When to Plant Cauliflower in Rock Island County, IL
This month in Rock Island County, Illinois
A quick May briefing for Rock Island County, Illinois gardeners — what's urgent, what's next, and what can wait.
-
Indoor seed-starting week for cauliflower
Label every cell. You will absolutely forget which is which otherwise.
A few tasks this May that'll pay off in June
- First harvests: cauliflower
Cauliflower is a cool-season brassica that produces dense white, purple, or green heads called curds. It is more finicky than broccoli but rewards with a mild, nutty flavor.
Rock Island County, Illinois is in USDA Zone 5b. The average last spring frost is April 15 and the first fall frost is October 19, giving you a growing season of approximately 187 days.
At an elevation of 1,172 feet, Rock Island County receives approximately 35.8 inches of rainfall annually with predominantly silt loam soil. Summer highs average 83°F, so choose short-season varieties of Cauliflower to ensure they mature before fall.
Rock Island County Soil Profile
Soil Type
Silt Loam
Soil pH
6.3-6.9
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 Rock Island County
How your county's soil matches Cauliflower's growing requirements.
Soil pH
Your soil pH (6.3–6.9) is within Cauliflower's preferred range (6.0–7.0).
Soil Texture
The silt loam soil in Rock Island County is excellent for Cauliflower — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (4.7%) — Cauliflower will thrive.
How to Plant Cauliflower
Fall planting: Sow 10 weeks before your first frost date for a fall harvest.
Succession Planting Cauliflower
Sow every 6.3 weeks. Last sowing by Jul 11 to harvest before frost.
For a dedicated fall crop, sow by Aug 10.
Plant Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Cauliflower
Cauliflower needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Cauliflower Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.7" | 0" | ❄️ Dormant |
| Feb | — | 1.4" | 0" | ❄️ Dormant |
| Mar | — | 2.2" | 0" | ❄️ Dormant |
| Apr | 4.3" | 3.6" | 0.7" | 💧 Light watering |
| May | 4.3" | 4.2" | 0.1" | 💧 Light watering |
| Jun | 4.3" | 4.7" | 0" | ✅ Rainfall sufficient |
| Jul | 4.3" | 3.5" | 0.8" | 💧 Light watering |
| Aug | 4.3" | 4.2" | 0.1" | 💧 Light watering |
| Sep | 4.3" | 2.7" | 1.6" | 💧 Light watering |
| Oct | 4.3" | 2.8" | 1.5" | 💧 Light watering |
| Nov | — | 2.6" | 0" | ❄️ Dormant |
| Dec | — | 2.2" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Rock Island County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Cauliflower 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.
Cauliflower Planting Timeline — Rock Island County, IL
Cauliflower Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 11 | Mar 11 – Mar 25 |
| Transplant Outdoors | April 15 | Apr 15 – Apr 29 |
| Direct Sow | April 1 | Apr 1 – Apr 22 |
| Harvest | June 10 | Jun 10 – Aug 12 |
| Fall Sowing | August 10 | Aug 10 – Aug 24 |
Plant 1" deep · 15" apart · Rows 24" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | Transplant Outdoors Direct Sow |
| May | — |
| June | Harvest |
| July | Harvest |
| August | Fall Sowing Harvest |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1"/week · Only during dry spells
📅 Days to Maturity
55–100 days
🧪 Soil pH
Needs 6–7 · Your soil: ideal
🗺️ USDA Zone
Zone 5b
📆 Growing Season
187 days in Rock Island County
Growing Tips for Cauliflower in Rock Island County
Direct sow Cauliflower outdoors after April 15 in Rock Island County when soil has warmed and frost danger has passed.
Common pests for Cauliflower in this region include cabbage worm and flea beetles. Use row covers early in the season and inspect plants weekly.
General growing tips
Start seeds indoors 6 weeks before transplanting. Blanch white varieties by tying outer leaves over the head. Provide consistent moisture and avoid temperature extremes.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Cauliflower in Other Locations
Frequently Asked Questions
When should I plant Cauliflower in Rock Island County, IL?
Rock Island County is in Zone 5b with an average last frost of April 15. Plan your Cauliflower planting based on this frost date — see the calendar above for exact timing.
What planting zone is Rock Island County, IL?
Rock Island County, Illinois is in USDA Hardiness Zone 5b. The average last spring frost is April 15 and first fall frost is October 19.
Your Rock Island County Garden Planner — Free
A 24-page printable planner built for Rock Island County (Zone 5b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.