When to plant Corn in Ripon, CA
In Zone 9b (Ripon), direct-sow Corn between February 11 and March 4 for spring, after the February 4 last-frost mark.
When to Plant Corn in Ripon, CA
Your June gardening checklist
Your garden in San Joaquin County, California is working on a schedule, even when you're not. Here's where you should be this June.
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Basket week: corn
The more you pick, the more the plant produces. Letting fruit overripen tells the plant it's time to stop.
Corn is a warm-season grass grown for its sweet ears, which are best eaten soon after harvest. It is wind-pollinated and must be planted in blocks for good kernel fill.
Ripon, California is in USDA Zone 9b. The average last spring frost is February 4 and the first fall frost is December 6, giving you a growing season of approximately 305 days.
At an elevation of 220 feet, San Joaquin County receives approximately 15 inches of rainfall annually with predominantly loam soil. Summer highs average 93°F, providing good warmth for Corn during the growing season. With low rainfall, drip irrigation is essential for growing Corn successfully. Mulch heavily to conserve soil moisture.
Ripon Soil Profile
Soil Type
Loam
Soil pH
6.4-7.8
Drainage
Well Drained
Corn 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 Ripon
How your county's soil matches Corn's growing requirements.
Soil pH
Your soil pH (6.4–7.8) is more alkaline than Corn prefers (6.0–7.0). Add sulfur or peat moss to lower pH.
Soil Texture
The loam soil in San Joaquin County is excellent for Corn — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (2.5%). Annual compost additions will help Corn.
How to Plant Corn
Succession Planting Corn
Sow every 6.9 weeks. Last sowing by Aug 28 to harvest before frost.
Corn Water Budget
Water stress score is 8/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Corn
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 | Corn Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 2.9" | 0" | ❄️ Dormant |
| Feb | 6.5" | 3.1" | 3.4" | 🚿 Regular watering |
| Mar | 6.5" | 2.6" | 3.9" | 🚿 Regular watering |
| Apr | 6.5" | 1.2" | 5.3" | 🚿 Regular watering |
| May | 6.5" | 0.4" | 6.1" | 🚿 Regular watering |
| Jun | 6.5" | 0.1" | 6.4" | 🚿 Regular watering |
| Jul | 6.5" | 0" | 6.5" | 🚿 Regular watering |
| Aug | 6.5" | 0" | 6.5" | 🚿 Regular watering |
| Sep | 6.5" | 0.2" | 6.3" | 🚿 Regular watering |
| Oct | 6.5" | 0.7" | 5.8" | 🚿 Regular watering |
| Nov | 6.5" | 1.3" | 5.2" | 🚿 Regular watering |
| Dec | 6.5" | 2.6" | 3.9" | 🚿 Regular watering |
Water needs are for active growing months only (Feb–Dec in San Joaquin County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
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.
Corn Planting Timeline — Ripon, CA
Corn Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Direct Sow | February 11 | Feb 11 – Mar 4 |
| Harvest | April 15 | Apr 15 – Jun 10 |
Plant 1" deep · 12" apart · Rows 36" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| 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
60–100 days
🧪 Soil pH
Needs 6–7 · Your soil: too_alkaline
🗺️ USDA Zone
Zone 9b
📆 Growing Season
305 days in San Joaquin County
Growing Tips for Corn in Ripon
Direct sow Corn outdoors after February 04 in San Joaquin County when soil has warmed and frost danger has passed.
Common pests for Corn in this region include corn earworm and corn borers. Use row covers early in the season and inspect plants weekly.
San Joaquin County receives only 15" of rain annually. Corn needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.
General growing tips
Plant in blocks of at least 4 rows rather than single rows for proper pollination. Direct sow after soil reaches 60F. Side-dress with nitrogen when plants are knee-high.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Corn in Other Locations
When should I plant Corn in Ripon, CA?
In Ripon, CA, plant Corn after the last frost (around February 4) and before the first frost (around December 6). Best results when soil holds above 50°F.
What growing zone is Ripon, CA for Corn?
Ripon sits in USDA Zone 9b. Corn grows reliably in zones 3a through 11b, so it's a good fit here.
Can Corn grow in Ripon's climate?
Yes — Corn grows well in Ripon's temperate climate. Ripon averages a 306-day frost-free season, with last frost around February 4 and first frost around December 6.
Your San Joaquin County Garden Planner — Free
A 22-page printable planner built for San Joaquin 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.