When to Plant Rhubarb in Garfield County, MT
Garfield County, Montana gardeners: here's your May plan
May rewards gardeners who work with the weather, not against it. Here's how to stay in step this month in Garfield County, Montana.
Coming up in June — start thinking about
- Transplants going out: rhubarb
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.
Garfield County, Montana is in USDA Zone 4b. The average last spring frost is May 16 and the first fall frost is September 21, giving you a growing season of approximately 128 days.
At an elevation of 8,464 feet, Garfield County receives approximately 18.8 inches of rainfall annually with predominantly loam soil. Summer highs average 81°F, so choose short-season varieties of Rhubarb to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing Rhubarb successfully. Mulch heavily to conserve soil moisture.
Garfield County Soil Profile
Soil Type
Loam
Soil pH
6.3-7.9
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 Garfield County
How your county's soil matches Rhubarb's growing requirements.
Soil pH
Your soil pH (6.3–7.9) is more alkaline than Rhubarb prefers (6.0–7.0). Add sulfur or peat moss to lower pH.
Soil Texture
The loam soil in Garfield County is excellent for Rhubarb — good drainage, moisture retention, and nutrient holding capacity.
Drainage
Drainage is adequate for Rhubarb.
Organic Matter
Organic matter is moderate (2.5%). Annual compost additions will help Rhubarb.
How to Plant Rhubarb
Plant Water Budget
Water stress score is 8/10 — 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 | — | 1.2" | 0" | ❄️ Dormant |
| Feb | — | 1.2" | 0" | ❄️ Dormant |
| Mar | — | 1.7" | 0" | ❄️ Dormant |
| Apr | — | 1.7" | 0" | ❄️ Dormant |
| May | 4.3" | 2.3" | 2" | 💧 Light watering |
| Jun | 4.3" | 1.4" | 2.9" | 🚿 Regular watering |
| Jul | 4.3" | 1.5" | 2.8" | 🚿 Regular watering |
| Aug | 4.3" | 2" | 2.3" | 🚿 Regular watering |
| Sep | 4.3" | 1.8" | 2.5" | 🚿 Regular watering |
| Oct | — | 1.5" | 0" | ❄️ Dormant |
| Nov | — | 1.4" | 0" | ❄️ Dormant |
| Dec | — | 1.1" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Sep in Garfield 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 — Garfield County, MT
Rhubarb Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Transplant Outdoors | June 13 | Jun 13 – Jun 27 |
Plant 1" deep · 30" apart · Rows 42" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | — |
| May | — |
| June | Transplant Outdoors |
| July | — |
| August | — |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1"/week · 2-3 times/week
📅 Days to Maturity
365–730 days
🧪 Soil pH
Needs 6–7 · Your soil: too_alkaline
🗺️ USDA Zone
Zone 4b
📆 Growing Season
128 days in Garfield County
Growing Tips for Rhubarb in Garfield County
Direct sow Rhubarb outdoors after May 16 in Garfield County when soil has warmed and frost danger has passed.
Your 128.0-day growing season in Garfield County is tight for Rhubarb (365.0-730.0 days to maturity). Start indoors and choose early-maturing varieties.
Garfield County receives only 19" of rain annually. Rhubarb needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.
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 Garfield County, MT?
Garfield County is in Zone 4b with an average last frost of May 16. Plan your Rhubarb planting based on this frost date — see the calendar above for exact timing.
What planting zone is Garfield County, MT?
Garfield County, Montana is in USDA Hardiness Zone 4b. The average last spring frost is May 16 and first fall frost is September 21.
Your Garfield County Garden Planner — Free
A 24-page printable planner built for Garfield 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.