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When to Plant New Zealand Spinach in Stillwater County, MT

Stillwater County, Montana Zone 5a May

This month in Stillwater County, Montana

A quick May briefing for Stillwater County, Montana gardeners — what's urgent, what's next, and what can wait.

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. Direct-sow new zealand spinach

    Thin ruthlessly once seedlings are up. Crowded roots mean smaller crops from every plant.

Looking ahead to June
  • Transplants going out: new zealand spinach

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New Zealand spinach is a heat-tolerant ground-cover plant with thick, triangular leaves that taste similar to true spinach. It thrives in hot weather when regular spinach bolts.

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 New Zealand Spinach to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing New Zealand Spinach 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 (31 days to spare)
Start indoors: Mar 17 Transplant: May 26 🍅 Harvest: Jul 21 – Aug 18
Recommended (50%) ✓ Fits season (25 days to spare)
Start indoors: Mar 27 Transplant: Jun 5 🍅 Harvest: Jul 31 – Aug 28
Safe Start (90%) ✓ Fits season (25 days to spare)
Start indoors: Apr 15 Transplant: Jun 24 🍅 Harvest: Aug 19 – Sep 16

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 New Zealand Spinach's growing requirements.

Soil pH

Your soil pH (6.3–7.8) overlaps with New Zealand Spinach's range (6.0–7.5), though not a perfect match.

Soil Texture

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

Organic Matter

Organic matter is moderate (2.7%). Annual compost additions will help New Zealand Spinach.

How to Plant New Zealand Spinach

0.5"
Planting Depth
6"
Between Plants
12"
Between Rows

Succession Planting New Zealand Spinach

2
successive plantings in your 123-day season

Sow every 6.3 weeks. Last sowing by Jul 14 to harvest before frost.

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 New Zealand Spinach

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

Month New Zealand Spinach 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.

New Zealand 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.

New Zealand Spinach needs ~766 GDD — county provides 1,506 GDD Excellent fit

New Zealand Spinach Planting Timeline — Stillwater County, MT

New Zealand Spinach Planting Calendar

Activity When Date Range
Start Indoors March 27 Mar 27 – Apr 10
Transplant Outdoors June 5 Jun 5 – Jun 19
Direct Sow May 29 May 29 – Jun 19
Harvest July 31 Jul 31 – Aug 28

Plant 0.5" deep · 6" apart · Rows 12" apart

Month-by-Month Timeline

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

Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

1"/week · 1-2 times/week

📅 Days to Maturity

55–70 days

🧪 Soil pH

Needs 6–7.5 · Your soil: acceptable

🗺️ USDA Zone

Zone 5a

📆 Growing Season

123 days in Stillwater County

Growing Tips for New Zealand Spinach in Stillwater County

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

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

General growing tips

Soak seeds overnight before planting. Direct sow after last frost. Pinch growing tips regularly to encourage bushy growth and tender new leaves.

Companion Planting

Good Companions

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant New Zealand Spinach in Stillwater County, MT?

Stillwater County is in Zone 5a with an average last frost of May 22. Plan your New Zealand Spinach 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.