Petroleum County, MT — Planting Guide
May to-do list for Petroleum County, Montana
May rewards gardeners who work with the weather, not against it. Here's how to stay in step this month in Petroleum County, Montana.
-
Transplant kale, lettuce, and angelica outside
Bring a watering can to the bed. Each transplant gets a drink the moment it's in the ground, not ten minutes later.
-
Scatter basil, carrots, and kale into prepared beds
Your soil is 30°F — warm enough for these to germinate without babying.
-
Collect microgreens at their peak
Don't tug. Use scissors or pruners for clean cuts — torn stems invite disease.
Before June arrives, get these ready
- Transplants going out: basil, cucumber, and peppers
- Direct-sowing: cucumber, green beans, and peppers
- Starting indoors: cucumber, kale, and lettuce
- First harvests: lettuce, radish, and arugula
Petroleum County 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 ft, Petroleum County receives approximately 13.7 in of rainfall annually. Summer highs average 81°F with winter lows around 6°F. The predominant soil type is Loam.
Based on 31 years of NOAA climate station data, the last frost date here varies by 26 days year to year — ranging from May 4 in warm years to May 30 in cold years. The growing season is trending longer by about 2.73 days per decade. Petroleum County scores 28/100 (Challenging) on the Microclimate Index.
🌡️ Zone
4b (°F to °F min)
❄️ Last Frost
May 18
🍂 First Frost
September 24
📅 Growing Season
129 days
⛰️ Elevation
8,358 ft
🌧️ Annual Rainfall
13.7 in
Monthly Watering Calendar
When you'll need to water your garden — based on average monthly rainfall vs. the ~1 inch/week most gardens need.
View detailed monthly data
| Month | Avg Rainfall | Rainy Days | Extra Water Needed | Watering Effort |
|---|---|---|---|---|
| Jan | 1.1 in | 7 days | — | None |
| Feb | 0.7 in | 6 days | — | None |
| Mar | 1.2 in | 7 days | — | None |
| Apr | 1.3 in | 7 days | 3 in | High |
| May | 1.8 in | 6 days | 2.5 in | High |
| Jun | 0.9 in | 5 days | 3.4 in | Critical |
| Jul | 1.2 in | 6 days | 3.1 in | Critical |
| Aug | 1.5 in | 7 days | 2.8 in | High |
| Sep | 1.2 in | 5 days | 3.1 in | Critical |
| Oct | 1.2 in | 6 days | 3.1 in | Critical |
| Nov | 1 in | 6 days | — | None |
| Dec | 0.7 in | 6 days | — | None |
Annual total: 13.8 in. Water needs vary by crop — tomatoes need ~1.2"/week while herbs like rosemary need only 0.3"/week. Check individual plant pages for crop-specific water budgets that factor in your county's rainfall and soil drainage.
Petroleum County Soil Profile
Soil Type
Loam
Soil pH
6.8-8.2
Drainage
Well Drained
Frost Risk Probability
Based on 31 years of NOAA weather station data from 3 stations
Beginners: Plant frost-sensitive crops (tomatoes, peppers, squash) after the "Safe" date on the left. Harvest or cover them before the "Protect by" date on the right. Hardy crops (lettuce, peas, kale) can go in the yellow transition zones.
How to read this table: "Conservative" means you're safe from frost 9 out of 10 years — best for beginners and frost-sensitive crops. "Average year" is the typical date. "Aggressive" means only 1 in 10 years is that warm — experienced gardeners with frost protection can try these dates.
| Planting Strategy | Last Spring Frost | First Fall Frost | Frost-Free Days |
|---|---|---|---|
| Conservative (safest) | May 30 | Oct 9 | 132 days |
| Cautious | May 22 | Oct 3 | 134 days |
| Average year | May 18 | Sep 24 | 129 days |
| Optimistic | May 11 | Sep 20 | 132 days |
| Aggressive (risky) | May 4 | Sep 11 | 130 days |
Not very — frost dates can vary by ±26 days year-to-year. Use the "Conservative" row in the table below, and keep row covers handy for surprise late frosts.
Yes — growing seasons are getting longer here (about 2.7 days per decade). Spring is arriving earlier than it used to. Good news for gardeners.
Gardening Difficulty Score
Petroleum County has challenging growing conditions. Season extension and careful variety selection are essential.
Local Gardening Help in Petroleum County
Free expert help is closer than you think. Your county's cooperative extension office connects you with trained gardeners, soil testing labs, and local programs — all specific to Petroleum County's climate and soil.
County Extension Office
Petroleum County Montana State University Extension Extension Office
Phone: 406-994-3402
Visit Extension Office Website →
Extension offices are run by land-grant universities and funded by the USDA. Their advice is free, research-based, and tailored to your county's specific conditions.
Master Gardener Program
Free gardening help from trained volunteers
Master Gardeners are community volunteers who complete 40–60 hours of university horticultural training. They answer gardening questions, diagnose plant problems, and offer workshops — all free.
Many extension offices run a Master Gardener hotline where you can call or email with photos of plant problems for free diagnosis.
Soil Testing
Available through your extension office
Before amending your soil, get it tested. Your extension office offers soil testing (typically $10–$25) that tells you exact pH, nutrient levels, and amendment recommendations specific to what you want to grow.
Services Available in Petroleum County
Finding local nurseries & garden centers in Petroleum County
Why Buy Local
Local nurseries carry plants that are proven to grow in your area. Staff can give you advice specific to Petroleum County's soil and climate that big-box stores can't. Plants from local growers are typically hardier because they're already acclimated to your zone.
How to Find Them
Search for "nurseries near Petroleum County MT" or "garden center Petroleum County" on Google Maps. Also check with your extension office — they often maintain lists of reputable local nurseries and plant sales.
Community gardens & gardening groups
Community gardens are a great way to learn from experienced gardeners in your area, especially if you're limited on space. Search "community garden Petroleum County MT" or check your extension office and local parks department. Facebook groups like "Petroleum County Gardeners" or "Montana Gardening" are also excellent for local advice and plant swaps.
What to Plant After Your Harvest
After your first crops finish, use the remaining frost-free days to grow a second round.
Show 6 more succession options
Sunlight & Day Length
Monthly daylight hours and peak sun — critical for onion varieties, photoperiod-sensitive plants, and solar garden planning.
Longest Day
15.7 hours
Summer solstice daylight
Shortest Day
8.3 hours
Winter solstice daylight
Peak Sun Hours
11.3 hr/day peak (summer)
Peak sun hours (green dashed line below) account for cloud cover — this is the usable direct sunlight your garden actually receives. Most vegetables need 6+ peak sun hours.
Onion tip: Your long summer days (14+ hours) support long-day onion varieties like Walla Walla, Sweet Spanish, and Ailsa Craig.
View detailed monthly data
| Month | Daylight Hours | Peak Sun Hours | Day Length |
|---|---|---|---|
| January | 8.7 hr | 5 hr | Short day |
| February | 10 hr | 5.9 hr | Short day |
| March | 11.6 hr | 6.7 hr | Short day |
| April | 13.4 hr | 8 hr | Neutral |
| May | 14.9 hr | 9.2 hr | Long day |
| June | 15.7 hr | 11.3 hr | Long day |
| July | 15.3 hr | 10.3 hr | Long day |
| August | 14 hr | 9.4 hr | Long day |
| September | 12.3 hr | 9 hr | Neutral |
| October | 10.6 hr | 6.6 hr | Short day |
| November | 9.1 hr | 5.2 hr | Short day |
| December | 8.3 hr | 4.8 hr | Short day |
Peak sun hours factor in typical cloud cover — use these for solar panel and shade-planning calculations.
Soil Temperature & Composting Calendar
Monthly soil temps tell you when to plant warm-season crops, and when your compost pile is actively working.
Plant Warm Crops When
Soil reaches 60°F+
Soil rarely reaches 60°F — use black plastic mulch to warm soil.
Best Month to Compost
Apr
Microbial activity peaks when soil is warm.
Active Composting
0 months
Short season — insulate pile or use indoor vermicomposting.
View detailed monthly data
| Month | Soil 4" Deep | Soil 8" Deep | Compost Activity | Time to Finish |
|---|---|---|---|---|
| Jan | -10°F | -2°F | ❄️ Dormant | ~36 weeks |
| Feb | -11°F | -3°F | ❄️ Dormant | ~36 weeks |
| Mar | -0°F | 3°F | ❄️ Dormant | ~36 weeks |
| Apr | 13°F | 13°F | ❄️ Dormant | ~36 weeks |
| May | 30°F | 23°F | ❄️ Dormant | ~36 weeks |
| Jun | 38°F | 35°F | ❄️ Dormant | ~36 weeks |
| Jul | 46°F | 41°F | 🐢 Slow | ~24 weeks |
| Aug | 48°F | 43°F | 🐢 Slow | ~24 weeks |
| Sep | 40°F | 38°F | 🐢 Slow | ~24 weeks |
| Oct | 26°F | 29°F | ❄️ Dormant | ~36 weeks |
| Nov | 12°F | 18°F | ❄️ Dormant | ~36 weeks |
| Dec | -5°F | 4°F | ❄️ Dormant | ~36 weeks |
Highlighted rows = soil 60°F+ (safe for warm-season transplants). Compost finishes fastest during peak activity months.
Pest & Disease Pressure in Petroleum County
Computed from local climate patterns — warmer, humid conditions increase pest generations and fungal disease risk.
Insect Pest Pressure
Moderate — common pests appear but manageable with monitoring.
Disease Risk
Low disease risk — dry conditions reduce fungal problems.
Seasonal Risk
View 5 common pests in your area
| Pest | Risk Level | Peak Months |
|---|---|---|
| Aphids | Moderate | May, Jun, Jul, Aug |
| Cabbage worms | Moderate | Jun, Jul, Aug |
| Colorado potato beetle | Low | Jun, Jul |
| Flea beetles | Low | May, Jun, Jul |
| Slugs | Low | May, Jun, Jul, Aug, Sep |
Organic pest management tips
- Maintain healthy soil with regular compost additions to build natural pest resistance
- Practice crop rotation annually to break pest cycles
- Encourage beneficial insects with flowering herbs like dill, fennel, and yarrow
Cover Crops for Petroleum County
Cover crops protect bare soil, fix nitrogen, suppress weeds, and improve soil structure — with county-specific planting dates.
Spring Cover Crops (2 options) — Build soil before the main growing season
| Crop | Plant By | Terminate | N-Fixing | Soil Benefit |
|---|---|---|---|---|
| Buckwheat | May 23 | Jul 23 | — | Rapid growth, attracts pollinators, suppresses weeds |
| White clover | Apr 23 | Jul 23 | ✓ Yes | Living mulch, fixes nitrogen, permanent ground cover |
Summer Cover Crops (1 options) — Fill gaps and suppress weeds between plantings
| Crop | Plant By | Terminate | N-Fixing | Soil Benefit |
|---|---|---|---|---|
| Sunflowers | Jun 3 | Aug 27 | — | Deep roots break compaction, attract pollinators and beneficial insects |
Fall Cover Crops (5 options) — Plant after harvest to protect soil over winter
| Crop | Plant By | Terminate | N-Fixing | Soil Benefit |
|---|---|---|---|---|
| Daikon radish | Aug 10 | May 4 | — | Deep taproot breaks compaction, excellent for clay soils |
| Hairy vetch | Jul 6 | May 4 | ✓ Yes | Excellent nitrogen fixer, good for depleted soils |
| Oats | Aug 19 | Apr 27 | — | Quick biomass, winterkills in cold zones — no spring tillage needed |
| Winter rye | Jun 16 | Apr 27 | — | Suppresses weeds, prevents erosion, breaks up compacted soil |
| Winter wheat | Jul 2 | Apr 27 | — | Erosion control, weed suppression, good biomass |
Wind & Microclimate
Wind dries soil, stresses plants, and affects frost patterns. Understanding your exposure helps with garden placement.
Seasonal Wind Speed
Spring: 16 mph Summer: 11 mph
Fall: 11 mph Winter: 16 mph
Prevailing wind: W. Windy area — plant a windbreak hedge on the W side of your garden.
Windbreak Benefit
7/10
Strongly recommended — a windbreak (fence, hedge, or row of tall crops like corn or sunflowers) will significantly improve garden yields.
Frost Pocket Risk
High
Hilly terrain with 1,821 ft of elevation range — cold air pools in low spots. Avoid planting frost-sensitive crops in valleys.
Rainwater Harvesting Potential
How much water you can collect, when to collect it, and what size system you need for your garden.
Annual Collection
6,877 gal
Per 1,000 sq ft of roof area (at 80% collection efficiency)
Recommended Setup
8 rain barrels (55 gal each)
For a typical 500 sq ft garden. Serious collectors: consider a 2,000 gal tank.
Legal Status
Unrestricted
Rainwater harvesting is fully legal in your state with no restrictions.
Best Collection Months
Mar, Apr, May, Aug
Highest rainfall months — your barrels will fill up quickly during these months.
Months to Draw From Storage
Feb, Jun, Dec
Dry months when you'll rely on stored water — size your storage for this gap.
Rainwater collection tips for your area
- Your county receives approximately 13.8 inches of rain per year
- A 1,000 sq ft roof can collect roughly 6,877 gallons annually
- Rainwater harvesting is fully legal in your state
- In your dry climate, every drop counts — consider a larger cistern system
- Position collection tanks in shade to reduce evaporation and algae growth
Soil & Growing Conditions in Petroleum County
Soil Type
Loam
Soil pH 6.8–8.2 · Excessively Drained drainage
Native soil is well-suited to most vegetables and herbs with regular compost additions.
Watering Needs
Drought stress: 5.5/10
Moderate drought pressure. Drip irrigation and mulching are highly recommended to maintain soil moisture through summer.
Season Tips
129-day frost-free season
A short season means indoor starts are critical for warm-season crops. Prioritise cold-hardy, fast-maturing varieties and use row covers to extend autumn harvests.
Your Free Printable Garden Planner
Plan every bed, every planting, every harvest — in one place. This 24-page printable includes your zone's planting calendar, a month-by-month task list, a seed inventory tracker, a harvest log, and succession-planting charts. Built to print, write in, and actually use all season.
Recommended for Your Garden
Test your soil pH, nitrogen, phosphorus, and potassium levels before planting.
Get instant, accurate soil pH readings to fine-tune your amendments.
Boost soil fertility and structure with rich, well-aged organic compost.
🥬 Vegetables to Grow in Petroleum County
96 vegetables that grow well in Zone 4b with planting dates for Petroleum County.
Show all 96 vegetables with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Harvest | Days to Maturity |
|---|---|---|---|---|---|
| Acorn Squash | Apr 6 | Jun 1 | Jun 8 | Aug 31 – Oct 5 | 80–100 |
| Amaranth | Mar 16 | Jun 1 | Jun 8 | Sep 7 – Oct 26 | 90–120 |
| Arugula | Apr 6 | May 11 | May 18 | Jun 22 – Aug 24 | 30–50 |
| Asparagus | — | — | Jun 1 | — | 730–1095 |
| Beets | — | May 11 | — | Jul 6 – Aug 3 | 50–70 |
| Belgian Endive | Apr 6 | May 11 | May 18 | Sep 7 – Oct 12 | 110–150 |
| Black Beans | — | Jun 1 | — | Aug 31 – Oct 19 | 90–120 |
| Bok Choy | Apr 6 | May 11 | May 18 | Jun 29 – Aug 3 | 40–60 |
| Broccoli | Apr 6 | May 11 | May 18 | Jul 20 – Aug 31 | 60–90 |
| Broccoli Rabe | Apr 6 | May 11 | May 18 | Jun 29 – Aug 3 | 40–60 |
| Brussels Sprouts | Apr 6 | May 11 | May 18 | Aug 17 – Oct 12 | 90–130 |
| Butternut Squash | Apr 6 | Jun 1 | Jun 8 | Sep 7 – Oct 12 | 85–110 |
| Cabbage | Apr 6 | May 11 | May 18 | Jul 20 – Sep 14 | 60–100 |
| Carrots | — | May 11 | — | Jul 13 – Aug 17 | 60–80 |
| Cauliflower | Apr 6 | May 11 | May 18 | Jul 13 – Sep 14 | 55–100 |
| Celeriac | Apr 6 | May 11 | May 18 | Aug 31 – Oct 5 | 100–120 |
| Celery | Apr 6 | May 11 | May 18 | Aug 10 – Oct 5 | 80–120 |
| Celtuce | Apr 6 | May 11 | May 18 | Jul 20 – Aug 31 | 60–90 |
| Chard | Apr 6 | May 11 | May 18 | Jul 13 – Aug 31 | 50–60 |
| Chickpeas | Apr 6 | May 11 | May 18 | Aug 10 – Sep 21 | 80–110 |
| Chicory | Apr 6 | May 11 | May 18 | Jul 20 – Aug 31 | 60–85 |
| Chinese Cabbage | Apr 6 | May 11 | May 18 | Jul 13 – Aug 10 | 50–70 |
| Christmas Lima Beans | Mar 16 | Jun 1 | Jun 8 | Aug 31 – Oct 5 | 80–100 |
| Collard Greens | Apr 6 | May 11 | May 18 | Jul 13 – Sep 14 | 55–75 |
| Corn | — | Jun 1 | — | Aug 3 – Sep 28 | 60–100 |
| Cress | Apr 6 | May 11 | May 18 | Jun 1 – Jun 22 | 14–21 |
| Crookneck Squash | Apr 6 | Jun 1 | Jun 8 | Jul 27 – Aug 24 | 45–60 |
| Crosne | — | May 11 | — | Oct 12 – Oct 5 | 150–200 |
| Cucumber | Apr 6 | Jun 1 | Jun 8 | Aug 3 – Sep 28 | 50–70 |
| Daikon | — | May 11 | — | Jul 6 – Aug 3 | 50–70 |
| Delicata Squash | Apr 6 | Jun 1 | Jun 8 | Aug 31 – Oct 5 | 80–100 |
| Edamame | — | Jun 1 | — | Aug 17 – Sep 28 | 75–100 |
| Endive | Apr 6 | May 11 | May 18 | Jul 6 – Aug 10 | 45–65 |
| Escarole | Apr 6 | May 11 | May 18 | Jul 13 – Aug 10 | 50–70 |
| Fava Beans | Apr 6 | May 11 | May 18 | Aug 3 – Sep 14 | 75–100 |
| Fennel | Mar 16 | Jun 1 | Jun 8 | Aug 10 – Sep 21 | 60–90 |
| Garlic | — | — | — | — | 90–240 |
| Green Beans | — | Jun 1 | — | Jul 27 – Sep 21 | 50–65 |
| Horseradish | — | — | Jun 1 | Oct 5 – Oct 26 | 120–180 |
| Hubbard Squash | Apr 6 | Jun 1 | Jun 8 | Sep 21 – Oct 26 | 100–120 |
| Kabocha | Apr 6 | Jun 1 | Jun 8 | Sep 7 – Oct 5 | 85–100 |
| Kai Lan | Apr 6 | May 11 | May 18 | Jul 6 – Aug 3 | 45–60 |
| Kale | Apr 6 | May 11 | May 18 | Jul 13 – Sep 7 | 50–70 |
| Kidney Beans | — | Jun 1 | — | Aug 31 – Oct 5 | 85–110 |
| Kohlrabi | Apr 6 | May 11 | May 18 | Jul 6 – Aug 10 | 45–65 |
| Komatsuna | Apr 6 | May 11 | May 18 | Jun 22 – Jul 27 | 35–50 |
| Leeks | Apr 6 | May 11 | May 18 | Aug 17 – Oct 12 | 90–150 |
| Lentils | Apr 6 | May 11 | May 18 | Aug 10 – Sep 21 | 80–110 |
| Lettuce | Apr 6 | May 11 | May 18 | Jun 22 – Aug 31 | 30–60 |
| Lima Beans | — | Jun 1 | — | Aug 3 – Sep 14 | 60–90 |
| Mache | Apr 6 | May 11 | May 18 | Jun 29 – Aug 3 | 40–60 |
| Melon | Apr 6 | Jun 1 | Jun 8 | Aug 17 – Oct 5 | 70–100 |
| Microgreens | Apr 6 | May 11 | May 18 | May 25 – Jun 22 | 7–21 |
| Mitsuba | Apr 6 | May 11 | May 11 | Jul 6 – Aug 31 | 50–70 |
| Mizuna | Apr 6 | May 11 | May 18 | Jun 22 – Jul 20 | 30–45 |
| Mustard Greens | Apr 6 | May 11 | May 18 | Jun 22 – Aug 24 | 30–50 |
| Napa Cabbage | Apr 6 | May 11 | May 18 | Jul 13 – Aug 17 | 55–75 |
| Onion | Apr 6 | May 11 | May 18 | Aug 17 – Oct 5 | 90–120 |
| Pac Choi | Apr 6 | May 11 | May 18 | Jun 29 – Jul 27 | 40–55 |
| Parsnip | — | May 11 | — | Aug 24 – Oct 5 | 100–130 |
| Patty Pan Squash | Apr 6 | Jun 1 | Jun 8 | Jul 27 – Aug 24 | 45–60 |
| Peas | Apr 6 | May 11 | May 18 | Jul 13 – Sep 7 | 55–70 |
| Peppers | Mar 2 | Jun 1 | Jun 8 | Aug 10 – Oct 19 | 60–90 |
| Pole Beans | Mar 16 | Jun 1 | Jun 8 | Aug 3 – Sep 28 | 55–70 |
| Potatoes | Mar 16 | Jun 1 | Jun 8 | Aug 17 – Oct 26 | 70–120 |
| Pumpkin | Apr 6 | Jun 1 | Jun 8 | Sep 7 – Oct 26 | 85–120 |
| Purslane | Apr 6 | May 11 | May 18 | Jun 29 – Aug 3 | 40–60 |
| Radicchio | Apr 6 | May 11 | May 18 | Jul 20 – Aug 24 | 60–80 |
| Radish | — | May 11 | — | Jun 8 – Jun 29 | 22–35 |
| Rhubarb | — | — | Jun 15 | — | 365–730 |
| Romanesco | Apr 6 | May 11 | May 18 | Aug 3 – Sep 14 | 75–100 |
| Rutabaga | — | May 11 | — | Aug 3 – Sep 7 | 80–100 |
| Salsify | — | May 11 | — | Aug 24 – Oct 5 | 100–130 |
| Savoy Cabbage | Apr 6 | May 11 | May 18 | Jul 27 – Sep 21 | 70–110 |
| Scallions | Apr 6 | May 11 | May 18 | Jul 13 – Aug 10 | 50–70 |
| Scarlet Runner Beans | Mar 16 | Jun 1 | Jun 8 | Aug 10 – Sep 14 | 60–80 |
| Shallot | Apr 6 | May 11 | May 18 | Aug 17 – Oct 5 | 90–120 |
| Shiso | Mar 23 | May 25 | Jun 8 | Aug 3 – Sep 28 | 50–70 |
| Snap Peas | Mar 16 | Jun 1 | Jun 8 | Aug 3 – Sep 28 | 55–70 |
| Snow Peas | Apr 6 | May 11 | May 18 | Jul 13 – Sep 7 | 50–65 |
| Soybeans | — | Jun 1 | — | Aug 24 – Oct 19 | 80–120 |
| Spaghetti Squash | Apr 6 | Jun 1 | Jun 8 | Sep 7 – Oct 5 | 85–100 |
| Spinach | Apr 6 | May 11 | May 18 | Jun 22 – Aug 24 | 35–50 |
| Squash (Summer) | Apr 6 | Jun 1 | Jun 8 | Jul 27 – Sep 28 | 45–65 |
| Squash (Winter) | Apr 6 | Jun 1 | Jun 8 | Aug 31 – Oct 26 | 80–120 |
| Sunchoke | — | — | Jun 1 | Sep 21 – Oct 26 | 110–150 |
| Sunflower | Mar 16 | Jun 1 | Jun 8 | Aug 17 – Oct 5 | 70–100 |
| Sweet Corn | — | Jun 1 | — | Aug 3 – Sep 14 | 60–90 |
| Tatsoi | Apr 6 | May 11 | May 18 | Jun 22 – Jul 27 | 35–50 |
| Tomatillo | Mar 16 | Jun 1 | Jun 8 | Aug 10 – Oct 19 | 60–85 |
| Tomatoes | Mar 16 | Jun 1 | Jun 8 | Aug 10 – Oct 19 | 60–85 |
| Turnip | — | May 11 | — | Jun 22 – Jul 27 | 40–60 |
| Watercress | Apr 6 | May 11 | May 18 | Jun 29 – Aug 3 | 40–60 |
| Watermelon | Apr 6 | Jun 1 | Jun 8 | Aug 17 – Oct 5 | 70–100 |
| Wax Beans | — | Jun 1 | — | Jul 27 – Sep 21 | 50–65 |
| Zucchini | Apr 6 | Jun 1 | Jun 8 | Jul 27 – Sep 21 | 45–60 |
🍓 Fruits to Grow in Petroleum County
22 fruits that grow well in Zone 4b with planting dates for Petroleum County.
Show all 22 fruits with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Harvest | Days to Maturity |
|---|---|---|---|---|---|
| Alpine Strawberries | — | — | Jun 15 | Sep 14 – Nov 9 | 90–180 |
| Aronia | — | — | Jun 15 | — | 730–1095 |
| Blueberries | — | — | Jun 15 | — | 730–1095 |
| Cantaloupe | — | — | Jun 15 | Aug 24 – Sep 28 | 70–90 |
| Cranberries | — | — | Jun 15 | — | 730–1095 |
| Currants | — | — | Jun 15 | — | 730–1095 |
| Elderberries | — | — | Jun 15 | — | 730–1095 |
| Goji Berries | — | — | Jun 15 | — | 730–1095 |
| Gooseberries | — | — | Jun 15 | — | 730–1095 |
| Grapes | — | — | Jun 15 | — | 730–1095 |
| Ground Cherry | — | — | Jun 15 | Aug 24 – Oct 19 | 65–80 |
| Hardy Kiwi | — | — | Jun 15 | — | 1095–1825 |
| Haskaps | — | — | Jun 15 | — | 730–1095 |
| Honeydew | — | — | Jun 15 | Sep 7 – Oct 19 | 80–110 |
| Jostaberry | — | — | Jun 15 | — | 730–1095 |
| Lingonberries | — | — | Jun 15 | — | 730–1095 |
| Medlar | — | — | Jun 15 | — | 1095–1825 |
| Mulberries | — | — | Jun 15 | — | 730–1825 |
| Persimmon | — | — | Jun 15 | — | 1095–2555 |
| Raspberries | — | — | Jun 15 | — | 365–730 |
| Serviceberries | — | — | Jun 15 | — | 730–1095 |
| Strawberries | — | — | Jun 15 | Sep 14 – Nov 9 | 90–365 |
🌿 Herbs to Grow in Petroleum County
32 herbs that grow well in Zone 4b with planting dates for Petroleum County.
Show all 32 herbs with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Harvest | Days to Maturity |
|---|---|---|---|---|---|
| Angelica | Apr 6 | May 11 | May 11 | — | 365–730 |
| Anise | Apr 6 | May 11 | May 11 | Aug 10 – Oct 5 | 90–120 |
| Basil | Mar 23 | May 25 | Jun 8 | Aug 3 – Oct 5 | 50–75 |
| Bee Balm | — | — | May 25 | Aug 24 – Oct 19 | 90–120 |
| Borage | Apr 6 | May 11 | May 11 | Jul 6 – Aug 24 | 50–60 |
| Caraway | Apr 6 | May 11 | May 11 | — | 365–450 |
| Catnip | — | — | May 25 | Jul 27 – Sep 28 | 60–80 |
| Chamomile | Apr 6 | May 11 | May 11 | Jul 13 – Sep 21 | 60–90 |
| Chervil | Apr 6 | May 11 | May 11 | Jun 22 – Aug 24 | 40–60 |
| Chives | — | — | May 25 | Jul 27 – Oct 5 | 60–90 |
| Cilantro | Apr 6 | May 11 | May 11 | Jun 22 – Aug 24 | 40–60 |
| Comfrey | — | — | May 25 | Jul 27 – Oct 5 | 60–90 |
| Dill | Apr 6 | May 11 | May 11 | Jun 22 – Aug 24 | 40–60 |
| Echinacea | — | — | May 25 | Sep 28 – Oct 19 | 120–180 |
| Fennel (herb) | Apr 6 | May 11 | May 11 | Jul 13 – Sep 21 | 60–90 |
| Garlic Chives | — | — | May 25 | Jul 27 – Oct 5 | 60–90 |
| Horehound | — | — | May 25 | Aug 10 – Oct 5 | 75–90 |
| Hyssop | — | — | May 25 | Aug 3 – Oct 5 | 70–90 |
| Lemon Balm | — | — | May 25 | Jul 27 – Sep 14 | 60–70 |
| Lovage | — | — | May 25 | Aug 3 – Oct 5 | 70–90 |
| Mint | — | — | May 25 | Jul 27 – Oct 5 | 60–90 |
| Oregano | — | — | May 25 | Jul 27 – Oct 5 | 60–90 |
| Parsley | Apr 6 | May 11 | May 11 | Jul 13 – Sep 14 | 60–80 |
| Rue | — | — | May 25 | Aug 3 – Oct 5 | 70–90 |
| Sage | — | — | May 25 | Aug 10 – Oct 5 | 75–90 |
| Savory | — | — | May 25 | Jul 20 – Sep 14 | 50–70 |
| Sorrel | Apr 6 | May 11 | May 11 | Jun 22 – Aug 24 | 40–60 |
| Tarragon | — | — | May 25 | Jul 27 – Oct 5 | 60–90 |
| Thai Basil | Mar 23 | May 25 | Jun 8 | Aug 3 – Oct 5 | 50–75 |
| Thyme | — | — | May 25 | Aug 3 – Oct 5 | 70–90 |
| Valerian | — | — | May 25 | Sep 28 – Oct 19 | 120–180 |
| Yarrow | — | — | May 25 | Aug 24 – Oct 19 | 90–120 |
Monthly Planting Guide for Petroleum County
Gardening Guides & Resources
Helpful guides from The Ultimate Homestead to improve your garden in Petroleum County.
Frequently Asked Questions
What planting zone is Petroleum County, MT?
Petroleum County is in USDA Hardiness Zone 4b. This zone classification determines which perennial plants survive winter and sets the baseline for frost timing across the county.
When is the last frost in Petroleum County, MT?
Based on 31 years of NOAA weather station data, the median last spring frost in Petroleum County falls around May 18. In 8 out of 10 years, last frost lands between May 4 and May 30 — a 26-day window of variability. Use May 30 as your conservative safe-to-plant date for frost-sensitive crops.
When is the first fall frost in Petroleum County, MT?
The median first fall frost in Petroleum County arrives around September 24. In cold years it can arrive as early as September 11; in mild years as late as October 9. Harvest or protect frost-sensitive crops — tomatoes, peppers, basil, squash — before this date.
How long is the growing season in Petroleum County?
Petroleum County has a frost-free growing season of approximately 129 days. Focus on short-season varieties and start warm-season crops indoors 6–8 weeks before last frost. Climate records show the growing season is trending longer by about 2.73 days per decade.
What is the soil like in Petroleum County for gardening?
Petroleum County has predominantly Loam soil with a pH range of 6.8–8.2 and Excessively Drained drainage. Most vegetables and herbs grow well with standard composting and seasonal soil amendment.
What is grown commercially in Petroleum County?
Petroleum County has commercial agriculture that includes Hay, Cattle, Wheat. These crops reflect the local climate and soil conditions — what succeeds commercially often translates well to home gardens in the same area.
Is Petroleum County a good location for home gardening?
Petroleum County scores 28/100 (Challenging) on our Microclimate Index, which combines frost reliability, drought pressure, soil challenge, elevation risk, and long-term climate trend. Gardening here benefits from close attention to frost timing and season extension due to the challenging microclimate factors.
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.
The Gardener's Encyclopedia to Companion Planting
The pairings that make vegetables, herbs, and flowers grow better — and the ones that quietly wreck a bed.
- Proven pairings for 200+ vegetables, herbs, flowers, and fruits
- Full seed-starting + planting schedule with timing and spacing
- Bonus: square-foot gardening guide + printable seasonal planners
Seed Saving & Storage Guide
Most saved seeds go bad before next season. This shows exactly when to pick, how to dry, and where to store seeds from 200 plants so yours don't.
- 200 plants, step-by-step: life cycle, pollination type, isolation
- Exact temperature + humidity ranges that keep seeds viable
- Bonus: searchable Google Sheets tracker + custom GPT assistant
Composting Guide for Homesteaders
Turn kitchen scraps and yard waste into compost that actually feeds the garden — instead of a pile that smells, attracts pests, and never breaks down.
- 14 sections on composting methods, soil science, and troubleshooting
- The 7-step hot-compost system from start to finish
- Bonus tools: troubleshooting chart, safety guide, monitoring log