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When to Plant Chamomile in Petroleum County, MT

Petroleum County, Montana Zone 4b May

Top priorities for Petroleum County, Montana gardeners in May

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

Avg. last frost May 18
Avg. first frost September 24
Soil temp (4") 30°F
Watering High
Pest pressure Low
Daylight 14.9 hrs
  1. Set out chamomile seedlings

    Pick a cloudy afternoon or evening to plant. Less transplant shock, and your seedlings will barely blink.

  2. Direct-sow chamomile

    These tolerate cool soil, so you're not gambling by sowing now.

Get ahead of June
  • Starting indoors: chamomile

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Chamomile is a daisy-like herb famous for its calming, apple-scented tea. German chamomile is an annual while Roman chamomile is a perennial ground cover.

Petroleum County, Montana is in USDA Zone 4b. The average last spring frost is May 18 and the first fall frost is September 24, giving you a growing season of approximately 129 days.

At an elevation of 8,358 feet, Petroleum County receives approximately 13.7 inches of rainfall annually with predominantly loam soil. Summer highs average 81°F, so choose short-season varieties of Chamomile to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing Chamomile successfully. Mulch heavily to conserve soil moisture.

Petroleum County, MT (Zone 4b) Short season
129 days
Last Spring Frost May 18
129 growing days
First Fall Frost September 24

Petroleum County Soil Profile

Soil Type

Loam

Soil pH

6.8-8.2

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (6 days to spare)
Start indoors: Mar 30 Transplant: May 4 🍅 Harvest: Jul 6 – Sep 14
Recommended (50%) ✓ Fits season (3 days to spare)
Start indoors: Apr 6 Transplant: May 11 🍅 Harvest: Jul 13 – Sep 21
Safe Start (90%) ✓ Fits season (6 days to spare)
Start indoors: Apr 18 Transplant: May 23 🍅 Harvest: Jul 25 – Oct 3

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 Petroleum County

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

Soil pH

Your soil pH (6.8–8.2) overlaps with Chamomile's range (5.6–7.5), though not a perfect match.

Soil Texture

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

Drainage

Drainage is adequate for Chamomile.

Organic Matter

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

How to Plant Chamomile

0.5"
Planting Depth
8"
Between Plants
12"
Between Rows

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

Succession Planting Chamomile

2
successive plantings in your 129-day season

Sow every 6.9 weeks. Last sowing by Jun 26 to harvest before frost.

For a dedicated fall crop, sow by Jul 02.

Plant Water Budget

Plant needs
0.4″/week
Rainfall provides
0.5″/week
You supply
0.1″/week
Watering frequency Only during dry spells
Season total 102 gal / 100 sq ft
Drought risk

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

Monthly Watering Guide for Chamomile

Chamomile needs approximately 0.4 inches of water per week (1.7" per month). Here's how your county's rainfall compares month by month.

Month Chamomile Needs Rainfall You Supplement Action
Jan 1.1" 0" ❄️ Dormant
Feb 0.7" 0" ❄️ Dormant
Mar 1.2" 0" ❄️ Dormant
Apr 1.3" 0" ❄️ Dormant
May 1.7" 1.8" 0" ✅ Rainfall sufficient
Jun 1.7" 0.9" 0.8" 💧 Light watering
Jul 1.7" 1.2" 0.5" 💧 Light watering
Aug 1.7" 1.5" 0.2" 💧 Light watering
Sep 1.7" 1.2" 0.5" 💧 Light 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 Petroleum County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.

Chamomile 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.

Chamomile needs ~806 GDD — county provides 1,386 GDD Excellent fit

Chamomile Planting Timeline — Petroleum County, MT

Chamomile Planting Calendar

Activity When Date Range
Start Indoors April 6 Apr 6 – Apr 20
Transplant Outdoors May 11 May 11 – May 25
Direct Sow May 11 May 11 – Jun 1
Harvest July 13 Jul 13 – Sep 21
Fall Sowing July 2 Jul 2 – Jul 16

Plant 0.5" deep · 8" apart · Rows 12" apart

Month-by-Month Timeline

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

Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

0.4"/week · Only during dry spells

📅 Days to Maturity

60–90 days

🧪 Soil pH

Needs 5.6–7.5 · Your soil: acceptable

🗺️ USDA Zone

Zone 4b

📆 Growing Season

129 days in Petroleum County

Growing Tips for Chamomile in Petroleum County

Direct sow Chamomile outdoors after May 18 in Petroleum County when soil has warmed and frost danger has passed.

Common pests for Chamomile in this region include aphids and slugs. Use row covers early in the season and inspect plants weekly.

General growing tips

Direct sow on the soil surface as seeds need light. Harvest flowers when petals begin to curl back. Chamomile self-sows freely and improves the health of nearby plants.

Companion Planting

Good Companions

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Chamomile in Petroleum County, MT?

Petroleum County is in Zone 4b with an average last frost of May 18. Plan your Chamomile planting based on this frost date — see the calendar above for exact timing.

What planting zone is Petroleum County, MT?

Petroleum County, Montana is in USDA Hardiness Zone 4b. The average last spring frost is May 18 and first fall frost is September 24.

🌱

Your Petroleum County Garden Planner — Free

A 24-page printable planner built for Petroleum 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 Petroleum 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.