When to Plant Broccoli in Marathon County, WI
Broccoli is a nutrient-dense cool-season crop that produces large central heads followed by smaller side shoots. It is one of the most popular garden vegetables.
Marathon County, Wisconsin is in USDA Zone 4a. The average last spring frost is May 11 and the first fall frost is October 2, giving you a growing season of approximately 144 days.
At an elevation of 723 feet, Marathon County receives approximately 39.9 inches of rainfall annually with predominantly silt loam soil. Summer highs average 83°F, so choose short-season varieties of Broccoli to ensure they mature before fall.
Marathon County Soil Profile
Soil Type
Silt Loam
Soil pH
6-7.3
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 Marathon County
How your county's soil matches Broccoli's growing requirements.
Soil pH
Your soil pH (6.0–7.3) overlaps with Broccoli's range (6.0–7.0), though not a perfect match.
Soil Texture
The silt loam soil in Marathon County is excellent for Broccoli — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (4.1%) — Broccoli will thrive.
How to Plant Broccoli
Fall planting: Sow 12 weeks before your first frost date for a fall harvest.
Succession Planting Broccoli
Sow every 6.9 weeks. Last sowing by Jul 04 to harvest before frost.
For a dedicated fall crop, sow by Jul 10.
Plant Water Budget
Monthly Watering Guide for Broccoli
Broccoli needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Broccoli Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.7" | 0" | ❄️ Dormant |
| Feb | — | 2" | 0" | ❄️ Dormant |
| Mar | — | 2.7" | 0" | ❄️ Dormant |
| Apr | — | 4.3" | 0" | ❄️ Dormant |
| May | 4.3" | 5" | 0" | ✅ Rainfall sufficient |
| Jun | 4.3" | 4.5" | 0" | ✅ Rainfall sufficient |
| Jul | 4.3" | 4.8" | 0" | ✅ Rainfall sufficient |
| Aug | 4.3" | 4.6" | 0" | ✅ Rainfall sufficient |
| Sep | 4.3" | 3.1" | 1.2" | 💧 Light watering |
| Oct | 4.3" | 3" | 1.3" | 💧 Light watering |
| Nov | — | 2.4" | 0" | ❄️ Dormant |
| Dec | — | 1.9" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Oct in Marathon County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Broccoli 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.
Broccoli Planting Timeline — Marathon County, WI
Broccoli Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 30 | Mar 30 – Apr 13 |
| Transplant Outdoors | May 11 | May 11 – May 25 |
| Direct Sow | May 4 | May 4 – May 25 |
| Harvest | July 13 | Jul 13 – Aug 24 |
| Fall Sowing | July 10 | Jul 10 – Jul 24 |
Plant 1" deep · 15" apart · Rows 24" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | Start Indoors |
| May | Transplant Outdoors Direct Sow |
| June | — |
| July | Fall Sowing Harvest |
| August | Harvest |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1"/week · Natural rainfall sufficient
📅 Days to Maturity
60–90 days
🧪 Soil pH
Needs 6–7 · Your soil: acceptable
🗺️ USDA Zone
Zone 4a
📆 Growing Season
144 days in Marathon County
Growing Tips for Broccoli in Marathon County
Direct sow Broccoli outdoors after May 11 in Marathon County when soil has warmed and frost danger has passed.
Common pests for Broccoli 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 6-8 weeks before last frost. Provide consistent moisture to prevent hollow stems. Harvest heads before yellow flowers appear.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Isolate 1/2 mile from other brassicas. Biennial — must overwinter roots.
Broccoli in Other Locations
Frequently Asked Questions
When should I plant Broccoli in Marathon County, WI?
Marathon County is in Zone 4a with an average last frost of May 11. Plan your Broccoli planting based on this frost date — see the calendar above for exact timing.
What planting zone is Marathon County, WI?
Marathon County, Wisconsin is in USDA Hardiness Zone 4a. The average last spring frost is May 11 and first fall frost is October 2.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Marathon County gardeners in Zone 4a organize planting dates, track what's growing, and never miss a planting window.
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