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When to Plant Microgreens in Stillwater County, MT

Stillwater County, Montana Zone 5a May

May to-do list for Stillwater County, Montana

Here's what deserves your attention in Stillwater County, Montana this month. Everything below is tailored to Zone 5a and timed around your local frost dates.

Avg. last frost May 22
Avg. first frost September 22
Soil temp (4") 36°F
Watering High
Pest pressure Low
Daylight 14.7 hrs
  1. Set out microgreens seedlings

    Plant tomatoes deep — bury the stem up to the first true leaves to grow extra roots. Everything else goes in at the same depth it grew in the tray.

  2. Put microgreens seeds straight in the ground

    Mark the row. Birds and stray feet both have opinions about unmarked beds.

  3. Start harvesting microgreens

    Morning harvests are best — cooler temperatures mean crisper produce and longer fridge life.

A few tasks this May that'll pay off in June
  • Starting indoors: microgreens
  • First harvests: microgreens

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Microgreens are young seedlings of vegetables and herbs harvested at the cotyledon or first true leaf stage. They pack concentrated flavors and nutrients in a tiny package.

Stillwater County, Montana is in USDA Zone 5a. The average last spring frost is May 22 and the first fall frost is September 22, giving you a growing season of approximately 123 days.

At an elevation of 6,319 feet, Stillwater County receives approximately 16.6 inches of rainfall annually with predominantly loam soil. Summer highs average 83°F, so choose short-season varieties of Microgreens to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing Microgreens successfully. Mulch heavily to conserve soil moisture.

Stillwater County, MT (Zone 5a) Short season
123 days
Last Spring Frost May 22
123 growing days
First Fall Frost September 22

Stillwater County Soil Profile

Soil Type

Loam

Soil pH

6.3-7.8

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (94 days to spare)
Start indoors: Apr 7 Transplant: May 12 🍅 Harvest: May 19 – Jun 16
Recommended (50%) ✓ Fits season (88 days to spare)
Start indoors: Apr 17 Transplant: May 22 🍅 Harvest: May 29 – Jun 26
Safe Start (90%) ✓ Fits season (88 days to spare)
Start indoors: May 6 Transplant: Jun 10 🍅 Harvest: Jun 17 – Jul 15

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 Stillwater County

How your county's soil matches Microgreens's growing requirements.

Soil pH

Your soil pH (6.3–7.8) is more alkaline than Microgreens prefers (6.0–7.0). Add sulfur or peat moss to lower pH.

Soil Texture

The loam soil in Stillwater County is excellent for Microgreens — good drainage, moisture retention, and nutrient holding capacity.

Organic Matter

Organic matter is moderate (2.7%). Annual compost additions will help Microgreens.

How to Plant Microgreens

0.5"
Planting Depth
2"
Between Plants
6"
Between Rows

Fall planting: Sow 10 weeks before your first frost date for a fall harvest.

Succession Planting Microgreens

24
successive plantings in your 123-day season

Sow every 0.7 weeks. Last sowing by Sep 01 to harvest before frost.

For a dedicated fall crop, sow by Jul 14.

Plant Water Budget

Plant needs
1.0″/week
Rainfall provides
0.6″/week
You supply
0.5″/week
Watering frequency 1-2 times/week
Season total 569 gal / 100 sq ft
Drought risk

Water stress score is 6/10 — consider drought-tolerant varieties and mulching

Monthly Watering Guide for Microgreens

Microgreens needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.

Month Microgreens Needs Rainfall You Supplement Action
Jan 1.1" 0" ❄️ Dormant
Feb 1.1" 0" ❄️ Dormant
Mar 1.5" 0" ❄️ Dormant
Apr 1.8" 0" ❄️ Dormant
May 4.3" 2" 2.3" 🚿 Regular watering
Jun 4.3" 1.1" 3.2" 🚿 Regular watering
Jul 4.3" 1.4" 2.9" 🚿 Regular watering
Aug 4.3" 1.7" 2.6" 🚿 Regular watering
Sep 4.3" 1.4" 2.9" 🚿 Regular watering
Oct 1.4" 0" ❄️ Dormant
Nov 1.1" 0" ❄️ Dormant
Dec 1.1" 0" ❄️ Dormant

Water needs are for active growing months only (May–Sep in Stillwater County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.

Microgreens 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.

Microgreens needs ~172 GDD — county provides 1,506 GDD Excellent fit

Microgreens Planting Timeline — Stillwater County, MT

Microgreens Planting Calendar

Activity When Date Range
Start Indoors April 17 Apr 17 – May 1
Transplant Outdoors May 22 May 22 – Jun 5
Direct Sow May 8 May 8 – May 29
Harvest May 29 May 29 – Jun 26
Fall Sowing July 14 Jul 14 – Jul 28

Plant 0.5" deep · 2" apart · Rows 6" apart

Month-by-Month Timeline

MonthActivities
January
February
March
April Start Indoors
May Start Indoors Transplant Outdoors Direct Sow Harvest
June Transplant Outdoors Harvest
July Fall Sowing
August
September
October
November
December

Growing Conditions

☀️ Sun

Partial Shade (3-6 hours)

💧 Water

1"/week · 1-2 times/week

📅 Days to Maturity

7–21 days

🧪 Soil pH

Needs 6–7 · Your soil: too_alkaline

🗺️ USDA Zone

Zone 5a

📆 Growing Season

123 days in Stillwater County

Growing Tips for Microgreens in Stillwater County

Direct sow Microgreens outdoors after May 22 in Stillwater County when soil has warmed and frost danger has passed.

Your generous 123.0-day season in Stillwater County allows multiple plantings of Microgreens. Sow every 3.0 days for continuous harvest.

Stillwater County receives only 17" of rain annually. Microgreens needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.

General growing tips

Sow seeds densely on shallow trays of moist growing medium. Cover until germination, then provide light. Harvest with scissors when 1-3 inches tall. Grow year-round indoors.

Frequently Asked Questions

When should I plant Microgreens in Stillwater County, MT?

Stillwater County is in Zone 5a with an average last frost of May 22. Plan your Microgreens planting based on this frost date — see the calendar above for exact timing.

What planting zone is Stillwater County, MT?

Stillwater County, Montana is in USDA Hardiness Zone 5a. The average last spring frost is May 22 and first fall frost is September 22.

🌱

Your Stillwater County Garden Planner — Free

A 24-page printable planner built for Stillwater County (Zone 5a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.

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Data sources: USDA Plant Hardiness Zone Map (2023), NOAA 30-Year Climate Normals. Frost dates are based on 50% probability averages for Stillwater County, MT. Local conditions may vary. Last updated: May 2026.

Sources & credits

Every number on this page traces back to a primary horticulture or government data source. Click through to verify.