Washington County, ID — Planting Guide
Washington County is in USDA Zone 6a. The average last spring frost is May 9 and the first fall frost is October 1, giving you a growing season of approximately 145 days.
At an elevation of 4,048 ft, Washington County receives approximately 17.9 in of rainfall annually. Summer highs average 85°F with winter lows around 27°F. The predominant soil type is Loam.
Based on 30 years of NOAA climate station data, the last frost date here varies by 52 days year to year — ranging from April 16 in warm years to June 7 in cold years. The growing season is trending longer by about 8.53 days per decade. Washington County scores 38/100 (Challenging) on the Microclimate Index.
🌡️ Zone
6a (-10°F to -5°F min)
❄️ Last Frost
May 9
🍂 First Frost
October 1
📅 Growing Season
145 days
⛰️ Elevation
4,048 ft
🌧️ Annual Rainfall
17.9 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 | 6 days | — | None |
| Feb | 1.2 in | 5 days | — | None |
| Mar | 1.9 in | 7 days | 2.4 in | High |
| Apr | 1.7 in | 8 days | 2.6 in | High |
| May | 2 in | 7 days | 2.3 in | High |
| Jun | 1.2 in | 4 days | 3.1 in | Critical |
| Jul | 1.6 in | 5 days | 2.7 in | High |
| Aug | 1.7 in | 7 days | 2.6 in | High |
| Sep | 1.5 in | 5 days | 2.8 in | High |
| Oct | 1.5 in | 6 days | 2.8 in | High |
| Nov | 1.4 in | 6 days | — | None |
| Dec | 1 in | 7 days | — | None |
Annual total: 17.8 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.
Washington County Soil Profile
Soil Type
Loam
Soil pH
6.2-7.8
Drainage
Well Drained
Frost Risk Probability
Based on 30 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) | Jun 7 | Oct 21 | 136 days |
| Cautious | May 19 | Oct 9 | 143 days |
| Average year | May 9 | Oct 1 | 145 days |
| Optimistic | May 1 | Sep 24 | 146 days |
| Aggressive (risky) | Apr 16 | Sep 12 | 149 days |
Not very — frost dates can vary by ±52 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 8.5 days per decade). Spring is arriving earlier than it used to. Good news for gardeners.
Gardening Difficulty Score
Washington County has challenging growing conditions. Season extension and careful variety selection are essential.
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 Idaho Extension Extension Office
Phone: 208-885-6681
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 ID" 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 ID" or check your extension office and local parks department. Facebook groups like "Washington County Gardeners" or "Idaho 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
15.3 hours
Summer solstice daylight
Shortest Day
8.7 hours
Winter solstice daylight
Peak Sun Hours
10.8 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 | 9 hr | 4.7 hr | Short day |
| February | 10.2 hr | 5.8 hr | Short day |
| March | 11.6 hr | 7.2 hr | Short day |
| April | 13.2 hr | 7.6 hr | Neutral |
| May | 14.6 hr | 9.5 hr | Long day |
| June | 15.3 hr | 10.8 hr | Long day |
| July | 15 hr | 10.1 hr | Long day |
| August | 13.9 hr | 9.6 hr | Neutral |
| September | 12.3 hr | 8.4 hr | Neutral |
| October | 10.7 hr | 6.8 hr | Short day |
| November | 9.3 hr | 5.2 hr | Short day |
| December | 8.7 hr | 4.7 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
Jul
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 | 18°F | 27°F | ❄️ Dormant | ~36 weeks |
| Feb | 22°F | 26°F | ❄️ Dormant | ~36 weeks |
| Mar | 30°F | 30°F | ❄️ Dormant | ~36 weeks |
| Apr | 38°F | 40°F | ❄️ Dormant | ~36 weeks |
| May | 51°F | 48°F | ♻️ Active | ~14 weeks |
| Jun | 61°F | 57°F | ♻️ Active | ~14 weeks |
| Jul | 69°F | 64°F | 🔥 Peak | ~8 weeks |
| Aug | 69°F | 67°F | 🔥 Peak | ~8 weeks |
| Sep | 64°F | 63°F | ♻️ Active | ~14 weeks |
| Oct | 51°F | 55°F | ♻️ Active | ~14 weeks |
| Nov | 39°F | 45°F | ❄️ Dormant | ~36 weeks |
| Dec | 25°F | 34°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 6 common pests in your area
| Pest | Risk Level | Peak Months |
|---|---|---|
| Aphids | High | Apr, May, Jun, Jul, Aug, Sep |
| Japanese beetles | Moderate | Jun, Jul, Aug |
| Squash vine borers | Moderate | Jun, Jul |
| Tomato hornworms | Moderate | Jun, Jul, Aug |
| Cucumber beetles | Low | May, Jun, Jul |
| Stink bugs | Moderate | 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 (3 options) — Build soil before the main growing season
| Crop | Plant By | Terminate | N-Fixing | Soil Benefit |
|---|---|---|---|---|
| Buckwheat | May 20 | Jul 23 | — | Rapid growth, attracts pollinators, suppresses weeds |
| Sorghum-sudan grass | May 12 | Jul 23 | — | Massive biomass, breaks compaction, suppresses nematodes |
| White clover | Apr 11 | Jul 30 | ✓ 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 8 | Sep 17 | — | Deep roots break compaction, attract pollinators and beneficial insects |
Fall Cover Crops (7 options) — Plant after harvest to protect soil over winter
| Crop | Plant By | Terminate | N-Fixing | Soil Benefit |
|---|---|---|---|---|
| Austrian winter peas | Aug 5 | Apr 18 | ✓ Yes | Fixes nitrogen, good for heavy clay soils |
| Crimson clover | Jul 27 | Apr 18 | ✓ Yes | Fixes nitrogen, attracts pollinators in spring |
| Daikon radish | Aug 5 | Apr 18 | — | Deep taproot breaks compaction, excellent for clay soils |
| Hairy vetch | Jul 22 | Apr 25 | ✓ Yes | Excellent nitrogen fixer, good for depleted soils |
| Oats | Sep 2 | Apr 18 | — | Quick biomass, winterkills in cold zones — no spring tillage needed |
| Winter rye | Jul 11 | Apr 18 | — | Suppresses weeds, prevents erosion, breaks up compacted soil |
| Winter wheat | Jul 11 | Apr 18 | — | 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: 14 mph Summer: 11 mph
Fall: 13 mph Winter: 15 mph
Prevailing wind: W. Windy area — plant a windbreak hedge on the W side of your garden.
Windbreak Benefit
7.5/10
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 1,362 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
8,871 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 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, 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 17.8 inches of rain per year
- A 1,000 sq ft roof can collect roughly 8,871 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 Washington County
Soil Type
Loam
Soil pH 6.2–7.8 · Excessively Drained drainage
Good candidate for raised beds to maximise drainage and extend the season.
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
145-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
108 vegetables that grow well in Zone 6a with planting dates for Washington County.
Show all 108 vegetables with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Harvest | Days to Maturity |
|---|---|---|---|---|---|
| Acorn Squash | Apr 4 | May 16 | May 23 | Aug 15 – Sep 19 | 80–100 |
| Amaranth | Mar 14 | May 16 | May 23 | Aug 22 – Oct 10 | 90–120 |
| Arugula | Apr 4 | Apr 25 | May 9 | Jun 13 – Aug 15 | 30–50 |
| Asparagus | — | — | May 23 | — | 730–1095 |
| Beets | — | Apr 25 | — | Jun 20 – Jul 18 | 50–70 |
| Belgian Endive | Apr 4 | Apr 25 | May 9 | Aug 29 – Oct 24 | 110–150 |
| Bitter Melon | Mar 14 | May 16 | May 23 | Jul 25 – Sep 5 | 60–90 |
| Black Beans | — | May 16 | — | Aug 15 – Oct 3 | 90–120 |
| Bok Choy | Apr 4 | Apr 25 | May 9 | Jun 20 – Jul 25 | 40–60 |
| Broccoli | Apr 4 | Apr 25 | May 9 | Jul 11 – Aug 22 | 60–90 |
| Broccoli Rabe | Apr 4 | Apr 25 | May 9 | Jun 20 – Jul 25 | 40–60 |
| Brussels Sprouts | Apr 4 | Apr 25 | May 9 | Aug 8 – Oct 3 | 90–130 |
| Butternut Squash | Apr 4 | May 16 | May 23 | Aug 22 – Sep 26 | 85–110 |
| Cabbage | Apr 4 | Apr 25 | May 9 | Jul 11 – Sep 5 | 60–100 |
| Calabash | Mar 14 | May 16 | May 23 | Aug 15 – Oct 10 | 80–120 |
| Carrots | — | Apr 25 | — | Jun 27 – Aug 1 | 60–80 |
| Cauliflower | Apr 4 | Apr 25 | May 9 | Jul 4 – Sep 5 | 55–100 |
| Celeriac | Apr 4 | Apr 25 | May 9 | Aug 22 – Sep 26 | 100–120 |
| Celery | Apr 4 | Apr 25 | May 9 | Aug 1 – Sep 26 | 80–120 |
| Celtuce | Apr 4 | Apr 25 | May 9 | Jul 11 – Aug 22 | 60–90 |
| Chard | Apr 4 | Apr 25 | May 9 | Jul 4 – Aug 22 | 50–60 |
| Chickpeas | Apr 4 | Apr 25 | May 9 | Aug 1 – Sep 12 | 80–110 |
| Chicory | Apr 4 | Apr 25 | May 9 | Jul 11 – Aug 22 | 60–85 |
| Chinese Cabbage | Apr 4 | Apr 25 | May 9 | Jul 4 – Aug 1 | 50–70 |
| Christmas Lima Beans | Mar 14 | May 16 | May 23 | Aug 15 – Sep 19 | 80–100 |
| Collard Greens | Apr 4 | Apr 25 | May 9 | Jul 4 – Sep 5 | 55–75 |
| Corn | — | May 16 | — | Jul 18 – Sep 12 | 60–100 |
| Cowpeas | — | May 16 | — | Jul 18 – Aug 29 | 60–90 |
| Cress | Apr 4 | Apr 25 | May 9 | May 23 – Jun 13 | 14–21 |
| Crookneck Squash | Apr 4 | May 16 | May 23 | Jul 11 – Aug 8 | 45–60 |
| Crosne | — | Apr 25 | — | Sep 26 – Nov 7 | 150–200 |
| Cucumber | Apr 4 | May 16 | May 23 | Jul 18 – Sep 12 | 50–70 |
| Daikon | — | Apr 25 | — | Jun 20 – Jul 18 | 50–70 |
| Delicata Squash | Apr 4 | May 16 | May 23 | Aug 15 – Sep 19 | 80–100 |
| Edamame | — | May 16 | — | Aug 1 – Sep 12 | 75–100 |
| Eggplant | Feb 28 | May 16 | May 23 | Aug 1 – Oct 3 | 65–85 |
| Endive | Apr 4 | Apr 25 | May 9 | Jun 27 – Aug 1 | 45–65 |
| Escarole | Apr 4 | Apr 25 | May 9 | Jul 4 – Aug 1 | 50–70 |
| Fava Beans | Apr 4 | Apr 25 | May 9 | Jul 25 – Sep 5 | 75–100 |
| Fennel | Mar 14 | May 16 | May 23 | Jul 25 – Sep 5 | 60–90 |
| Garlic | — | — | — | — | 90–240 |
| Green Beans | — | May 16 | — | Jul 11 – Sep 5 | 50–65 |
| Horseradish | — | — | May 23 | Sep 26 – Dec 5 | 120–180 |
| Hot Peppers | Feb 28 | May 16 | May 23 | Aug 1 – Nov 7 | 70–120 |
| Hubbard Squash | Apr 4 | May 16 | May 23 | Sep 5 – Oct 10 | 100–120 |
| Kabocha | Apr 4 | May 16 | May 23 | Aug 22 – Sep 19 | 85–100 |
| Kai Lan | Apr 4 | Apr 25 | May 9 | Jun 27 – Jul 25 | 45–60 |
| Kale | Apr 4 | Apr 25 | May 9 | Jul 4 – Aug 29 | 50–70 |
| Kidney Beans | — | May 16 | — | Aug 15 – Sep 19 | 85–110 |
| Kohlrabi | Apr 4 | Apr 25 | May 9 | Jun 27 – Aug 1 | 45–65 |
| Komatsuna | Apr 4 | Apr 25 | May 9 | Jun 13 – Jul 18 | 35–50 |
| Leeks | Apr 4 | Apr 25 | May 9 | Aug 8 – Oct 24 | 90–150 |
| Lentils | Apr 4 | Apr 25 | May 9 | Aug 1 – Sep 12 | 80–110 |
| Lettuce | Apr 4 | Apr 25 | May 9 | Jun 13 – Aug 22 | 30–60 |
| Lima Beans | — | May 16 | — | Jul 18 – Aug 29 | 60–90 |
| Loofah | Mar 14 | May 16 | May 23 | Sep 5 – Nov 7 | 100–150 |
| Luffa | Mar 14 | May 16 | May 23 | Aug 22 – Nov 7 | 90–150 |
| Mache | Apr 4 | Apr 25 | May 9 | Jun 20 – Jul 25 | 40–60 |
| Melon | Apr 4 | May 16 | May 23 | Aug 1 – Sep 19 | 70–100 |
| Microgreens | Apr 4 | Apr 25 | May 9 | May 16 – Jun 13 | 7–21 |
| Mitsuba | Apr 4 | Apr 25 | May 2 | Jun 27 – Aug 22 | 50–70 |
| Mizuna | Apr 4 | Apr 25 | May 9 | Jun 13 – Jul 11 | 30–45 |
| Mustard Greens | Apr 4 | Apr 25 | May 9 | Jun 13 – Aug 15 | 30–50 |
| Napa Cabbage | Apr 4 | Apr 25 | May 9 | Jul 4 – Aug 8 | 55–75 |
| New Zealand Spinach | Mar 14 | May 16 | May 23 | Jul 18 – Aug 15 | 55–70 |
| Okra | Mar 14 | May 16 | May 23 | Jul 18 – Sep 12 | 50–65 |
| Onion | Apr 4 | Apr 25 | May 9 | Aug 8 – Sep 26 | 90–120 |
| Pac Choi | Apr 4 | Apr 25 | May 9 | Jun 20 – Jul 18 | 40–55 |
| Parsnip | — | Apr 25 | — | Aug 8 – Sep 19 | 100–130 |
| Patty Pan Squash | Apr 4 | May 16 | May 23 | Jul 11 – Aug 8 | 45–60 |
| Peas | Apr 4 | Apr 25 | May 9 | Jul 4 – Aug 29 | 55–70 |
| Peppers | Feb 28 | May 16 | May 23 | Jul 25 – Oct 3 | 60–90 |
| Pole Beans | Mar 14 | May 16 | May 23 | Jul 18 – Sep 12 | 55–70 |
| Potatoes | Mar 14 | May 16 | May 23 | Aug 1 – Oct 10 | 70–120 |
| Pumpkin | Apr 4 | May 16 | May 23 | Aug 22 – Oct 10 | 85–120 |
| Purslane | Apr 4 | Apr 25 | May 9 | Jun 20 – Jul 25 | 40–60 |
| Radicchio | Apr 4 | Apr 25 | May 9 | Jul 11 – Aug 15 | 60–80 |
| Radish | — | Apr 25 | — | May 23 – Jun 13 | 22–35 |
| Rhubarb | — | — | May 30 | — | 365–730 |
| Romanesco | Apr 4 | Apr 25 | May 9 | Jul 25 – Sep 5 | 75–100 |
| Rutabaga | — | Apr 25 | — | Jul 18 – Aug 22 | 80–100 |
| Salsify | — | Apr 25 | — | Aug 8 – Sep 19 | 100–130 |
| Savoy Cabbage | Apr 4 | Apr 25 | May 9 | Jul 18 – Sep 12 | 70–110 |
| Scallions | Apr 4 | Apr 25 | May 9 | Jul 4 – Aug 1 | 50–70 |
| Scarlet Runner Beans | Mar 14 | May 16 | May 23 | Jul 25 – Aug 29 | 60–80 |
| Shallot | Apr 4 | Apr 25 | May 9 | Aug 8 – Sep 26 | 90–120 |
| Shiso | Mar 21 | May 16 | May 23 | Jul 18 – Sep 12 | 50–70 |
| Snap Peas | Mar 14 | May 16 | May 23 | Jul 18 – Sep 12 | 55–70 |
| Snow Peas | Apr 4 | Apr 25 | May 9 | Jul 4 – Aug 29 | 50–65 |
| Soybeans | — | May 16 | — | Aug 8 – Oct 3 | 80–120 |
| Spaghetti Squash | Apr 4 | May 16 | May 23 | Aug 22 – Sep 19 | 85–100 |
| Spinach | Apr 4 | Apr 25 | May 9 | Jun 13 – Aug 15 | 35–50 |
| Squash (Summer) | Apr 4 | May 16 | May 23 | Jul 11 – Sep 12 | 45–65 |
| Squash (Winter) | Apr 4 | May 16 | May 23 | Aug 15 – Oct 10 | 80–120 |
| Sunchoke | — | — | May 23 | Sep 12 – Nov 7 | 110–150 |
| Sunflower | Mar 14 | May 16 | May 23 | Aug 1 – Sep 19 | 70–100 |
| Sweet Corn | — | May 16 | — | Jul 18 – Aug 29 | 60–90 |
| Sweet Potatoes | Mar 14 | May 16 | May 23 | Aug 22 – Oct 10 | 90–120 |
| Tatsoi | Apr 4 | Apr 25 | May 9 | Jun 13 – Jul 18 | 35–50 |
| Tomatillo | Mar 14 | May 16 | May 23 | Jul 25 – Oct 3 | 60–85 |
| Tomatoes | Mar 14 | May 16 | May 23 | Jul 25 – Oct 3 | 60–85 |
| Turnip | — | Apr 25 | — | Jun 6 – Jul 11 | 40–60 |
| Watercress | Apr 4 | Apr 25 | May 9 | Jun 20 – Jul 25 | 40–60 |
| Watermelon | Apr 4 | May 16 | May 23 | Aug 1 – Sep 19 | 70–100 |
| Wax Beans | — | May 16 | — | Jul 11 – Sep 5 | 50–65 |
| Winter Melon | Mar 14 | May 16 | May 23 | Aug 22 – Oct 10 | 90–120 |
| Yard Long Beans | Mar 14 | May 16 | May 23 | Jul 18 – Aug 29 | 55–80 |
| Zucchini | Apr 4 | May 16 | May 23 | Jul 11 – Sep 5 | 45–60 |
🍓 Fruits to Grow in Washington County
27 fruits that grow well in Zone 6a with planting dates for Washington County.
Show all 27 fruits with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Harvest | Days to Maturity |
|---|---|---|---|---|---|
| Alpine Strawberries | — | — | May 30 | Aug 29 – Dec 12 | 90–180 |
| Aronia | — | — | May 30 | — | 730–1095 |
| Blackberries | — | — | May 30 | — | 365–730 |
| Blueberries | — | — | May 30 | — | 730–1095 |
| Boysenberries | — | — | May 30 | — | 365–730 |
| Cantaloupe | — | — | May 30 | Aug 8 – Sep 12 | 70–90 |
| Che Fruit | — | — | May 30 | — | 1095–1825 |
| Cranberries | — | — | May 30 | — | 730–1095 |
| Currants | — | — | May 30 | — | 730–1095 |
| Elderberries | — | — | May 30 | — | 730–1095 |
| Goji Berries | — | — | May 30 | — | 730–1095 |
| Gooseberries | — | — | May 30 | — | 730–1095 |
| Grapes | — | — | May 30 | — | 730–1095 |
| Ground Cherry | — | — | May 30 | Aug 8 – Oct 3 | 65–80 |
| Hardy Kiwi | — | — | May 30 | — | 1095–1825 |
| Haskaps | — | — | May 30 | — | 730–1095 |
| Honeydew | — | — | May 30 | Aug 22 – Oct 3 | 80–110 |
| Jostaberry | — | — | May 30 | — | 730–1095 |
| Lingonberries | — | — | May 30 | — | 730–1095 |
| Medlar | — | — | May 30 | — | 1095–1825 |
| Mulberries | — | — | May 30 | — | 730–1825 |
| Pawpaw | — | — | May 30 | — | 1095–2555 |
| Persimmon | — | — | May 30 | — | 1095–2555 |
| Quince | — | — | May 30 | — | 1095–1825 |
| Raspberries | — | — | May 30 | — | 365–730 |
| Serviceberries | — | — | May 30 | — | 730–1095 |
| Strawberries | — | — | May 30 | Aug 29 – Dec 12 | 90–365 |
🌿 Herbs to Grow in Washington County
38 herbs that grow well in Zone 6a with planting dates for Washington County.
Show all 38 herbs with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Harvest | Days to Maturity |
|---|---|---|---|---|---|
| Angelica | Apr 4 | Apr 25 | May 2 | — | 365–730 |
| Anise | Apr 4 | Apr 25 | May 2 | Aug 1 – Oct 17 | 90–120 |
| Basil | Mar 21 | May 16 | May 23 | Jul 18 – Sep 19 | 50–75 |
| Bee Balm | — | — | May 16 | Aug 15 – Oct 31 | 90–120 |
| Borage | Apr 4 | Apr 25 | May 2 | Jun 27 – Aug 15 | 50–60 |
| Caraway | Apr 4 | Apr 25 | May 2 | — | 365–450 |
| Catnip | — | — | May 16 | Jul 18 – Sep 19 | 60–80 |
| Chamomile | Apr 4 | Apr 25 | May 2 | Jul 4 – Sep 12 | 60–90 |
| Chervil | Apr 4 | Apr 25 | May 2 | Jun 13 – Aug 15 | 40–60 |
| Chives | — | — | May 16 | Jul 18 – Sep 26 | 60–90 |
| Cilantro | Apr 4 | Apr 25 | May 2 | Jun 13 – Aug 15 | 40–60 |
| Comfrey | — | — | May 16 | Jul 18 – Sep 26 | 60–90 |
| Cumin | Apr 4 | Apr 25 | May 2 | Aug 15 – Oct 17 | 100–120 |
| Dill | Apr 4 | Apr 25 | May 2 | Jun 13 – Aug 15 | 40–60 |
| Echinacea | — | — | May 16 | Sep 19 – Nov 28 | 120–180 |
| Epazote | Mar 21 | May 16 | May 23 | Jul 11 – Sep 5 | 45–60 |
| Fennel (herb) | Apr 4 | Apr 25 | May 2 | Jul 4 – Sep 12 | 60–90 |
| Feverfew | — | — | May 16 | Aug 15 – Oct 31 | 90–120 |
| Garlic Chives | — | — | May 16 | Jul 18 – Sep 26 | 60–90 |
| Horehound | — | — | May 16 | Aug 1 – Sep 26 | 75–90 |
| Hyssop | — | — | May 16 | Jul 25 – Sep 26 | 70–90 |
| Lavender | — | — | May 16 | Aug 15 – Nov 28 | 90–200 |
| Lemon Balm | — | — | May 16 | Jul 18 – Sep 5 | 60–70 |
| Lemon Thyme | — | — | May 16 | Jul 25 – Sep 26 | 70–90 |
| Lovage | — | — | May 16 | Jul 25 – Sep 26 | 70–90 |
| Marjoram | — | — | May 16 | Jul 18 – Sep 26 | 60–90 |
| Mint | — | — | May 16 | Jul 18 – Sep 26 | 60–90 |
| Oregano | — | — | May 16 | Jul 18 – Sep 26 | 60–90 |
| Parsley | Apr 4 | Apr 25 | May 2 | Jul 4 – Sep 5 | 60–80 |
| Rue | — | — | May 16 | Jul 25 – Sep 26 | 70–90 |
| Sage | — | — | May 16 | Aug 1 – Sep 26 | 75–90 |
| Savory | — | — | May 16 | Jul 11 – Sep 5 | 50–70 |
| Sorrel | Apr 4 | Apr 25 | May 2 | Jun 13 – Aug 15 | 40–60 |
| Tarragon | — | — | May 16 | Jul 18 – Sep 26 | 60–90 |
| Thai Basil | Mar 21 | May 16 | May 23 | Jul 18 – Sep 19 | 50–75 |
| Thyme | — | — | May 16 | Jul 25 – Sep 26 | 70–90 |
| Valerian | — | — | May 16 | Sep 19 – Nov 28 | 120–180 |
| Yarrow | — | — | May 16 | Aug 15 – Oct 31 | 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, ID?
Washington County is in USDA Hardiness Zone 6a. 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, ID?
Based on 30 years of NOAA weather station data, the median last spring frost in Washington County falls around May 9. In 8 out of 10 years, last frost lands between April 16 and June 7 — a 52-day window of variability. Use June 7 as your conservative safe-to-plant date for frost-sensitive crops.
When is the first fall frost in Washington County, ID?
The median first fall frost in Washington County arrives around October 1. In cold years it can arrive as early as September 12; in mild years as late as October 21. 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 145 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 8.53 days per decade.
What is the soil like in Washington County for gardening?
Washington County has predominantly Loam soil with a pH range of 6.2–7.8 and Excessively 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 Potatoes, Hay, Wheat. 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 38/100 (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.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Washington County gardeners in Zone 6a 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.
