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When to Plant Romanesco in Walworth County, WI

Walworth County, Wisconsin Zone 5b May

May to-do list for Walworth County, Wisconsin

May rewards gardeners who work with the weather, not against it. Here's how to stay in step this month in Walworth County, Wisconsin.

Avg. last frost April 26
Avg. first frost October 13
Soil temp (4") 56°F
Watering Low
Pest pressure Low
Daylight 14.4 hrs
  1. Begin indoor sowing: romanesco

    A seed-starting mix and a sunny window (or a grow light) are all you need. Keep soil warm — around 70°F — for fast germination.

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Romanesco is a stunning brassica with a lime-green head composed of fractal-patterned spiraling florets. It has a nuttier, milder flavor than cauliflower.

Walworth County, Wisconsin is in USDA Zone 5b. The average last spring frost is April 26 and the first fall frost is October 13, giving you a growing season of approximately 170 days.

At an elevation of 1,101 feet, Walworth County receives approximately 39.6 inches of rainfall annually with predominantly silt loam soil. Summer highs average 87°F, providing good warmth for Romanesco during the growing season.

Walworth County, WI (Zone 5b) Moderate season
170 days
Last Spring Frost April 26
170 growing days
First Fall Frost October 13
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Walworth County Soil Profile

Soil Type

Silt Loam

Soil pH

6.2-6.9

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (50 days to spare)
Start indoors: Mar 18 Transplant: Apr 22 🍅 Harvest: Jul 8 – Aug 19
Recommended (50%) ✓ Fits season (51 days to spare)
Start indoors: Mar 22 Transplant: Apr 26 🍅 Harvest: Jul 12 – Aug 23
Safe Start (90%) ✓ Fits season (49 days to spare)
Start indoors: Apr 7 Transplant: May 12 🍅 Harvest: Jul 28 – Sep 8

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 Walworth County

How your county's soil matches Romanesco's growing requirements.

Soil pH

Your soil pH (6.2–6.9) is within Romanesco's preferred range (6.0–7.0).

Soil Texture

The silt loam soil in Walworth County is excellent for Romanesco — good drainage, moisture retention, and nutrient holding capacity.

Organic Matter

Organic matter is excellent (4.4%) — Romanesco will thrive.

How to Plant Romanesco

1"
Planting Depth
15"
Between Plants
24"
Between Rows

Fall planting: Sow 10 weeks before your first frost date for a fall harvest.

Succession Planting Romanesco

2
successive plantings in your 170-day season

Sow every 8.6 weeks. Last sowing by Jul 05 to harvest before frost.

For a dedicated fall crop, sow by Aug 04.

Plant Water Budget

Plant needs
1.0″/week
Rainfall provides
1.0″/week
You supply
0.0″/week
Watering frequency Only during dry spells
Season total 39 gal / 100 sq ft
Drought risk

Water stress score is 6/10 — consider drought-tolerant varieties and mulching

Monthly Watering Guide for Romanesco

Romanesco needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.

Month Romanesco Needs Rainfall You Supplement Action
Jan 1.9" 0" ❄️ Dormant
Feb 1.8" 0" ❄️ Dormant
Mar 2.5" 0" ❄️ Dormant
Apr 4.3" 3.8" 0.5" 💧 Light watering
May 4.3" 4.2" 0.1" 💧 Light watering
Jun 4.3" 4.7" 0" ✅ Rainfall sufficient
Jul 4.3" 4.9" 0" ✅ Rainfall sufficient
Aug 4.3" 4.1" 0.2" 💧 Light watering
Sep 4.3" 4.2" 0.1" 💧 Light watering
Oct 4.3" 2.9" 1.4" 💧 Light watering
Nov 2.7" 0" ❄️ Dormant
Dec 2" 0" ❄️ Dormant

Water needs are for active growing months only (Apr–Oct in Walworth County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.

Romanesco 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.

Romanesco needs ~1,334 GDD — county provides 2,592 GDD Excellent fit

Romanesco Planting Timeline — Walworth County, WI

Romanesco Planting Calendar

Activity When Date Range
Start Indoors March 22 Mar 22 – Apr 5
Transplant Outdoors April 26 Apr 26 – May 10
Direct Sow April 12 Apr 12 – May 3
Harvest July 12 Jul 12 – Aug 23
Fall Sowing August 4 Aug 4 – Aug 18

Plant 1" deep · 15" apart · Rows 24" apart

Month-by-Month Timeline

MonthActivities
January
February
March Start Indoors
April Start Indoors Transplant Outdoors Direct Sow
May Transplant Outdoors Direct Sow
June
July Harvest
August Fall Sowing Harvest
September
October
November
December
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Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

1"/week · Only during dry spells

📅 Days to Maturity

75–100 days

🧪 Soil pH

Needs 6–7 · Your soil: ideal

🗺️ USDA Zone

Zone 5b

📆 Growing Season

170 days in Walworth County

Growing Tips for Romanesco in Walworth County

Direct sow Romanesco outdoors after April 26 in Walworth County when soil has warmed and frost danger has passed.

Common pests for Romanesco 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 5-7 weeks before transplanting. Provide consistent moisture and avoid temperature stress. Harvest when head is fully formed but before florets begin to separate.

Companion Planting

Good Companions

Avoid Planting Near

  • Tomatoes
  • Strawberries

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Romanesco in Walworth County, WI?

Walworth County is in Zone 5b with an average last frost of April 26. Plan your Romanesco planting based on this frost date — see the calendar above for exact timing.

What planting zone is Walworth County, WI?

Walworth County, Wisconsin is in USDA Hardiness Zone 5b. The average last spring frost is April 26 and first fall frost is October 13.

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Your Walworth County Garden Planner — Free

A 24-page printable planner built for Walworth 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.

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

Sources & credits

Every number on this page traces back to a primary horticulture or government data source. Click through to verify.