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When to Plant Celeriac in Garfield County, MT

Garfield County, Montana Zone 4b May

Your May game plan for Garfield County, Montana

We've pulled the most time-sensitive tasks for Garfield County, Montana this May and put them front and centre. Tackle them in order.

Avg. last frost May 16
Avg. first frost September 21
Soil temp (4") 28°F
Watering High
Pest pressure Low
Daylight 14.9 hrs
  1. Transplant celeriac outside

    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. Direct-sow celeriac

    Rake a smooth bed, make a shallow furrow, drop seeds at the spacing on the packet, water gently, walk away.

Looking ahead to June
  • Starting indoors: celeriac
  • Fall sowing: celeriac

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Celeriac is a celery relative grown for its knobby, flavorful root rather than its stalks. It has a rich celery flavor and is excellent roasted, mashed, or in soups.

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 Celeriac to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing Celeriac successfully. Mulch heavily to conserve soil moisture.

Garfield County, MT (Zone 4b) Short season
128 days
Last Spring Frost May 16
128 growing days
First Fall Frost September 21
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Garfield County Soil Profile

Soil Type

Loam

Soil pH

6.3-7.9

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Mar 29 Transplant: May 10 🍅 Harvest: Aug 23 – Sep 27
Recommended (50%) ✗ May not fit
Start indoors: Apr 4 Transplant: May 16 🍅 Harvest: Aug 29 – Oct 3
Safe Start (90%) ✗ May not fit
Start indoors: Apr 18 Transplant: May 30 🍅 Harvest: Sep 12 – Oct 17

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 Celeriac's growing requirements.

Soil pH

Your soil pH (6.3–7.9) is more alkaline than Celeriac prefers (6.0–7.0). Add sulfur or peat moss to lower pH.

Soil Texture

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

Drainage

Celeriac is a heavy drinker but your soil drains very quickly. Mulch heavily and consider drip irrigation.

Organic Matter

Organic matter is moderate (2.5%). Annual compost additions will help Celeriac.

How to Plant Celeriac

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

Fall planting: Sow 12 weeks before your first frost date for a fall harvest.

Plant Water Budget

Plant needs
0.9″/week
Rainfall provides
0.6″/week
You supply
0.7″/week
Watering frequency 1-2 times/week
Season total 756 gal / 100 sq ft
Drought risk

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

Monthly Watering Guide for Celeriac

Celeriac needs approximately 0.9 inches of water per week (3.9" per month). Here's how your county's rainfall compares month by month.

Month Celeriac 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 3.9" 2.3" 1.6" 💧 Light watering
Jun 3.9" 1.4" 2.5" 🚿 Regular watering
Jul 3.9" 1.5" 2.4" 🚿 Regular watering
Aug 3.9" 2" 1.9" 💧 Light watering
Sep 3.9" 1.8" 2.1" 🚿 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.

Celeriac 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.

Celeriac needs ~1,182 GDD — county provides 1,376 GDD Good fit

Celeriac Planting Timeline — Garfield County, MT

Celeriac Planting Calendar

Activity When Date Range
Start Indoors April 4 Apr 4 – Apr 18
Transplant Outdoors May 16 May 16 – May 30
Direct Sow May 9 May 9 – May 30
Harvest August 29 Aug 29 – Oct 3
Fall Sowing June 29 Jun 29 – Jul 13

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

Month-by-Month Timeline

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

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

0.9"/week · 1-2 times/week

📅 Days to Maturity

100–120 days

🧪 Soil pH

Needs 6–7 · Your soil: too_alkaline

🗺️ USDA Zone

Zone 4b

📆 Growing Season

128 days in Garfield County

Growing Tips for Celeriac in Garfield County

Direct sow Celeriac 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 Celeriac (100.0-120.0 days to maturity). Start indoors and choose early-maturing varieties.

Common pests for Celeriac in this region include carrot rust fly and parsleyworm. Use row covers early in the season and inspect plants weekly.

Garfield County receives only 19" of rain annually. Celeriac needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.

General growing tips

Start seeds indoors 10-12 weeks before last frost. Remove side roots as they develop to encourage a single large bulb. Harvest after a light frost for best flavor.

Companion Planting

Good Companions

Avoid Planting Near

  • Carrots
  • Parsnip

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Celeriac in Garfield County, MT?

Garfield County is in Zone 4b with an average last frost of May 16. Plan your Celeriac 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.

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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 Garfield 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.