When to Plant Lavender in Rock County, WI
Your May game plan for Rock County, Wisconsin
May is a pivotal month for Rock County, Wisconsin gardens. Focus on these tasks first and you'll set up the rest of the season for success.
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Plant out lavender
Pinch off the lowest leaves on each seedling before you plant — it reduces water loss while the roots catch up.
Lavender is a fragrant perennial herb with silvery foliage and purple flower spikes. It is prized for its essential oils, culinary uses, and ornamental beauty.
Rock 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 710 feet, Rock County receives approximately 30.4 inches of rainfall annually with predominantly silt loam soil. Summer highs average 86°F, providing good warmth for Lavender during the growing season.
Rock County Soil Profile
Soil Type
Silt Loam
Soil pH
6.2-7.1
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 County
How your county's soil matches Lavender's growing requirements.
Soil pH
Your soil pH (6.2–7.1) overlaps with Lavender's range (6.5–8.0), though not a perfect match.
Soil Texture
The silt loam soil in Rock County is excellent for Lavender — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (5.1%) — Lavender will thrive.
How to Plant Lavender
Plant Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Lavender
Lavender needs approximately 0.3 inches of water per week (1.3" per month). Here's how your county's rainfall compares month by month.
| Month | Lavender Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.3" | 0" | ❄️ Dormant |
| Feb | — | 1.4" | 0" | ❄️ Dormant |
| Mar | — | 2.1" | 0" | ❄️ Dormant |
| Apr | 1.3" | 3.3" | 0" | ✅ Rainfall sufficient |
| May | 1.3" | 3.1" | 0" | ✅ Rainfall sufficient |
| Jun | 1.3" | 3.8" | 0" | ✅ Rainfall sufficient |
| Jul | 1.3" | 3.2" | 0" | ✅ Rainfall sufficient |
| Aug | 1.3" | 3" | 0" | ✅ Rainfall sufficient |
| Sep | 1.3" | 2.8" | 0" | ✅ Rainfall sufficient |
| Oct | 1.3" | 2.6" | 0" | ✅ Rainfall sufficient |
| Nov | — | 2.4" | 0" | ❄️ Dormant |
| Dec | — | 1.5" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Rock County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Lavender 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.
Lavender Planting Timeline — Rock County, WI
Lavender Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Transplant Outdoors | May 3 | May 3 – May 17 |
| Harvest | August 2 | Aug 2 – Oct 18 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | — |
| May | Transplant Outdoors |
| June | — |
| July | — |
| August | Harvest |
| September | Harvest |
| October | Harvest |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.3"/week · Natural rainfall sufficient
📅 Days to Maturity
90–200 days
🧪 Soil pH
Needs 6.5–8 · Your soil: acceptable
🗺️ USDA Zone
Zone 5b
📆 Growing Season
170 days in Rock County
Growing Tips for Lavender in Rock County
Direct sow Lavender outdoors after April 26 in Rock County when soil has warmed and frost danger has passed.
Your 170.0-day growing season in Rock County is tight for Lavender (90.0-200.0 days to maturity). Start indoors and choose early-maturing varieties.
General growing tips
Plant in well-drained, sandy soil. Avoid heavy mulching around the crown. Prune after flowering but do not cut into old wood. Lavender resents wet winter conditions.
Companion Planting
Good Companions
Check more plant combinations with our Companion Planting Checker →
Lavender in Other Locations
Frequently Asked Questions
When should I plant Lavender in Rock County, WI?
Rock County is in Zone 5b with an average last frost of April 26. Plan your Lavender planting based on this frost date — see the calendar above for exact timing.
What planting zone is Rock County, WI?
Rock County, Wisconsin is in USDA Hardiness Zone 5b. The average last spring frost is April 26 and first fall frost is October 13.
Your Rock County Garden Planner — Free
A 24-page printable planner built for Rock 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.