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When to Plant Tomatillo in Richland County, MT

Richland County, Montana Zone 4a May

This month in Richland County, Montana

Your Richland County, Montana garden is entering a new phase. Here's what's on the schedule for May and why each task matters now.

Avg. last frost May 14
Avg. first frost September 20
Soil temp (4") 36°F
Watering High
Pest pressure Low
Daylight 14.9 hrs
  1. Outdoor sowing time: tomatillo

    Succession planting is the secret here. Put in a row now, another in 2 weeks, a third in 4.

Before June arrives, get these ready
  • Transplants going out: tomatillo

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Tomatillos are a Mexican staple that produces tart, green fruits enclosed in papery husks. They are essential for salsa verde and green sauces.

Richland County, Montana is in USDA Zone 4a. The average last spring frost is May 14 and the first fall frost is September 20, giving you a growing season of approximately 129 days.

At an elevation of 6,414 feet, Richland County receives approximately 13.6 inches of rainfall annually with predominantly loam soil. Summer highs average 80°F, so choose short-season varieties of Tomatillo to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing Tomatillo successfully. Mulch heavily to conserve soil moisture.

Richland County, MT (Zone 4a) Short season
129 days
Last Spring Frost May 14
129 growing days
First Fall Frost September 20

Richland County Soil Profile

Soil Type

Loam

Soil pH

6.5-7.8

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Mar 8 Transplant: May 31 🍅 Harvest: Aug 2 – Oct 11
Recommended (50%) ✗ May not fit
Start indoors: Mar 12 Transplant: Jun 4 🍅 Harvest: Aug 6 – Oct 15
Safe Start (90%) ✗ May not fit
Start indoors: Mar 28 Transplant: Jun 20 🍅 Harvest: Aug 22 – Oct 31

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 Richland County

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

Soil pH

Your soil pH (6.5–7.8) is more alkaline than Tomatillo prefers (6.0–7.0). Add sulfur or peat moss to lower pH.

Soil Texture

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

Organic Matter

Organic matter is moderate (2.3%). Annual compost additions will help Tomatillo.

How to Plant Tomatillo

1"
Planting Depth
15"
Between Plants
24"
Between Rows

Succession Planting Tomatillo

2
successive plantings in your 129-day season

Sow every 6.9 weeks. Last sowing by Jun 27 to harvest before frost.

Plant Water Budget

Plant needs
1.1″/week
Rainfall provides
0.4″/week
You supply
0.8″/week
Watering frequency 2-3 times/week
Season total 905 gal / 100 sq ft
Drought risk

Water stress score is 8/10 — consider drought-tolerant varieties and mulching

Monthly Watering Guide for Tomatillo

Tomatillo needs approximately 1.1 inches of water per week (4.8" per month). Here's how your county's rainfall compares month by month.

Month Tomatillo Needs Rainfall You Supplement Action
Jan 0.9" 0" ❄️ Dormant
Feb 0.8" 0" ❄️ Dormant
Mar 1.2" 0" ❄️ Dormant
Apr 1.4" 0" ❄️ Dormant
May 4.8" 1.6" 3.2" 🚿 Regular watering
Jun 4.8" 1" 3.8" 🚿 Regular watering
Jul 4.8" 1" 3.8" 🚿 Regular watering
Aug 4.8" 1.6" 3.2" 🚿 Regular watering
Sep 4.8" 1.1" 3.7" 🚿 Regular watering
Oct 1.2" 0" ❄️ Dormant
Nov 1" 0" ❄️ Dormant
Dec 0.7" 0" ❄️ Dormant

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

Tomatillo 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.

Tomatillo needs ~725 GDD — county provides 1,290 GDD Excellent fit

Tomatillo Planting Timeline — Richland County, MT

Tomatillo Planting Calendar

Activity When Date Range
Start Indoors March 12 Mar 12 – Mar 26
Transplant Outdoors June 4 Jun 4 – Jun 18
Direct Sow May 28 May 28 – Jun 18
Harvest August 6 Aug 6 – Oct 15

Plant 1" deep · 15" apart · Rows 24" apart

Month-by-Month Timeline

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

Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

1.1"/week · 2-3 times/week

📅 Days to Maturity

60–85 days

🧪 Soil pH

Needs 6–7 · Your soil: too_alkaline

🗺️ USDA Zone

Zone 4a

📆 Growing Season

129 days in Richland County

Growing Tips for Tomatillo in Richland County

Direct sow Tomatillo outdoors after May 14 in Richland County when soil has warmed and frost danger has passed.

Common pests for Tomatillo in this region include tomato hornworm and aphids. Use row covers early in the season and inspect plants weekly.

Richland County receives only 14" of rain annually. Tomatillo needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.

General growing tips

Start seeds indoors 6-8 weeks before last frost. Plant at least two plants for cross-pollination. Harvest when fruits fill the husk and it begins to split.

Companion Planting

Good Companions

Avoid Planting Near

  • Fennel
  • Dill

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Tomatillo in Richland County, MT?

Richland County is in Zone 4a with an average last frost of May 14. Plan your Tomatillo planting based on this frost date — see the calendar above for exact timing.

What planting zone is Richland County, MT?

Richland County, Montana is in USDA Hardiness Zone 4a. The average last spring frost is May 14 and first fall frost is September 20.

🌱

Your Richland County Garden Planner — Free

A 24-page printable planner built for Richland County (Zone 4a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.

Instant PDF download. No spam, unsubscribe any time.

Data sources: USDA Plant Hardiness Zone Map (2023), NOAA 30-Year Climate Normals. Frost dates are based on 50% probability averages for Richland 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.