When to Plant Spinach in Jefferson County, MT
Spinach is a nutrient-packed cool-season green that grows quickly in spring and fall. It is rich in iron, vitamins, and antioxidants and excellent raw or cooked.
Jefferson County, Montana is in USDA Zone 4b. The average last spring frost is June 15 and the first fall frost is September 7, giving you a growing season of approximately 84 days.
At an elevation of 7,214 feet, Jefferson County receives approximately 21.5 inches of rainfall annually with predominantly loam soil. Summer highs average 82°F, so choose short-season varieties of Spinach to ensure they mature before fall.
Jefferson County Soil Profile
Soil Type
Loam
Soil pH
6.4-7.9
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 Jefferson County
How your county's soil matches Spinach's growing requirements.
Soil pH
Your soil pH (6.4–7.9) overlaps with Spinach's range (6.5–7.5), though not a perfect match.
Soil Texture
The loam soil in Jefferson County is excellent for Spinach — good drainage, moisture retention, and nutrient holding capacity.
Drainage
Drainage is adequate for Spinach.
Organic Matter
Organic matter is moderate (2.5%). Annual compost additions will help Spinach.
How to Plant Spinach
Fall planting: Sow 12 weeks before your first frost date for a fall harvest.
Succession Planting Spinach
Sow every 4 weeks. Last sowing by Jul 19 to harvest before frost.
For a dedicated fall crop, sow by Jun 15.
Plant Water Budget
Water stress score is 8/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Spinach
Spinach needs approximately 0.7 inches of water per week (3" per month). Here's how your county's rainfall compares month by month.
| Month | Spinach Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.5" | 0" | ❄️ Dormant |
| Feb | — | 1.4" | 0" | ❄️ Dormant |
| Mar | — | 2" | 0" | ❄️ Dormant |
| Apr | — | 2" | 0" | ❄️ Dormant |
| May | — | 2.5" | 0" | ❄️ Dormant |
| Jun | 3" | 1.5" | 1.5" | 🚿 Regular watering |
| Jul | 3" | 2" | 1" | 💧 Light watering |
| Aug | 3" | 2" | 1" | 💧 Light watering |
| Sep | 3" | 2" | 1" | 💧 Light watering |
| Oct | — | 1.8" | 0" | ❄️ Dormant |
| Nov | — | 1.4" | 0" | ❄️ Dormant |
| Dec | — | 1.4" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Jun–Sep in Jefferson County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Spinach 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.
Spinach Planting Timeline — Jefferson County, MT
Spinach Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | May 4 | May 4 – May 18 |
| Transplant Outdoors | June 15 | Jun 15 – Jun 29 |
| Direct Sow | June 8 | Jun 8 – Jun 29 |
| Harvest | July 20 | Jul 20 – Sep 21 |
| Fall Sowing | June 15 | Jun 15 – Jun 29 |
Plant 0.5" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | — |
| May | Start Indoors |
| June | Transplant Outdoors Direct Sow Fall Sowing |
| July | Harvest |
| August | Harvest |
| September | Harvest |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Partial Shade (3-6 hours)
💧 Water
0.7"/week · Natural rainfall sufficient
📅 Days to Maturity
35–50 days
🧪 Soil pH
Needs 6.5–7.5 · Your soil: acceptable
🗺️ USDA Zone
Zone 4b
📆 Growing Season
84 days in Jefferson County
Growing Tips for Spinach in Jefferson County
Direct sow Spinach outdoors after June 15 in Jefferson County when soil has warmed and frost danger has passed.
General growing tips
Direct sow as soon as soil can be worked in spring. Plant in partial shade for summer crops to delay bolting. Succession plant every 2 weeks for continuous harvest.
Companion Planting
Good Companions
Check more plant combinations with our Companion Planting Checker →
Wind pollinated — isolate 1/2 mile for purity. Easy to let bolt in heat.
Spinach in Other Locations
Frequently Asked Questions
When should I plant Spinach in Jefferson County, MT?
Jefferson County is in Zone 4b with an average last frost of June 15. Plan your Spinach planting based on this frost date — see the calendar above for exact timing.
What planting zone is Jefferson County, MT?
Jefferson County, Montana is in USDA Hardiness Zone 4b. The average last spring frost is June 15 and first fall frost is September 7.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Jefferson County gardeners in Zone 4b organize planting dates, track what's growing, and never miss a planting window.
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