Washington County, MN — Planting Guide
Washington County is in USDA Zone 4a. The average last spring frost is April 23 and the first fall frost is October 9, giving you a growing season of approximately 169 days.
At an elevation of 832 ft, Washington County receives approximately 30.5 in of rainfall annually. Summer highs average 85°F with winter lows around 2°F. The predominant soil type is Silt Loam.
Based on 31 years of NOAA climate station data, the last frost date here varies by 34 days year to year — ranging from April 9 in warm years to May 13 in cold years. The growing season is trending shorter by about 1.51 days per decade. Washington County scores 67/100 (Good) on the Microclimate Index.
🌡️ Zone
4a (-30°F to -25°F min)
❄️ Last Frost
April 23
🍂 First Frost
October 9
📅 Growing Season
169 days
⛰️ Elevation
832 ft
🌧️ Annual Rainfall
30.5 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 | 1.6 in | 7 days | — | None |
| Mar | 2.4 in | 9 days | — | None |
| Apr | 3 in | 10 days | 1.3 in | Moderate |
| May | 3.4 in | 10 days | 0.9 in | Moderate |
| Jun | 4.1 in | 9 days | 0.2 in | Low |
| Jul | 3.1 in | 9 days | 1.2 in | Moderate |
| Aug | 3.3 in | 9 days | 1 in | Moderate |
| Sep | 2.4 in | 7 days | 1.9 in | High |
| Oct | 2.4 in | 8 days | 1.9 in | High |
| Nov | 2.2 in | 7 days | — | None |
| Dec | 1.5 in | 7 days | — | None |
Annual total: 30.5 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.
Washington County Soil Profile
Soil Type
Silt Loam
Soil pH
5.8-6.9
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 13 | Oct 26 | 166 days |
| Cautious | May 1 | Oct 16 | 168 days |
| Average year | Apr 23 | Oct 9 | 169 days |
| Optimistic | Apr 17 | Oct 4 | 170 days |
| Aggressive (risky) | Apr 9 | Sep 22 | 166 days |
Not very — frost dates can vary by ±34 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 shorter here (about 1.5 days per decade). Use the "Conservative" dates and choose fast-maturing varieties.
Gardening Difficulty Score
Washington County offers good growing conditions. A little planning around frost dates goes a long way.
Local Gardening Help in Washington 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 Washington County's climate and soil.
County Extension Office
Washington County University of Minnesota Extension Extension Office
Phone: 612-625-8173
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 Washington County
Finding local nurseries & garden centers in Washington County
Why Buy Local
Local nurseries carry plants that are proven to grow in your area. Staff can give you advice specific to Washington 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 Washington County MN" or "garden center Washington 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 Washington County MN" or check your extension office and local parks department. Facebook groups like "Washington County Gardeners" or "Minnesota 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
15.4 hours
Summer solstice daylight
Shortest Day
8.6 hours
Winter solstice daylight
Peak Sun Hours
9.9 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 | 8.9 hr | 3.4 hr | Short day |
| February | 10.2 hr | 4.4 hr | Short day |
| March | 11.6 hr | 5.8 hr | Short day |
| April | 13.3 hr | 7 hr | Neutral |
| May | 14.7 hr | 8.8 hr | Long day |
| June | 15.4 hr | 9.7 hr | Long day |
| July | 15.1 hr | 9.9 hr | Long day |
| August | 13.9 hr | 8.6 hr | Neutral |
| September | 12.3 hr | 7 hr | Neutral |
| October | 10.7 hr | 5.5 hr | Short day |
| November | 9.3 hr | 3.8 hr | Short day |
| December | 8.6 hr | 3.2 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 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 | 13°F | 23°F | ❄️ Dormant | ~36 weeks |
| Feb | 18°F | 23°F | ❄️ Dormant | ~36 weeks |
| Mar | 27°F | 29°F | ❄️ Dormant | ~36 weeks |
| Apr | 41°F | 39°F | 🐢 Slow | ~24 weeks |
| May | 54°F | 50°F | ♻️ Active | ~14 weeks |
| Jun | 66°F | 59°F | 🔥 Peak | ~8 weeks |
| Jul | 71°F | 66°F | 🔥 Peak | ~8 weeks |
| Aug | 74°F | 69°F | 🔥 Peak | ~8 weeks |
| Sep | 64°F | 63°F | ♻️ Active | ~14 weeks |
| Oct | 52°F | 56°F | ♻️ Active | ~14 weeks |
| Nov | 38°F | 43°F | ❄️ Dormant | ~36 weeks |
| Dec | 21°F | 30°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 Washington 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 | Moderate | Jun, Jul |
| Flea beetles | Moderate | May, Jun, Jul |
| Slugs | Moderate | 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 Washington 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 | Apr 25 | Jul 31 | — | Rapid growth, attracts pollinators, suppresses weeds |
| White clover | Mar 26 | Aug 14 | ✓ 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 | May 24 | Sep 25 | — | 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 20 | Apr 2 | — | Deep taproot breaks compaction, excellent for clay soils |
| Hairy vetch | Jul 26 | Apr 2 | ✓ Yes | Excellent nitrogen fixer, good for depleted soils |
| Oats | Sep 13 | Apr 9 | — | Quick biomass, winterkills in cold zones — no spring tillage needed |
| Winter rye | Jul 7 | Apr 2 | — | Suppresses weeds, prevents erosion, breaks up compacted soil |
| Winter wheat | Jul 18 | Apr 2 | — | 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: 11 mph Summer: 9 mph
Fall: 11 mph Winter: 13 mph
Prevailing wind: SW. Moderate wind — consider a temporary windbreak for young seedlings.
Windbreak Benefit
5.3/10
Moderately beneficial — a simple fence or trellis can protect delicate crops from wind stress.
Frost Pocket Risk
Low
Relatively flat terrain (230 ft range). Frost pocket risk is minimal — garden placement is flexible.
Rainwater Harvesting Potential
How much water you can collect, when to collect it, and what size system you need for your garden.
Annual Collection
15,201 gal
Per 1,000 sq ft of roof area (at 80% collection efficiency)
Recommended Setup
6 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
May, Jun, Jul, 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 30.5 inches of rain per year
- A 1,000 sq ft roof can collect roughly 15,201 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 Washington County
Soil Type
Silt Loam
Soil pH 5.8–6.9 · Well Drained drainage
Native soil is well-suited to most vegetables and herbs with regular compost additions.
Watering Needs
Drought stress: 3.5/10
Low-to-moderate drought stress. Plan to water 1–2 times per week during peak summer. (30.5 in. annual rainfall)
Season Tips
169-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.
Free Garden Planner
Plan your entire garden season — organize planting dates, track what you're growing, and know exactly when to start seeds, transplant, and harvest.
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 Washington County
96 vegetables that grow well in Zone 4a with planting dates for Washington County.
Show all 96 vegetables with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Harvest | Days to Maturity |
|---|---|---|---|---|---|
| Acorn Squash | Mar 12 | May 7 | May 14 | Aug 6 – Sep 10 | 80–100 |
| Amaranth | Feb 19 | May 7 | May 14 | Aug 13 – Oct 1 | 90–120 |
| Arugula | Mar 12 | Apr 16 | Apr 23 | May 28 – Jul 30 | 30–50 |
| Asparagus | — | — | May 7 | — | 730–1095 |
| Beets | — | Apr 16 | — | Jun 11 – Jul 9 | 50–70 |
| Belgian Endive | Mar 12 | Apr 16 | Apr 23 | Aug 13 – Sep 17 | 110–150 |
| Black Beans | — | May 7 | — | Aug 6 – Sep 24 | 90–120 |
| Bok Choy | Mar 12 | Apr 16 | Apr 23 | Jun 4 – Jul 9 | 40–60 |
| Broccoli | Mar 12 | Apr 16 | Apr 23 | Jun 25 – Aug 6 | 60–90 |
| Broccoli Rabe | Mar 12 | Apr 16 | Apr 23 | Jun 4 – Jul 9 | 40–60 |
| Brussels Sprouts | Mar 12 | Apr 16 | Apr 23 | Jul 23 – Sep 17 | 90–130 |
| Butternut Squash | Mar 12 | May 7 | May 14 | Aug 13 – Sep 17 | 85–110 |
| Cabbage | Mar 12 | Apr 16 | Apr 23 | Jun 25 – Aug 20 | 60–100 |
| Carrots | — | Apr 16 | — | Jun 18 – Jul 23 | 60–80 |
| Cauliflower | Mar 12 | Apr 16 | Apr 23 | Jun 18 – Aug 20 | 55–100 |
| Celeriac | Mar 12 | Apr 16 | Apr 23 | Aug 6 – Sep 10 | 100–120 |
| Celery | Mar 12 | Apr 16 | Apr 23 | Jul 16 – Sep 10 | 80–120 |
| Celtuce | Mar 12 | Apr 16 | Apr 23 | Jun 25 – Aug 6 | 60–90 |
| Chard | Mar 12 | Apr 16 | Apr 23 | Jun 18 – Aug 6 | 50–60 |
| Chickpeas | Mar 12 | Apr 16 | Apr 23 | Jul 16 – Aug 27 | 80–110 |
| Chicory | Mar 12 | Apr 16 | Apr 23 | Jun 25 – Aug 6 | 60–85 |
| Chinese Cabbage | Mar 12 | Apr 16 | Apr 23 | Jun 18 – Jul 16 | 50–70 |
| Christmas Lima Beans | Feb 19 | May 7 | May 14 | Aug 6 – Sep 10 | 80–100 |
| Collard Greens | Mar 12 | Apr 16 | Apr 23 | Jun 18 – Aug 20 | 55–75 |
| Corn | — | May 7 | — | Jul 9 – Sep 3 | 60–100 |
| Cress | Mar 12 | Apr 16 | Apr 23 | May 7 – May 28 | 14–21 |
| Crookneck Squash | Mar 12 | May 7 | May 14 | Jul 2 – Jul 30 | 45–60 |
| Crosne | — | Apr 16 | — | Sep 17 – Sep 10 | 150–200 |
| Cucumber | Mar 12 | May 7 | May 14 | Jul 9 – Sep 3 | 50–70 |
| Daikon | — | Apr 16 | — | Jun 11 – Jul 9 | 50–70 |
| Delicata Squash | Mar 12 | May 7 | May 14 | Aug 6 – Sep 10 | 80–100 |
| Edamame | — | May 7 | — | Jul 23 – Sep 3 | 75–100 |
| Endive | Mar 12 | Apr 16 | Apr 23 | Jun 11 – Jul 16 | 45–65 |
| Escarole | Mar 12 | Apr 16 | Apr 23 | Jun 18 – Jul 16 | 50–70 |
| Fava Beans | Mar 12 | Apr 16 | Apr 23 | Jul 9 – Aug 20 | 75–100 |
| Fennel | Feb 19 | May 7 | May 14 | Jul 16 – Aug 27 | 60–90 |
| Garlic | — | — | — | — | 90–240 |
| Green Beans | — | May 7 | — | Jul 2 – Aug 27 | 50–65 |
| Horseradish | — | — | May 7 | Sep 10 – Oct 1 | 120–180 |
| Hubbard Squash | Mar 12 | May 7 | May 14 | Aug 27 – Oct 1 | 100–120 |
| Kabocha | Mar 12 | May 7 | May 14 | Aug 13 – Sep 10 | 85–100 |
| Kai Lan | Mar 12 | Apr 16 | Apr 23 | Jun 11 – Jul 9 | 45–60 |
| Kale | Mar 12 | Apr 16 | Apr 23 | Jun 18 – Aug 13 | 50–70 |
| Kidney Beans | — | May 7 | — | Aug 6 – Sep 10 | 85–110 |
| Kohlrabi | Mar 12 | Apr 16 | Apr 23 | Jun 11 – Jul 16 | 45–65 |
| Komatsuna | Mar 12 | Apr 16 | Apr 23 | May 28 – Jul 2 | 35–50 |
| Leeks | Mar 12 | Apr 16 | Apr 23 | Jul 23 – Sep 17 | 90–150 |
| Lentils | Mar 12 | Apr 16 | Apr 23 | Jul 16 – Aug 27 | 80–110 |
| Lettuce | Mar 12 | Apr 16 | Apr 23 | May 28 – Aug 6 | 30–60 |
| Lima Beans | — | May 7 | — | Jul 9 – Aug 20 | 60–90 |
| Mache | Mar 12 | Apr 16 | Apr 23 | Jun 4 – Jul 9 | 40–60 |
| Melon | Mar 12 | May 7 | May 14 | Jul 23 – Sep 10 | 70–100 |
| Microgreens | Mar 12 | Apr 16 | Apr 23 | Apr 30 – May 28 | 7–21 |
| Mitsuba | Mar 12 | Apr 16 | Apr 16 | Jun 11 – Aug 6 | 50–70 |
| Mizuna | Mar 12 | Apr 16 | Apr 23 | May 28 – Jun 25 | 30–45 |
| Mustard Greens | Mar 12 | Apr 16 | Apr 23 | May 28 – Jul 30 | 30–50 |
| Napa Cabbage | Mar 12 | Apr 16 | Apr 23 | Jun 18 – Jul 23 | 55–75 |
| Onion | Mar 12 | Apr 16 | Apr 23 | Jul 23 – Sep 10 | 90–120 |
| Pac Choi | Mar 12 | Apr 16 | Apr 23 | Jun 4 – Jul 2 | 40–55 |
| Parsnip | — | Apr 16 | — | Jul 30 – Sep 10 | 100–130 |
| Patty Pan Squash | Mar 12 | May 7 | May 14 | Jul 2 – Jul 30 | 45–60 |
| Peas | Mar 12 | Apr 16 | Apr 23 | Jun 18 – Aug 13 | 55–70 |
| Peppers | Feb 5 | May 7 | May 14 | Jul 16 – Sep 24 | 60–90 |
| Pole Beans | Feb 19 | May 7 | May 14 | Jul 9 – Sep 3 | 55–70 |
| Potatoes | Feb 19 | May 7 | May 14 | Jul 23 – Oct 1 | 70–120 |
| Pumpkin | Mar 12 | May 7 | May 14 | Aug 13 – Oct 1 | 85–120 |
| Purslane | Mar 12 | Apr 16 | Apr 23 | Jun 4 – Jul 9 | 40–60 |
| Radicchio | Mar 12 | Apr 16 | Apr 23 | Jun 25 – Jul 30 | 60–80 |
| Radish | — | Apr 16 | — | May 14 – Jun 4 | 22–35 |
| Rhubarb | — | — | May 21 | — | 365–730 |
| Romanesco | Mar 12 | Apr 16 | Apr 23 | Jul 9 – Aug 20 | 75–100 |
| Rutabaga | — | Apr 16 | — | Jul 9 – Aug 13 | 80–100 |
| Salsify | — | Apr 16 | — | Jul 30 – Sep 10 | 100–130 |
| Savoy Cabbage | Mar 12 | Apr 16 | Apr 23 | Jul 2 – Aug 27 | 70–110 |
| Scallions | Mar 12 | Apr 16 | Apr 23 | Jun 18 – Jul 16 | 50–70 |
| Scarlet Runner Beans | Feb 19 | May 7 | May 14 | Jul 16 – Aug 20 | 60–80 |
| Shallot | Mar 12 | Apr 16 | Apr 23 | Jul 23 – Sep 10 | 90–120 |
| Shiso | Feb 26 | Apr 30 | May 14 | Jul 9 – Sep 3 | 50–70 |
| Snap Peas | Feb 19 | May 7 | May 14 | Jul 9 – Sep 3 | 55–70 |
| Snow Peas | Mar 12 | Apr 16 | Apr 23 | Jun 18 – Aug 13 | 50–65 |
| Soybeans | — | May 7 | — | Jul 30 – Sep 24 | 80–120 |
| Spaghetti Squash | Mar 12 | May 7 | May 14 | Aug 13 – Sep 10 | 85–100 |
| Spinach | Mar 12 | Apr 16 | Apr 23 | May 28 – Jul 30 | 35–50 |
| Squash (Summer) | Mar 12 | May 7 | May 14 | Jul 2 – Sep 3 | 45–65 |
| Squash (Winter) | Mar 12 | May 7 | May 14 | Aug 6 – Oct 1 | 80–120 |
| Sunchoke | — | — | May 7 | Aug 27 – Oct 1 | 110–150 |
| Sunflower | Feb 19 | May 7 | May 14 | Jul 23 – Sep 10 | 70–100 |
| Sweet Corn | — | May 7 | — | Jul 9 – Aug 20 | 60–90 |
| Tatsoi | Mar 12 | Apr 16 | Apr 23 | May 28 – Jul 2 | 35–50 |
| Tomatillo | Feb 19 | May 7 | May 14 | Jul 16 – Sep 24 | 60–85 |
| Tomatoes | Feb 19 | May 7 | May 14 | Jul 16 – Sep 24 | 60–85 |
| Turnip | — | Apr 16 | — | May 28 – Jul 2 | 40–60 |
| Watercress | Mar 12 | Apr 16 | Apr 23 | Jun 4 – Jul 9 | 40–60 |
| Watermelon | Mar 12 | May 7 | May 14 | Jul 23 – Sep 10 | 70–100 |
| Wax Beans | — | May 7 | — | Jul 2 – Aug 27 | 50–65 |
| Zucchini | Mar 12 | May 7 | May 14 | Jul 2 – Aug 27 | 45–60 |
🍓 Fruits to Grow in Washington County
22 fruits that grow well in Zone 4a with planting dates for Washington County.
Show all 22 fruits with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Harvest | Days to Maturity |
|---|---|---|---|---|---|
| Alpine Strawberries | — | — | May 21 | Aug 20 – Oct 15 | 90–180 |
| Aronia | — | — | May 21 | — | 730–1095 |
| Blueberries | — | — | May 21 | — | 730–1095 |
| Cantaloupe | — | — | May 21 | Jul 30 – Sep 3 | 70–90 |
| Cranberries | — | — | May 21 | — | 730–1095 |
| Currants | — | — | May 21 | — | 730–1095 |
| Elderberries | — | — | May 21 | — | 730–1095 |
| Goji Berries | — | — | May 21 | — | 730–1095 |
| Gooseberries | — | — | May 21 | — | 730–1095 |
| Grapes | — | — | May 21 | — | 730–1095 |
| Ground Cherry | — | — | May 21 | Jul 30 – Sep 24 | 65–80 |
| Hardy Kiwi | — | — | May 21 | — | 1095–1825 |
| Haskaps | — | — | May 21 | — | 730–1095 |
| Honeydew | — | — | May 21 | Aug 13 – Sep 24 | 80–110 |
| Jostaberry | — | — | May 21 | — | 730–1095 |
| Lingonberries | — | — | May 21 | — | 730–1095 |
| Medlar | — | — | May 21 | — | 1095–1825 |
| Mulberries | — | — | May 21 | — | 730–1825 |
| Persimmon | — | — | May 21 | — | 1095–2555 |
| Raspberries | — | — | May 21 | — | 365–730 |
| Serviceberries | — | — | May 21 | — | 730–1095 |
| Strawberries | — | — | May 21 | Aug 20 – Oct 15 | 90–365 |
🌿 Herbs to Grow in Washington County
32 herbs that grow well in Zone 4a with planting dates for Washington County.
Show all 32 herbs with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Harvest | Days to Maturity |
|---|---|---|---|---|---|
| Angelica | Mar 12 | Apr 16 | Apr 16 | — | 365–730 |
| Anise | Mar 12 | Apr 16 | Apr 16 | Jul 16 – Sep 10 | 90–120 |
| Basil | Feb 26 | Apr 30 | May 14 | Jul 9 – Sep 10 | 50–75 |
| Bee Balm | — | — | Apr 30 | Jul 30 – Sep 24 | 90–120 |
| Borage | Mar 12 | Apr 16 | Apr 16 | Jun 11 – Jul 30 | 50–60 |
| Caraway | Mar 12 | Apr 16 | Apr 16 | — | 365–450 |
| Catnip | — | — | Apr 30 | Jul 2 – Sep 3 | 60–80 |
| Chamomile | Mar 12 | Apr 16 | Apr 16 | Jun 18 – Aug 27 | 60–90 |
| Chervil | Mar 12 | Apr 16 | Apr 16 | May 28 – Jul 30 | 40–60 |
| Chives | — | — | Apr 30 | Jul 2 – Sep 10 | 60–90 |
| Cilantro | Mar 12 | Apr 16 | Apr 16 | May 28 – Jul 30 | 40–60 |
| Comfrey | — | — | Apr 30 | Jul 2 – Sep 10 | 60–90 |
| Dill | Mar 12 | Apr 16 | Apr 16 | May 28 – Jul 30 | 40–60 |
| Echinacea | — | — | Apr 30 | Sep 3 – Sep 24 | 120–180 |
| Fennel (herb) | Mar 12 | Apr 16 | Apr 16 | Jun 18 – Aug 27 | 60–90 |
| Garlic Chives | — | — | Apr 30 | Jul 2 – Sep 10 | 60–90 |
| Horehound | — | — | Apr 30 | Jul 16 – Sep 10 | 75–90 |
| Hyssop | — | — | Apr 30 | Jul 9 – Sep 10 | 70–90 |
| Lemon Balm | — | — | Apr 30 | Jul 2 – Aug 20 | 60–70 |
| Lovage | — | — | Apr 30 | Jul 9 – Sep 10 | 70–90 |
| Mint | — | — | Apr 30 | Jul 2 – Sep 10 | 60–90 |
| Oregano | — | — | Apr 30 | Jul 2 – Sep 10 | 60–90 |
| Parsley | Mar 12 | Apr 16 | Apr 16 | Jun 18 – Aug 20 | 60–80 |
| Rue | — | — | Apr 30 | Jul 9 – Sep 10 | 70–90 |
| Sage | — | — | Apr 30 | Jul 16 – Sep 10 | 75–90 |
| Savory | — | — | Apr 30 | Jun 25 – Aug 20 | 50–70 |
| Sorrel | Mar 12 | Apr 16 | Apr 16 | May 28 – Jul 30 | 40–60 |
| Tarragon | — | — | Apr 30 | Jul 2 – Sep 10 | 60–90 |
| Thai Basil | Feb 26 | Apr 30 | May 14 | Jul 9 – Sep 10 | 50–75 |
| Thyme | — | — | Apr 30 | Jul 9 – Sep 10 | 70–90 |
| Valerian | — | — | Apr 30 | Sep 3 – Sep 24 | 120–180 |
| Yarrow | — | — | Apr 30 | Jul 30 – Sep 24 | 90–120 |
Monthly Planting Guide for Washington County
Gardening Guides & Resources
Helpful guides from The Ultimate Homestead to improve your garden in Washington County.
Frequently Asked Questions
What planting zone is Washington County, MN?
Washington 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 Washington County, MN?
Based on 31 years of NOAA weather station data, the median last spring frost in Washington County falls around April 23. In 8 out of 10 years, last frost lands between April 9 and May 13 — a 34-day window of variability. Use May 13 as your conservative safe-to-plant date for frost-sensitive crops.
When is the first fall frost in Washington County, MN?
The median first fall frost in Washington County arrives around October 9. In cold years it can arrive as early as September 22; in mild years as late as October 26. Harvest or protect frost-sensitive crops — tomatoes, peppers, basil, squash — before this date.
How long is the growing season in Washington County?
Washington County has a frost-free growing season of approximately 169 days. This is enough time for most warm-season crops including tomatoes, peppers, and squash with proper timing. Climate records show the growing season is trending shorter by about 1.51 days per decade.
What is the soil like in Washington County for gardening?
Washington County has predominantly Silt Loam soil with a pH range of 5.8–6.9 and Well Drained drainage. Most vegetables and herbs grow well with standard composting and seasonal soil amendment.
What is grown commercially in Washington County?
Washington County has commercial agriculture that includes Corn, Soybeans, Hay. These crops reflect the local climate and soil conditions — what succeeds commercially often translates well to home gardens in the same area.
Is Washington County a good location for home gardening?
Washington County scores 67/100 (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.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Washington County gardeners in Zone 4a organize planting dates, track what's growing, and never miss a planting window.
Get Your Free Garden Planner →Free download. Plan your entire garden season in minutes.
