When to Plant Basil in St. Croix County, WI
May to-do list for St. Croix County, Wisconsin
Your garden in St. Croix County, Wisconsin is working on a schedule, even when you're not. Here's where you should be this May.
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Move basil from tray to bed
Harden off for 7 days — a little more sun each day — before planting. That's the difference between a seedling that thrives and one that stalls.
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Plant basil from seed, right in the garden
Keep the top inch of soil moist until germination — a gentle morning watering for 5–7 days does the job.
Get ahead of June
- Starting indoors: basil
Basil is a fragrant warm-season herb essential to Italian and Thai cuisines. It comes in many varieties including sweet, Thai, purple, and lemon types.
St. Croix County, Wisconsin is in USDA Zone 4b. The average last spring frost is April 28 and the first fall frost is October 9, giving you a growing season of approximately 164 days.
At an elevation of 1,245 feet, St. Croix County receives approximately 38.7 inches of rainfall annually with predominantly silt loam soil. Summer highs average 81°F, so choose short-season varieties of Basil to ensure they mature before fall.
St. Croix County Soil Profile
Soil Type
Silt Loam
Soil pH
6.2-6.7
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 St. Croix County
How your county's soil matches Basil's growing requirements.
Soil pH
Your soil pH (6.2–6.7) is within Basil's preferred range (6.0–7.0).
Soil Texture
The silt loam soil in St. Croix County is excellent for Basil — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (4.8%) — Basil will thrive.
How to Plant Basil
Succession Planting Basil
Sow every 5.7 weeks. Last sowing by Jul 26 to harvest before frost.
Plant Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Basil
Basil needs approximately 0.6 inches of water per week (2.6" per month). Here's how your county's rainfall compares month by month.
| Month | Basil Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.8" | 0" | ❄️ Dormant |
| Feb | — | 1.6" | 0" | ❄️ Dormant |
| Mar | — | 2.8" | 0" | ❄️ Dormant |
| Apr | 2.6" | 4.2" | 0" | ✅ Rainfall sufficient |
| May | 2.6" | 4.9" | 0" | ✅ Rainfall sufficient |
| Jun | 2.6" | 4.2" | 0" | ✅ Rainfall sufficient |
| Jul | 2.6" | 3.7" | 0" | ✅ Rainfall sufficient |
| Aug | 2.6" | 4.6" | 0" | ✅ Rainfall sufficient |
| Sep | 2.6" | 3.4" | 0" | ✅ Rainfall sufficient |
| Oct | 2.6" | 2.8" | 0" | ✅ Rainfall sufficient |
| Nov | — | 2.7" | 0" | ❄️ Dormant |
| Dec | — | 2.1" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in St. Croix County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Basil 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.
Basil Planting Timeline — St. Croix County, WI
Basil Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 3 | Mar 3 – Mar 17 |
| Transplant Outdoors | May 19 | May 19 – Jun 2 |
| Direct Sow | May 5 | May 5 – May 26 |
| Harvest | July 14 | Jul 14 – Sep 15 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | — |
| May | Transplant Outdoors Direct Sow |
| June | Transplant Outdoors |
| July | Harvest |
| August | Harvest |
| September | Harvest |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.6"/week · Natural rainfall sufficient
📅 Days to Maturity
50–75 days
🧪 Soil pH
Needs 6–7 · Your soil: ideal
🗺️ USDA Zone
Zone 4b
📆 Growing Season
164 days in St. Croix County
Growing Tips for Basil in St. Croix County
Direct sow Basil outdoors after April 28 in St. Croix County when soil has warmed and frost danger has passed.
General growing tips
Start seeds indoors or direct sow after last frost. Pinch flower buds to extend leaf production. Harvest leaves from the top down, cutting just above a leaf pair.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Isolate 150 ft between varieties. Different basil species can cross.
Basil in Other Locations
Frequently Asked Questions
When should I plant Basil in St. Croix County, WI?
St. Croix County is in Zone 4b with an average last frost of April 28. Plan your Basil planting based on this frost date — see the calendar above for exact timing.
What planting zone is St. Croix County, WI?
St. Croix County, Wisconsin is in USDA Hardiness Zone 4b. The average last spring frost is April 28 and first fall frost is October 9.
Your St. Croix County Garden Planner — Free
A 24-page printable planner built for St. Croix County (Zone 4b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.