Mercer County, ND — Planting Guide
What to do in July
A quick July briefing for Mercer County, North Dakota gardeners — what's urgent, what's next, and what can wait.
-
Begin indoor sowing: basil, pole beans, and thai basil
Label every cell. You will absolutely forget which is which otherwise.
-
Start harvesting carrots, green beans, and kale
The more you pick, the more the plant produces. Letting fruit overripen tells the plant it's time to stop.
-
Sow carrots, kale, and lettuce for an autumn harvest
Fall crops get sweeter with a light frost. Don't be afraid of cool nights.
August prep starts now
- Starting indoors: peppers, begonias, and geraniums
- First harvests: basil, carrots, and cucumber
- Fall sowing: alliums, crocus, and daffodils
Mercer County is in USDA Zone 4a. The average last spring frost is May 16 and the first fall frost is September 24, giving you a growing season of approximately 131 days.
At an elevation of 1,118 ft, Mercer County receives approximately 23 in of rainfall annually. Summer highs average 83°F with winter lows around 8°F. The predominant soil type is Loam.
Based on 31 years of NOAA climate station data, the last frost date here varies by 29 days year to year — ranging from May 1 in warm years to May 30 in cold years. The growing season is trending longer by about 0.79 days per decade. Mercer County scores 61/100 (Good) on the Microclimate Index.
🌡️ Zone
4a (-30°F to -25°F min)
❄️ Last Frost
May 16
🍂 First Frost
September 24
📅 Growing Season
131 days
⛰️ Elevation
1,118 ft
🌧️ Annual Rainfall
23 in
Monthly Watering Calendar for Mercer County
When you'll need to water your garden — based on average monthly rainfall vs. the ~1 inch/week most gardens need.
What this means for you: A drip irrigation system pays for itself in 1-2 seasons in any climate. Mercer County's 23" annual rainfall determines whether you'll run it weekly (dry zones) or maybe just during summer dry spells (wet zones).
View detailed monthly data
| Month | Avg Rainfall | Rainy Days | Extra Water Needed | Watering Effort |
|---|---|---|---|---|
| Jan | 1.4 in | 7 days | — | None |
| Feb | 1.6 in | 5 days | — | None |
| Mar | 2 in | 7 days | — | None |
| Apr | 2.4 in | 7 days | 1.9 in | High |
| May | 2.7 in | 8 days | 1.6 in | High |
| Jun | 1.8 in | 4 days | 2.5 in | High |
| Jul | 1.9 in | 6 days | 2.4 in | High |
| Aug | 2.3 in | 7 days | 2 in | High |
| Sep | 1.8 in | 5 days | 2.5 in | High |
| Oct | 1.9 in | 6 days | 2.4 in | High |
| Nov | 1.8 in | 5 days | — | None |
| Dec | 1.2 in | 7 days | — | None |
Annual total: 22.8 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.
Mercer County Soil Profile
Soil Type
Loam
Soil pH
6.2-7.5
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 6 | 129 days |
| Cautious | May 21 | Oct 3 | 135 days |
| Average year | May 16 | Sep 24 | 131 days |
| Optimistic | May 11 | Sep 19 | 131 days |
| Aggressive (risky) | May 1 | Sep 11 | 133 days |
Not very — frost dates can vary by ±29 days year-to-year. Use the "Conservative" row in the table below, and keep row covers handy for surprise late frosts.
Slightly — seasons are trending a bit longer (0.8 days/decade). Historical frost dates are still reliable for planning.
Gardening Difficulty Score
Mercer County offers good growing conditions. A little planning around frost dates goes a long way.
Local Gardening Help in Mercer 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 Mercer County's climate and soil.
County Extension Office
Mercer County North Dakota State University Extension Extension Office
Phone: 701-231-8944
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 Mercer County
Finding local nurseries & garden centers in Mercer County
Why Buy Local
Local nurseries carry plants that are proven to grow in your area. Staff can give you advice specific to Mercer 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 Mercer County ND" or "garden center Mercer 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 Mercer County ND" or check your extension office and local parks department. Facebook groups like "Mercer County Gardeners" or "North Dakota 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 in Mercer County
Monthly daylight hours and peak sun — critical for onion varieties, photoperiod-sensitive plants, and solar garden planning.
The practical takeaway: A 14-hour day in June produces dramatically more photosynthesis than a 10-hour day in November. Mercer County's seasonal swing determines which crops can pack growth into spring vs. limp through fall.
Longest Day
15.7 hours
Summer solstice daylight
Shortest Day
8.3 hours
Winter solstice daylight
Peak Sun Hours
11.1 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 | 4.6 hr | Short day |
| February | 10 hr | 5.8 hr | Short day |
| March | 11.6 hr | 7.3 hr | Short day |
| April | 13.4 hr | 8.1 hr | Neutral |
| May | 14.9 hr | 9.2 hr | Long day |
| June | 15.7 hr | 10.4 hr | Long day |
| July | 15.4 hr | 11.1 hr | Long day |
| August | 14.1 hr | 9.8 hr | Long day |
| September | 12.3 hr | 8.3 hr | Neutral |
| October | 10.6 hr | 7.2 hr | Short day |
| November | 9.1 hr | 5.4 hr | Short day |
| December | 8.3 hr | 4.4 hr | Short day |
Peak sun hours factor in typical cloud cover — use these for solar panel and shade-planning calculations.
Soil Temperature & Composting in Mercer County
Monthly soil temps tell you when to plant warm-season crops, and when your compost pile is actively working.
Why it matters: Soil temperature predicts plant emergence better than calendar dates. Mercer County's spring soil warm-up curve tells you which weeks are safe for direct-sow beans, cucumbers, squash, and corn.
Plant Warm Crops When
Soil reaches 60°F+
Soil warm enough from Jun through Sep.
Best Month to Compost
Jun
Microbial activity peaks when soil is warm.
Active Composting
6 months
Solid season. Piles go dormant in winter.
View detailed monthly data
| Month | Soil 4" Deep | Soil 8" Deep | Compost Activity | Time to Finish |
|---|---|---|---|---|
| Jan | 12°F | 23°F | ❄️ Dormant | ~36 weeks |
| Feb | 18°F | 21°F | ❄️ Dormant | ~36 weeks |
| Mar | 25°F | 27°F | ❄️ Dormant | ~36 weeks |
| Apr | 40°F | 39°F | 🐢 Slow | ~24 weeks |
| May | 54°F | 51°F | ♻️ Active | ~14 weeks |
| Jun | 65°F | 57°F | 🔥 Peak | ~8 weeks |
| Jul | 71°F | 66°F | 🔥 Peak | ~8 weeks |
| Aug | 72°F | 69°F | 🔥 Peak | ~8 weeks |
| Sep | 64°F | 63°F | ♻️ Active | ~14 weeks |
| Oct | 51°F | 56°F | ♻️ Active | ~14 weeks |
| Nov | 38°F | 42°F | ❄️ Dormant | ~36 weeks |
| Dec | 20°F | 31°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 Mercer County
Computed from local climate patterns — warmer, humid conditions increase pest generations and fungal disease risk.
Why this matters: In Mercer County's climate, pest pressure shapes which crops are easy and which are heartbreak. Tomatoes are easy in dry mountain air, hard in humid coast — same plant, completely different gardening experience.
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 | Low | 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 Mercer County
Cover crops protect bare soil, fix nitrogen, suppress weeds, and improve soil structure — with planting dates calibrated for your area.
The practical takeaway: The "chop and drop" approach to cover crops: cut them down right before flowering, let them lay on the surface as mulch, plant your vegetables through the mulch. Less work, healthier soil.
Spring Cover Crops (2 options) — Build soil before the main growing season
| Crop | Plant By | Terminate | N-Fixing | Soil Benefit |
|---|---|---|---|---|
| Buckwheat | May 23 | Jul 16 | — | Rapid growth, attracts pollinators, suppresses weeds |
| White clover | Apr 15 | 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 2 | Sep 3 | — | 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 5 | Apr 25 | — | Deep taproot breaks compaction, excellent for clay soils |
| Hairy vetch | Jul 8 | Apr 25 | ✓ Yes | Excellent nitrogen fixer, good for depleted soils |
| Oats | Aug 14 | May 2 | — | Quick biomass, winterkills in cold zones — no spring tillage needed |
| Winter rye | Jun 22 | May 2 | — | Suppresses weeds, prevents erosion, breaks up compacted soil |
| Winter wheat | Jun 23 | Apr 25 | — | Erosion control, weed suppression, good biomass |
Wind & Microclimate in Mercer County
The practical takeaway: Wind is the silent water thief. Every breeze pulls moisture from leaves and soil. Mercer County's 12.1 mph average is one piece of the watering math: rainfall + irrigation must exceed evaporation + transpiration, and wind boosts both losses.
Wind dries soil, stresses plants, and affects frost patterns. Understanding your exposure helps with garden placement.
Seasonal Wind Speed
Spring: 15 mph Summer: 12 mph
Fall: 15 mph Winter: 14 mph
Prevailing wind: S. Windy area — plant a windbreak hedge on the S 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
Low
Relatively flat terrain (163 ft range). Frost pocket risk is minimal — garden placement is flexible.
Rainwater Harvesting in Mercer County
How much water you can collect, when to collect it, and what size system you need for your garden.
The practical takeaway: Captured rainwater is better for plants than tap water (no chlorine), works during water restrictions, and reduces stormwater runoff. Mercer County's 23" annual rainfall is a meaningful pool — most homes could capture 10,000+ gallons a year with a decent system.
Annual Collection
11,363 gal
Per 1,000 sq ft of roof area (at 80% collection efficiency)
Recommended Setup
7 rain barrels (55 gal each)
For a typical 500 sq ft garden. Serious collectors: consider a 1,750 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
Jan, Feb, 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 22.8 inches of rain per year
- A 1,000 sq ft roof can collect roughly 11,363 gallons annually
- Rainwater harvesting is fully legal in your state
- Stock up on stored water before your dry season (Jan, Feb, Dec)
- Use a first-flush diverter to keep roof debris out of your collection
Soil & Growing Conditions in Mercer County
Soil Type
Loam
Soil pH 6.2–7.5 · Well Drained drainage
Native soil is well-suited to most vegetables and herbs with regular compost additions.
Watering Needs
Drought stress: 7.5/10
High drought stress. Consistent irrigation is essential — consider drip systems, heavy mulch, and drought-tolerant varieties.
Season Tips
131-day frost-free season
Start warm-season crops indoors and focus on short-season varieties. Cold frames extend your season by 3–4 weeks in fall.
Your Free Printable Garden Planner
Plan every bed, every planting, every harvest — in one place. This 22-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 Mercer County
95 vegetables that grow well in Zone 4a with planting dates for Mercer County.
Show all 95 vegetables with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Fall Plant | Harvest | Days to Maturity |
|---|---|---|---|---|---|---|
| Acorn Squash | Apr 4 | May 30 | Jun 6 | — | Aug 29 – Oct 3 | 80–100 |
| Amaranth | Mar 14 | May 30 | Jun 6 | — | Sep 5 – Oct 24 | 90–120 |
| Arugula | Apr 4 | May 9 | May 16 | Jul 2 | Jun 20 – Aug 22 | 30–50 |
| Asparagus | — | — | May 30 | — | — | 730–1095 |
| Beets | — | May 9 | — | Jul 2 | Jul 4 – Aug 1 | 50–70 |
| Belgian Endive | Apr 4 | May 9 | May 16 | Jul 2 | Sep 5 – Oct 10 | 110–150 |
| Black Beans | — | May 30 | — | — | Aug 29 – Oct 17 | 90–120 |
| Bok Choy | Apr 4 | May 9 | May 16 | Jul 2 | Jun 27 – Aug 1 | 40–60 |
| Broccoli | Apr 4 | May 9 | May 16 | Jul 2 | Jul 18 – Aug 29 | 60–90 |
| Broccoli Rabe | Apr 4 | May 9 | May 16 | Jul 2 | Jun 27 – Aug 1 | 40–60 |
| Brussels Sprouts | Apr 4 | May 9 | May 16 | Jul 2 | Aug 15 – Oct 10 | 90–130 |
| Butternut Squash | Apr 4 | May 30 | Jun 6 | — | Sep 5 – Oct 10 | 85–110 |
| Cabbage | Apr 4 | May 9 | May 16 | Jul 2 | Jul 18 – Sep 12 | 60–100 |
| Carrots | — | May 9 | — | Jul 2 | Jul 11 – Aug 15 | 60–80 |
| Cauliflower | Apr 4 | May 9 | May 16 | Jul 2 | Jul 11 – Sep 12 | 55–100 |
| Celeriac | Apr 4 | May 9 | May 16 | Jul 2 | Aug 29 – Oct 3 | 100–120 |
| Celery | Apr 4 | May 9 | May 16 | Jul 2 | Aug 8 – Oct 3 | 80–120 |
| Celtuce | Apr 4 | May 9 | May 16 | Jul 2 | Jul 18 – Aug 29 | 60–90 |
| Chard | Apr 4 | May 9 | May 16 | Jul 2 | Jul 11 – Aug 29 | 50–60 |
| Chickpeas | Apr 4 | May 9 | May 16 | Jul 2 | Aug 8 – Sep 19 | 80–110 |
| Chicory | Apr 4 | May 9 | May 16 | Jul 2 | Jul 18 – Aug 29 | 60–85 |
| Chinese Cabbage | Apr 4 | May 9 | May 16 | Jul 2 | Jul 11 – Aug 8 | 50–70 |
| Christmas Lima Beans | Mar 14 | May 30 | Jun 6 | — | Aug 29 – Oct 3 | 80–100 |
| Collard Greens | Apr 4 | May 9 | May 16 | Jul 2 | Jul 11 – Sep 12 | 55–75 |
| Corn | — | May 30 | — | — | Aug 1 – Sep 26 | 60–100 |
| Cress | Apr 4 | May 9 | May 16 | Jul 2 | May 30 – Jun 20 | 14–21 |
| Crookneck Squash | Apr 4 | May 30 | Jun 6 | — | Jul 25 – Aug 22 | 45–60 |
| Crosne | — | May 9 | — | Jul 2 | Oct 10 – Oct 3 | 150–200 |
| Cucumber | Apr 4 | May 30 | Jun 6 | — | Aug 1 – Sep 26 | 50–70 |
| Daikon | — | May 9 | — | Jul 2 | Jul 4 – Aug 1 | 50–70 |
| Delicata Squash | Apr 4 | May 30 | Jun 6 | — | Aug 29 – Oct 3 | 80–100 |
| Edamame | — | May 30 | — | — | Aug 15 – Sep 26 | 75–100 |
| Endive | Apr 4 | May 9 | May 16 | Jul 2 | Jul 4 – Aug 8 | 45–65 |
| Escarole | Apr 4 | May 9 | May 16 | Jul 2 | Jul 11 – Aug 8 | 50–70 |
| Fava Beans | Apr 4 | May 9 | May 16 | Jul 2 | Aug 1 – Sep 12 | 75–100 |
| Fennel | Mar 14 | May 30 | Jun 6 | — | Aug 8 – Sep 19 | 60–90 |
| Garlic | — | — | — | Aug 13 | Nov 12 – Jan 7 | 90–240 |
| Green Beans | — | May 30 | — | — | Jul 25 – Sep 19 | 50–65 |
| Horseradish | — | — | May 30 | — | Oct 3 – Oct 24 | 120–180 |
| Hubbard Squash | Apr 4 | May 30 | Jun 6 | — | Sep 19 – Oct 24 | 100–120 |
| Kabocha | Apr 4 | May 30 | Jun 6 | — | Sep 5 – Oct 3 | 85–100 |
| Kai Lan | Apr 4 | May 9 | May 16 | Jul 2 | Jul 4 – Aug 1 | 45–60 |
| Kale | Apr 4 | May 9 | May 16 | Jul 2 | Jul 11 – Sep 5 | 50–70 |
| Kidney Beans | — | May 30 | — | — | Aug 29 – Oct 3 | 85–110 |
| Kohlrabi | Apr 4 | May 9 | May 16 | Jul 2 | Jul 4 – Aug 8 | 45–65 |
| Komatsuna | Apr 4 | May 9 | May 16 | Jul 2 | Jun 20 – Jul 25 | 35–50 |
| Leeks | Apr 4 | May 9 | May 16 | Jul 2 | Aug 15 – Oct 10 | 90–150 |
| Lentils | Apr 4 | May 9 | May 16 | Jul 2 | Aug 8 – Sep 19 | 80–110 |
| Lettuce | Apr 4 | May 9 | May 16 | Jul 2 | Jun 20 – Aug 29 | 30–60 |
| Lima Beans | — | May 30 | — | — | Aug 1 – Sep 12 | 60–90 |
| Mache | Apr 4 | May 9 | May 16 | Jul 2 | Jun 27 – Aug 1 | 40–60 |
| Melon | Apr 4 | May 30 | Jun 6 | — | Aug 15 – Oct 3 | 70–100 |
| Microgreens | Apr 4 | May 9 | May 16 | Jul 2 | May 23 – Jun 20 | 7–21 |
| Mitsuba | Apr 4 | May 9 | May 9 | Jul 2 | Jul 4 – Aug 29 | 50–70 |
| Mizuna | Apr 4 | May 9 | May 16 | Jul 2 | Jun 20 – Jul 18 | 30–45 |
| Mustard Greens | Apr 4 | May 9 | May 16 | Jul 2 | Jun 20 – Aug 22 | 30–50 |
| Napa Cabbage | Apr 4 | May 9 | May 16 | Jul 2 | Jul 11 – Aug 15 | 55–75 |
| Onion | Apr 4 | May 9 | May 16 | Jul 2 | Aug 15 – Oct 3 | 90–120 |
| Pac Choi | Apr 4 | May 9 | May 16 | Jul 2 | Jun 27 – Jul 25 | 40–55 |
| Parsnip | — | May 9 | — | Jul 2 | Aug 22 – Oct 3 | 100–130 |
| Patty Pan Squash | Apr 4 | May 30 | Jun 6 | — | Jul 25 – Aug 22 | 45–60 |
| Peas | Apr 4 | May 9 | May 16 | Jul 2 | Jul 11 – Sep 5 | 55–70 |
| Peppers | Feb 28 | May 30 | Jun 6 | — | Aug 8 – Oct 17 | 60–90 |
| Pole Beans | Mar 14 | May 30 | Jun 6 | — | Aug 1 – Sep 26 | 55–70 |
| Potatoes | Mar 14 | May 30 | Jun 6 | — | Aug 15 – Oct 24 | 70–120 |
| Pumpkin | Apr 4 | May 30 | Jun 6 | — | Sep 5 – Oct 24 | 85–120 |
| Purslane | Apr 4 | May 9 | May 16 | Jul 2 | Jun 27 – Aug 1 | 40–60 |
| Radicchio | Apr 4 | May 9 | May 16 | Jul 2 | Jul 18 – Aug 22 | 60–80 |
| Radish | — | May 9 | — | Jul 2 | Jun 6 – Jun 27 | 22–35 |
| Rhubarb | — | — | Jun 13 | — | — | 365–730 |
| Romanesco | Apr 4 | May 9 | May 16 | Jul 2 | Aug 1 – Sep 12 | 75–100 |
| Rutabaga | — | May 9 | — | Jul 2 | Aug 1 – Sep 5 | 80–100 |
| Salsify | — | May 9 | — | Jul 2 | Aug 22 – Oct 3 | 100–130 |
| Savoy Cabbage | Apr 4 | May 9 | May 16 | Jul 2 | Jul 25 – Sep 19 | 70–110 |
| Scallions | Apr 4 | May 9 | May 16 | Jul 2 | Jul 11 – Aug 8 | 50–70 |
| Scarlet Runner Beans | Mar 14 | May 30 | Jun 6 | — | Aug 8 – Sep 12 | 60–80 |
| Shallot | Apr 4 | May 9 | May 16 | Jul 2 | Aug 15 – Oct 3 | 90–120 |
| Shiso | Mar 21 | May 23 | Jun 6 | — | Aug 1 – Sep 26 | 50–70 |
| Snap Peas | Mar 14 | May 30 | Jun 6 | — | Aug 1 – Sep 26 | 55–70 |
| Snow Peas | Apr 4 | May 9 | May 16 | Jul 2 | Jul 11 – Sep 5 | 50–65 |
| Soybeans | — | May 30 | — | — | Aug 22 – Oct 17 | 80–120 |
| Spaghetti Squash | Apr 4 | May 30 | Jun 6 | — | Sep 5 – Oct 3 | 85–100 |
| Spinach | Apr 4 | May 9 | May 16 | Jul 2 | Jun 20 – Aug 22 | 35–50 |
| Squash (Summer) | Apr 4 | May 30 | Jun 6 | — | Jul 25 – Sep 26 | 45–65 |
| Squash (Winter) | Apr 4 | May 30 | Jun 6 | — | Aug 29 – Oct 24 | 80–120 |
| Sunchoke | — | — | May 30 | — | Sep 19 – Oct 24 | 110–150 |
| Sweet Corn | — | May 30 | — | — | Aug 1 – Sep 12 | 60–90 |
| Tatsoi | Apr 4 | May 9 | May 16 | Jul 2 | Jun 20 – Jul 25 | 35–50 |
| Tomatillo | Mar 14 | May 30 | Jun 6 | — | Aug 8 – Oct 17 | 60–85 |
| Tomatoes | Mar 14 | May 30 | Jun 6 | — | Aug 8 – Oct 17 | 60–85 |
| Turnip | — | May 9 | — | Jul 2 | Jun 20 – Jul 25 | 40–60 |
| Watercress | Apr 4 | May 9 | May 16 | Jul 2 | Jun 27 – Aug 1 | 40–60 |
| Watermelon | Apr 4 | May 30 | Jun 6 | — | Aug 15 – Oct 3 | 70–100 |
| Wax Beans | — | May 30 | — | — | Jul 25 – Sep 19 | 50–65 |
| Zucchini | Apr 4 | May 30 | Jun 6 | — | Jul 25 – Sep 19 | 45–60 |
🍓 Fruits to Grow in Mercer County
22 fruits that grow well in Zone 4a with planting dates for Mercer County.
Show all 22 fruits with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Fall Plant | Harvest | Days to Maturity |
|---|---|---|---|---|---|---|
| Alpine Strawberries | — | — | Jun 13 | — | Sep 12 – Nov 7 | 90–180 |
| Aronia | — | — | Jun 13 | — | — | 730–1095 |
| Blueberries | — | — | Jun 13 | — | — | 730–1095 |
| Cantaloupe | — | — | Jun 13 | — | Aug 22 – Sep 26 | 70–90 |
| Cranberries | — | — | Jun 13 | — | — | 730–1095 |
| Currants | — | — | Jun 13 | — | — | 730–1095 |
| Elderberries | — | — | Jun 13 | — | — | 730–1095 |
| Goji Berries | — | — | Jun 13 | — | — | 730–1095 |
| Gooseberries | — | — | Jun 13 | — | — | 730–1095 |
| Grapes | — | — | Jun 13 | — | — | 730–1095 |
| Ground Cherry | — | — | Jun 13 | — | Aug 22 – Oct 17 | 65–80 |
| Hardy Kiwi | — | — | Jun 13 | — | — | 1095–1825 |
| Haskaps | — | — | Jun 13 | — | — | 730–1095 |
| Honeydew | — | — | Jun 13 | — | Sep 5 – Oct 17 | 80–110 |
| Jostaberry | — | — | Jun 13 | — | — | 730–1095 |
| Lingonberries | — | — | Jun 13 | — | — | 730–1095 |
| Medlar | — | — | Jun 13 | — | — | 1095–1825 |
| Mulberries | — | — | Jun 13 | — | — | 730–1825 |
| Persimmon | — | — | Jun 13 | — | — | 1095–2555 |
| Raspberries | — | — | Jun 13 | — | — | 365–730 |
| Serviceberries | — | — | Jun 13 | — | — | 730–1095 |
| Strawberries | — | — | Jun 13 | — | Sep 12 – Nov 7 | 90–365 |
🌿 Herbs to Grow in Mercer County
30 herbs that grow well in Zone 4a with planting dates for Mercer County.
Show all 30 herbs with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Fall Plant | Harvest | Days to Maturity |
|---|---|---|---|---|---|---|
| Angelica | Apr 4 | May 9 | May 9 | Jul 2 | — | 365–730 |
| Anise | Apr 4 | May 9 | May 9 | Jul 2 | Aug 8 – Oct 3 | 90–120 |
| Basil | Mar 21 | May 23 | Jun 6 | — | Aug 1 – Oct 3 | 50–75 |
| Bee Balm | — | — | May 23 | — | Aug 22 – Oct 17 | 90–120 |
| Borage | Apr 4 | May 9 | May 9 | Jul 2 | Jul 4 – Aug 22 | 50–60 |
| Caraway | Apr 4 | May 9 | May 9 | Jul 2 | — | 365–450 |
| Catnip | — | — | May 23 | — | Jul 25 – Sep 26 | 60–80 |
| Chamomile | Apr 4 | May 9 | May 9 | Jul 2 | Jul 11 – Sep 19 | 60–90 |
| Chervil | Apr 4 | May 9 | May 9 | Jul 2 | Jun 20 – Aug 22 | 40–60 |
| Chives | — | — | May 23 | — | Jul 25 – Oct 3 | 60–90 |
| Cilantro | Apr 4 | May 9 | May 9 | Jul 2 | Jun 20 – Aug 22 | 40–60 |
| Comfrey | — | — | May 23 | — | Jul 25 – Oct 3 | 60–90 |
| Dill | Apr 4 | May 9 | May 9 | Jul 2 | Jun 20 – Aug 22 | 40–60 |
| Fennel (herb) | Apr 4 | May 9 | May 9 | Jul 2 | Jul 11 – Sep 19 | 60–90 |
| Garlic Chives | — | — | May 23 | — | Jul 25 – Oct 3 | 60–90 |
| Horehound | — | — | May 23 | — | Aug 8 – Oct 3 | 75–90 |
| Hyssop | — | — | May 23 | — | Aug 1 – Oct 3 | 70–90 |
| Lemon Balm | — | — | May 23 | — | Jul 25 – Sep 12 | 60–70 |
| Lovage | — | — | May 23 | — | Aug 1 – Oct 3 | 70–90 |
| Mint | — | — | May 23 | — | Jul 25 – Oct 3 | 60–90 |
| Oregano | — | — | May 23 | — | Jul 25 – Oct 3 | 60–90 |
| Parsley | Apr 4 | May 9 | May 9 | Jul 2 | Jul 11 – Sep 12 | 60–80 |
| Rue | — | — | May 23 | — | Aug 1 – Oct 3 | 70–90 |
| Sage | — | — | May 23 | — | Aug 8 – Oct 3 | 75–90 |
| Savory | — | — | May 23 | — | Jul 18 – Sep 12 | 50–70 |
| Sorrel | Apr 4 | May 9 | May 9 | Jul 2 | Jun 20 – Aug 22 | 40–60 |
| Tarragon | — | — | May 23 | — | Jul 25 – Oct 3 | 60–90 |
| Thai Basil | Mar 21 | May 23 | Jun 6 | — | Aug 1 – Oct 3 | 50–75 |
| Thyme | — | — | May 23 | — | Aug 1 – Oct 3 | 70–90 |
| Valerian | — | — | May 23 | — | Sep 26 – Oct 17 | 120–180 |
🌸 Flowers to Grow in Mercer County
49 flowers that grow well in Zone 4a with planting dates for Mercer County.
Show all 49 flowers with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Fall Plant | Bloom | Days to Maturity |
|---|---|---|---|---|---|---|
| Ageratum | Mar 21 | May 23 | May 23 | — | Jul 18 – Sep 26 | 60–75 |
| Alliums | — | — | — | Aug 13 | Sep 24 – Oct 15 | 28–42 |
| Astilbe | Mar 7 | — | May 30 | — | Aug 22 – Oct 17 | 70–100 |
| Bachelor's Button | Mar 28 | May 2 | May 16 | — | Jul 18 – Sep 19 | 60–90 |
| Begonias | Feb 28 | — | May 30 | — | Aug 8 – Oct 10 | 70–90 |
| Black-eyed Susan | Mar 7 | May 16 | May 30 | — | Aug 22 – Oct 31 | 60–80 |
| Bleeding Hearts | Mar 7 | — | May 30 | — | Jul 25 – Sep 5 | 60–90 |
| Calendula | Mar 28 | May 2 | May 16 | — | Jul 4 – Sep 19 | 50–70 |
| Celosia | Apr 4 | May 30 | May 30 | — | Aug 1 – Oct 17 | 60–90 |
| Columbine | Mar 7 | May 30 | May 30 | — | Jul 25 – Sep 5 | 70–100 |
| Coreopsis | Mar 7 | May 23 | May 30 | — | Aug 15 – Oct 31 | 60–80 |
| Cosmos | Apr 18 | May 23 | May 23 | — | Aug 1 – Oct 17 | 60–90 |
| Crocus | — | — | — | Aug 13 | Jun 18 – Jul 9 | 10–20 |
| Daffodils | — | — | — | Aug 13 | Jun 25 – Jul 16 | 20–40 |
| Dahlias | Apr 18 | May 30 | May 30 | — | Aug 29 – Oct 31 | 70–120 |
| Daylily | Mar 7 | — | May 30 | — | Aug 29 – Oct 31 | 60–90 |
| Dianthus | Mar 14 | Apr 25 | May 9 | — | Jun 27 – Aug 29 | 60–80 |
| Echinacea (Purple Coneflower) | Mar 7 | May 30 | May 30 | — | Aug 29 – Oct 31 | 70–90 |
| Foxglove | Mar 7 | May 30 | May 30 | — | Jul 25 – Sep 5 | 80–120 |
| Gaillardia (Blanket Flower) | Mar 21 | May 30 | May 30 | — | Aug 8 – Nov 7 | 70–100 |
| Geraniums | Feb 28 | — | May 30 | — | Aug 8 – Oct 10 | 70–100 |
| Gladiolus | — | May 23 | May 23 | — | Aug 22 – Oct 24 | 70–100 |
| Hostas | Feb 28 | — | May 30 | — | Aug 29 – Oct 31 | 60–90 |
| Hyacinths | — | — | — | Aug 13 | Jul 16 – Aug 6 | 14–28 |
| Hydrangeas | Feb 28 | — | May 30 | — | Aug 22 – Oct 17 | 90–150 |
| Impatiens | Mar 14 | — | May 30 | — | Aug 15 – Oct 10 | 60–75 |
| Irises | — | Division | May 30 | — | Jul 25 – Aug 22 | 60–100 |
| Larkspur | — | Apr 11 | — | — | Jun 20 – Aug 1 | 60–90 |
| Lilies | — | Division | May 30 | — | Aug 22 – Oct 24 | 70–120 |
| Lobelia | Mar 7 | — | May 16 | — | Jul 11 – Sep 5 | 70–80 |
| Lupine | Mar 7 | May 30 | May 30 | — | Jul 25 – Sep 5 | 75–100 |
| Marigolds | Apr 4 | May 30 | May 30 | — | Jul 25 – Oct 10 | 50–70 |
| Nasturtium | Apr 18 | May 30 | May 30 | — | Jul 25 – Oct 10 | 55–65 |
| Pansy | Feb 28 | — | May 16 | — | Jul 11 – Aug 29 | 70–90 |
| Peonies | — | Division | May 30 | — | Aug 8 – Sep 12 | 90–120 |
| Petunia | Mar 14 | — | May 30 | — | Aug 15 – Oct 17 | 70–90 |
| Phlox | Mar 7 | May 30 | May 30 | — | Aug 22 – Oct 24 | 80–110 |
| Portulaca | Apr 4 | May 30 | May 30 | — | Jul 18 – Sep 26 | 50–70 |
| Roses | Feb 28 | — | May 30 | — | Aug 22 – Oct 31 | 90–180 |
| Salvia | Mar 7 | — | May 30 | — | Aug 8 – Oct 10 | 70–90 |
| Sedum (Stonecrop) | Mar 7 | — | May 30 | — | Oct 3 – Nov 21 | 60–90 |
| Snapdragon | Feb 28 | — | May 16 | — | Jul 25 – Sep 19 | 70–100 |
| Sunflower | Apr 25 | May 30 | May 30 | — | Aug 22 – Oct 17 | 70–100 |
| Sweet Alyssum | Mar 21 | May 9 | May 16 | — | Jun 27 – Aug 29 | 45–60 |
| Sweet Pea | Mar 28 | Apr 11 | May 16 | — | Aug 8 – Sep 19 | 65–85 |
| Tulips | — | — | — | Aug 13 | Jul 9 – Jul 30 | 15–30 |
| Vinca (Annual) | Feb 28 | — | May 30 | — | Aug 8 – Oct 10 | 70–90 |
| Yarrow | Mar 7 | May 16 | May 30 | — | Aug 15 – Oct 31 | 60–90 |
| Zinnia | Apr 18 | May 30 | May 30 | — | Aug 8 – Oct 17 | 60–70 |
Monthly Planting Guide for Mercer County
Gardening Guides & Resources
Helpful guides from The Ultimate Homestead to improve your garden in Mercer County.
Frequently Asked Questions
What planting zone is Mercer County, ND?
Mercer County is in USDA Hardiness Zone 4a. 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 Mercer County, ND?
Based on 31 years of NOAA weather station data, the median last spring frost in Mercer County falls around May 16. In 8 out of 10 years, last frost lands between May 1 and May 30 — a 29-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 Mercer County, ND?
The median first fall frost in Mercer County arrives around September 24. In cold years it can arrive as early as September 11; in mild years as late as October 6. Harvest or protect frost-sensitive crops — tomatoes, peppers, basil, squash — before this date.
How long is the growing season in Mercer County?
Mercer County has a frost-free growing season of approximately 131 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 0.79 days per decade.
What is the soil like in Mercer County for gardening?
Mercer County has predominantly Loam soil with a pH range of 6.2–7.5 and Well Drained drainage. Most vegetables and herbs grow well with standard composting and seasonal soil amendment.
What is grown commercially in Mercer County?
Mercer County has commercial agriculture that includes Wheat, Soybeans, Corn. These crops reflect the local climate and soil conditions — what succeeds commercially often translates well to home gardens in the same area.
Is Mercer County a good location for home gardening?
Mercer County scores 61/100 (Good) on our Microclimate Index, which combines frost reliability, drought pressure, soil challenge, elevation risk, and long-term climate trend. Conditions here are moderate — most common crops grow well with standard timing and care.
Your Mercer County Garden Planner — Free
A 22-page printable planner built for Mercer 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.
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