When to plant Rhubarb in Johnson County, IL
Johnson County sits in cold Zone 7a. Plant Rhubarb April 28–May 12 for the single annual harvest; the October 21 first frost closes the window.
When to Plant Rhubarb in Johnson County, IL
Top priorities for Johnson County, Illinois gardeners in June
A quick June briefing for Johnson County, Illinois gardeners — what's urgent, what's next, and what can wait.
Rhubarb is a long-lived perennial vegetable grown for its tart, colorful stalks. Only the stalks are edible as the leaves contain toxic oxalic acid.
Johnson County, Illinois is in USDA Zone 7a. The average last spring frost is April 7 and the first fall frost is October 21, giving you a growing season of approximately 197 days.
At an elevation of 1,006 feet, Johnson County receives approximately 39.7 inches of rainfall annually with predominantly silt loam soil. Summer highs average 90°F, providing good warmth for Rhubarb during the growing season.
Johnson County Soil Profile
Soil Type
Silt Loam
Soil pH
5.9-7.2
Drainage
Well Drained
Rhubarb 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 Johnson County
How your county's soil matches Rhubarb's growing requirements.
Soil pH
Your soil pH (5.9–7.2) overlaps with Rhubarb's range (6.0–7.0), though not a perfect match.
Soil Texture
The silt loam soil in Johnson County is excellent for Rhubarb — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (4.8%) — Rhubarb will thrive.
How to Plant Rhubarb
Rhubarb Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Rhubarb
Rhubarb needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Rhubarb Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.6" | 0" | ❄️ Dormant |
| Feb | — | 1.9" | 0" | ❄️ Dormant |
| Mar | — | 2.9" | 0" | ❄️ Dormant |
| Apr | 4.3" | 3.6" | 0.7" | 💧 Light watering |
| May | 4.3" | 4.2" | 0.1" | 💧 Light watering |
| Jun | 4.3" | 4.4" | 0" | ✅ Rainfall sufficient |
| Jul | 4.3" | 4.8" | 0" | ✅ Rainfall sufficient |
| Aug | 4.3" | 4.6" | 0" | ✅ Rainfall sufficient |
| Sep | 4.3" | 3.3" | 1" | 💧 Light watering |
| Oct | 4.3" | 3.2" | 1.1" | 💧 Light watering |
| Nov | — | 2.9" | 0" | ❄️ Dormant |
| Dec | — | 2.3" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Johnson County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Rhubarb 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.
Rhubarb Planting Timeline — Johnson County, IL
Rhubarb Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Transplant Outdoors | April 28 | Apr 28 – May 12 |
Plant 1" deep · 30" apart · Rows 42" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | Transplant Outdoors |
| May | Transplant Outdoors |
| June | — |
| July | — |
| August | — |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1"/week · Only during dry spells
📅 Days to Maturity
365–730 days
🧪 Soil pH
Needs 6–7 · Your soil: acceptable
🗺️ USDA Zone
Zone 7a
📆 Growing Season
197 days in Johnson County
Growing Tips for Rhubarb in Johnson County
Direct sow Rhubarb outdoors after April 07 in Johnson County when soil has warmed and frost danger has passed.
Your 197.0-day growing season in Johnson County is tight for Rhubarb (365.0-730.0 days to maturity). Start indoors and choose early-maturing varieties.
General growing tips
Plant crowns in early spring in rich, well-drained soil. Do not harvest stalks the first year. Pull (do not cut) stalks at harvest to avoid introducing rot.
Companion Planting
Good Companions
Check more plant combinations with our Companion Planting Checker →
Rhubarb in Other Locations
Frequently Asked Questions
When should I plant Rhubarb in Johnson County, IL?
Johnson County is in Zone 7a with an average last frost of April 7. Plan your Rhubarb planting based on this frost date — see the calendar above for exact timing.
What planting zone is Johnson County, IL?
Johnson County, Illinois is in USDA Hardiness Zone 7a. The average last spring frost is April 7 and first fall frost is October 21.
When should I plant Rhubarb in Johnson County, IL?
In Johnson County, IL, plant Rhubarb after the last frost (around April 7) and before the first frost (around October 21). Best results when soil holds above 50°F.
What growing zone is Johnson County, IL for Rhubarb?
Johnson County sits in USDA Zone 7a. Rhubarb grows reliably in zones 3a through 8b, so it's a good fit here.
Can Rhubarb grow in Johnson County's climate?
Yes — Rhubarb grows well in Johnson County's temperate climate. Johnson County averages a 197-day frost-free season, with last frost around April 7 and first frost around October 21.
Your Johnson County Garden Planner — Free
A 22-page printable planner built for Johnson County (Zone 7a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.