When to Plant Brussels Sprouts in Brown County, IL
Brussels sprouts are a cold-hardy brassica that produces miniature cabbage-like heads along a tall stalk. Flavor improves after a light frost.
Brown County, Illinois is in USDA Zone 5b. The average last spring frost is April 17 and the first fall frost is October 16, giving you a growing season of approximately 182 days.
At an elevation of 868 feet, Brown County receives approximately 36.2 inches of rainfall annually with predominantly silt loam soil. Summer highs average 86°F, providing good warmth for Brussels Sprouts during the growing season.
Brown County Soil Profile
Soil Type
Silt Loam
Soil pH
6.3-6.8
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 Brown County
How your county's soil matches Brussels Sprouts's growing requirements.
Soil pH
Your soil pH (6.3–6.8) is within Brussels Sprouts's preferred range (6.0–7.5).
Soil Texture
The silt loam soil in Brown County is excellent for Brussels Sprouts — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (5.2%) — Brussels Sprouts will thrive.
How to Plant Brussels Sprouts
Fall planting: Sow 10 weeks before your first frost date for a fall harvest.
Plant Water Budget
Monthly Watering Guide for Brussels Sprouts
Brussels Sprouts needs approximately 0.9 inches of water per week (3.9" per month). Here's how your county's rainfall compares month by month.
| Month | Brussels Sprouts Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.7" | 0" | ❄️ Dormant |
| Feb | — | 1.4" | 0" | ❄️ Dormant |
| Mar | — | 2.3" | 0" | ❄️ Dormant |
| Apr | 3.9" | 3.4" | 0.5" | 💧 Light watering |
| May | 3.9" | 4.2" | 0" | ✅ Rainfall sufficient |
| Jun | 3.9" | 4.6" | 0" | ✅ Rainfall sufficient |
| Jul | 3.9" | 4.5" | 0" | ✅ Rainfall sufficient |
| Aug | 3.9" | 3.6" | 0.3" | 💧 Light watering |
| Sep | 3.9" | 3.4" | 0.5" | 💧 Light watering |
| Oct | 3.9" | 2.5" | 1.4" | 💧 Light watering |
| Nov | — | 2.6" | 0" | ❄️ Dormant |
| Dec | — | 2" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Brown County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Brussels Sprouts 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.
Brussels Sprouts Planting Timeline — Brown County, IL
Brussels Sprouts Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 13 | Mar 13 – Mar 27 |
| Transplant Outdoors | April 17 | Apr 17 – May 1 |
| Direct Sow | April 3 | Apr 3 – Apr 24 |
| Harvest | July 17 | Jul 17 – Sep 11 |
| Fall Sowing | August 7 | Aug 7 – Aug 21 |
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 | Transplant Outdoors |
| June | — |
| July | Harvest |
| August | Fall Sowing Harvest |
| September | Harvest |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.9"/week · Only during dry spells
📅 Days to Maturity
90–130 days
🧪 Soil pH
Needs 6–7.5 · Your soil: ideal
🗺️ USDA Zone
Zone 5b
📆 Growing Season
182 days in Brown County
Growing Tips for Brussels Sprouts in Brown County
Direct sow Brussels Sprouts outdoors after April 17 in Brown County when soil has warmed and frost danger has passed.
Common pests for Brussels Sprouts 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 12-14 weeks before first fall frost. Stake tall plants to prevent toppling. Remove lower leaves as sprouts develop to improve air circulation.
Companion Planting
Good Companions
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Check more plant combinations with our Companion Planting Checker →
Brussels Sprouts in Other Locations
Frequently Asked Questions
When should I plant Brussels Sprouts in Brown County, IL?
Brown County is in Zone 5b with an average last frost of April 17. Plan your Brussels Sprouts planting based on this frost date — see the calendar above for exact timing.
What planting zone is Brown County, IL?
Brown County, Illinois is in USDA Hardiness Zone 5b. The average last spring frost is April 17 and first fall frost is October 16.
Plan Your Garden with Confidence
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