  • Fennel
  • Potatoes

Level Up Your Garden

๐ŸŒพ Save Your Own Tomatoes Seeds
Life Cycle Annual
Pollination Self-Pollinating
How to Collect Scoop seeds from ripe fruit; ferment 2-3 days to remove gel coating.
Storage Store airtight; viable 4-6 years at 35ยฐF, under 45% humidity.

Isolate 25 ft between varieties for purity. Use open-pollinated varieties for true-to-type seeds.

Frequently Asked Questions

When should I plant Tomatoes in Glenn County, CA?

Glenn County is in Zone 9a with an average last frost of March 6. Plan your Tomatoes planting based on this frost date โ€” see the calendar above for exact timing.

What planting zone is Glenn County, CA?

Glenn County, California is in USDA Hardiness Zone 9a. The average last spring frost is March 6 and first fall frost is November 28.

๐ŸŒฑ

Plan Your Garden with Confidence

Get our free Garden Planner โ€” designed to help Glenn County gardeners in Zone 9a organize planting dates, track what's growing, and never miss a planting window.

Get Your Free Garden Planner →

Free download. Plan your entire garden season in minutes.

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