King County, WA — Planting Guide
Your May planting checklist for King County, Washington
Welcome to May in Zone 9a. These are the moves that will have the biggest impact on your growing season.
-
Fire up the seed-starting tray: basil, cucumber, and kale
Your window is short. These crops want several weeks of indoor growth before they go outside.
-
Bring in the carrots, lettuce, and radish
Morning harvests are best — cooler temperatures mean crisper produce and longer fridge life.
Get ahead of June
- First harvests: basil, carrots, and cucumber
King County is in USDA Zone 9a. The average last spring frost is April 7 and the first fall frost is October 30, giving you a growing season of approximately 206 days.
At an elevation of 258 ft, King County receives approximately 37.6 in of rainfall annually. Summer highs average 89°F with winter lows around 43°F. The predominant soil type is Silt Loam.
Based on 31 years of NOAA climate station data, the last frost date here varies by 69 days year to year — ranging from March 11 in warm years to May 20 in cold years. The growing season is trending longer by about 3.16 days per decade. King County scores 61/100 (Good) on the Microclimate Index.
🌡️ Zone
9a (°F to °F min)
❄️ Last Frost
April 7
🍂 First Frost
October 30
📅 Growing Season
206 days
⛰️ Elevation
258 ft
🌧️ Annual Rainfall
37.6 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 | 5.9 in | 17 days | — | None |
| Feb | 4.5 in | 16 days | — | Low |
| Mar | 3.4 in | 15 days | 0.9 in | Moderate |
| Apr | 2.9 in | 14 days | 1.4 in | Moderate |
| May | 2 in | 10 days | 2.3 in | High |
| Jun | 1.3 in | 7 days | 3 in | High |
| Jul | 0.6 in | 3 days | 3.7 in | Critical |
| Aug | 0.7 in | 3 days | 3.6 in | Critical |
| Sep | 1.6 in | 5 days | 2.7 in | High |
| Oct | 3.4 in | 11 days | 0.9 in | Moderate |
| Nov | 5.6 in | 17 days | — | Low |
| Dec | 5.7 in | 16 days | — | None |
Annual total: 37.6 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.
King County Soil Profile
Soil Type
Silt Loam
Soil pH
5.7-6.4
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 20 | Nov 21 | 185 days |
| Cautious | Apr 26 | Nov 9 | 197 days |
| Average year | Apr 7 | Oct 30 | 206 days |
| Optimistic | Mar 24 | Oct 14 | 204 days |
| Aggressive (risky) | Mar 11 | Sep 29 | 202 days |
Not very — frost dates can vary by ±69 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 3.2 days per decade). Spring is arriving earlier than it used to. Good news for gardeners.
Gardening Difficulty Score
King County offers good growing conditions. A little planning around frost dates goes a long way.
Local Gardening Help in King 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 King County's climate and soil.
County Extension Office
King County Washington State University Extension Extension Office
Phone: 509-335-2811
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 King County
Finding local nurseries & garden centers in King County
Why Buy Local
Local nurseries carry plants that are proven to grow in your area. Staff can give you advice specific to King 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 King County WA" or "garden center King 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 King County WA" or check your extension office and local parks department. Facebook groups like "King County Gardeners" or "Washington 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 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 | 2.2 hr | Short day |
| February | 10 hr | 3 hr | Short day |
| March | 11.6 hr | 4.2 hr | Short day |
| April | 13.4 hr | 5.8 hr | Neutral |
| May | 14.9 hr | 7.2 hr | Long day |
| June | 15.7 hr | 8.5 hr | Long day |
| July | 15.4 hr | 11 hr | Long day |
| August | 14.1 hr | 9.9 hr | Long day |
| September | 12.3 hr | 6.9 hr | Neutral |
| October | 10.6 hr | 4.1 hr | Short day |
| November | 9 hr | 2.2 hr | Short day |
| December | 8.3 hr | 1.9 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 Apr through Oct.
Best Month to Compost
May
Microbial activity peaks when soil is warm.
Active Composting
8 months
Nearly year-round composting.
View detailed monthly data
| Month | Soil 4" Deep | Soil 8" Deep | Compost Activity | Time to Finish |
|---|---|---|---|---|
| Jan | 45°F | 50°F | 🐢 Slow | ~24 weeks |
| Feb | 45°F | 50°F | 🐢 Slow | ~24 weeks |
| Mar | 50°F | 53°F | 🐢 Slow | ~24 weeks |
| Apr | 61°F | 61°F | ♻️ Active | ~14 weeks |
| May | 69°F | 68°F | 🔥 Peak | ~8 weeks |
| Jun | 79°F | 77°F | 🔥 Peak | ~8 weeks |
| Jul | 89°F | 83°F | 🔥 Peak | ~8 weeks |
| Aug | 90°F | 87°F | 🔥 Peak | ~8 weeks |
| Sep | 85°F | 84°F | 🔥 Peak | ~8 weeks |
| Oct | 73°F | 75°F | 🔥 Peak | ~8 weeks |
| Nov | 59°F | 65°F | ♻️ Active | ~14 weeks |
| Dec | 48°F | 54°F | 🐢 Slow | ~24 weeks |
Highlighted rows = soil 60°F+ (safe for warm-season transplants). Compost finishes fastest during peak activity months.
Pest & Disease Pressure in King County
Computed from local climate patterns — warmer, humid conditions increase pest generations and fungal disease risk.
Insect Pest Pressure
High — expect multiple pest generations. Preventative measures essential.
Disease Risk
High fungal/bacterial risk. Space plants for airflow, water at soil level.
Seasonal Risk
View 6 common pests in your area
| Pest | Risk Level | Peak Months |
|---|---|---|
| Aphids | High | Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov |
| Squash vine borers | High | May, Jun, Jul |
| Stink bugs | High | Apr, May, Jun, Jul, Aug, Sep, Oct |
| Whiteflies | Moderate | May, Jun, Jul, Aug, Sep, Oct |
| Spider mites | High | Jun, Jul, Aug, Sep |
| Fire ants | Moderate | Mar, Apr, May, Jun, Jul, Aug, Sep, Oct |
Organic pest management tips
- Install physical barriers: floating row covers, copper tape for slugs, mesh netting
- Apply Bt (Bacillus thuringiensis) for caterpillar control — safe for beneficial insects
- Use kaolin clay spray to deter a wide range of insects on fruiting crops
- Release beneficial insects: ladybugs for aphids, parasitic wasps for caterpillars
- Apply neem oil weekly during high-pressure months
- Mulch heavily (3-4 inches) to reduce soil-borne disease splash
Cover Crops for King County
Cover crops protect bare soil, fix nitrogen, suppress weeds, and improve soil structure — with county-specific planting dates.
Spring Cover Crops (4 options) — Build soil before the main growing season
| Crop | Plant By | Terminate | N-Fixing | Soil Benefit |
|---|---|---|---|---|
| Buckwheat | Apr 19 | Sep 4 | — | Rapid growth, attracts pollinators, suppresses weeds |
| Cowpeas (southern peas) | Apr 15 | Aug 28 | ✓ Yes | Excellent nitrogen fixer for warm climates, edible |
| Sorghum-sudan grass | Apr 9 | Aug 28 | — | Massive biomass, breaks compaction, suppresses nematodes |
| White clover | Mar 9 | Aug 28 | ✓ 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 | Apr 24 | Oct 2 | — | 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 19 | Mar 24 | ✓ Yes | Fixes nitrogen, good for heavy clay soils |
| Crimson clover | Aug 24 | Mar 17 | ✓ Yes | Fixes nitrogen, attracts pollinators in spring |
| Daikon radish | Sep 17 | Mar 17 | — | Deep taproot breaks compaction, excellent for clay soils |
| Hairy vetch | Aug 12 | Mar 17 | ✓ Yes | Excellent nitrogen fixer, good for depleted soils |
| Oats | Sep 21 | Mar 17 | — | Quick biomass, winterkills in cold zones — no spring tillage needed |
| Winter rye | Jul 24 | Mar 24 | — | Suppresses weeds, prevents erosion, breaks up compacted soil |
| Winter wheat | Jul 22 | Mar 17 | — | 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: 8 mph
Fall: 10 mph Winter: 12 mph
Prevailing wind: SW. Moderate wind — consider a temporary windbreak for young seedlings.
Windbreak Benefit
4.7/10
Moderately beneficial — a simple fence or trellis can protect delicate crops from wind stress.
Frost Pocket Risk
Moderate
Some terrain variation (528 ft range). Garden on slopes or higher ground if possible to avoid late-season frost pockets.
Rainwater Harvesting Potential
How much water you can collect, when to collect it, and what size system you need for your garden.
Annual Collection
18,739 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 2,250 gal tank.
Legal Status
Unrestricted
Rainwater harvesting is fully legal in your state with no restrictions.
Best Collection Months
Jan, Feb, Nov, Dec
Highest rainfall months — your barrels will fill up quickly during these months.
Months to Draw From Storage
Jul, Aug
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 37.6 inches of rain per year
- A 1,000 sq ft roof can collect roughly 18,739 gallons annually
- Rainwater harvesting is fully legal in your state
- Use a first-flush diverter to keep roof debris out of your collection
Soil & Growing Conditions in King County
Soil Type
Silt Loam
Soil pH 5.7–6.4 · 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. (37.6 in. annual rainfall)
Season Tips
206-day frost-free season
Plenty of time for warm-season crops. Start heat-lovers indoors 6–8 weeks before last frost to maximise your harvest window.
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
Reduce heat stress and sun scorch in hot climates with UV-stabilized shade cloth.
Test your soil pH, nitrogen, phosphorus, and potassium levels before planting.
Get instant, accurate soil pH readings to fine-tune your amendments.
🥬 Vegetables to Grow in King County
115 vegetables that grow well in Zone 9a with planting dates for King County.
Show all 115 vegetables with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Harvest | Days to Maturity |
|---|---|---|---|---|---|
| Acorn Squash | Mar 10 | Apr 7 | Apr 14 | Jul 7 – Aug 11 | 80–100 |
| Amaranth | Feb 24 | Apr 7 | Apr 14 | Jul 14 – Sep 1 | 90–120 |
| Artichoke | — | — | Apr 21 | Aug 25 – Nov 3 | 120–180 |
| Arugula | Mar 10 | Mar 17 | Apr 7 | May 12 – Jul 14 | 30–50 |
| Asparagus | — | — | Apr 21 | — | 730–1095 |
| Beets | — | Mar 17 | — | May 12 – Jun 9 | 50–70 |
| Belgian Endive | Mar 10 | Mar 17 | Apr 7 | Jul 28 – Sep 22 | 110–150 |
| Bitter Melon | Feb 24 | Apr 7 | Apr 14 | Jun 16 – Jul 28 | 60–90 |
| Black Beans | — | Apr 14 | — | Jul 14 – Sep 1 | 90–120 |
| Bok Choy | Mar 10 | Mar 17 | Apr 7 | May 19 – Jun 23 | 40–60 |
| Broccoli | Mar 10 | Mar 17 | Apr 7 | Jun 9 – Jul 21 | 60–90 |
| Broccoli Rabe | Mar 10 | Mar 17 | Apr 7 | May 19 – Jun 23 | 40–60 |
| Brussels Sprouts | Mar 10 | Mar 17 | Apr 7 | Jul 7 – Sep 1 | 90–130 |
| Butternut Squash | Mar 10 | Apr 7 | Apr 14 | Jul 14 – Aug 18 | 85–110 |
| Cabbage | Mar 10 | Mar 17 | Apr 7 | Jun 9 – Aug 4 | 60–100 |
| Calabash | Feb 24 | Apr 7 | Apr 14 | Jul 7 – Sep 1 | 80–120 |
| Cardoon | — | — | Apr 21 | Aug 25 – Oct 6 | 120–150 |
| Carrots | — | Mar 17 | — | May 19 – Jun 23 | 60–80 |
| Cauliflower | Mar 10 | Mar 17 | Apr 7 | Jun 2 – Aug 4 | 55–100 |
| Celeriac | Mar 10 | Mar 17 | Apr 7 | Jul 21 – Aug 25 | 100–120 |
| Celery | Mar 10 | Mar 17 | Apr 7 | Jun 30 – Aug 25 | 80–120 |
| Celtuce | Mar 10 | Mar 17 | Apr 7 | Jun 9 – Jul 21 | 60–90 |
| Chard | Mar 10 | Mar 17 | Apr 7 | Jun 2 – Jul 21 | 50–60 |
| Chayote | Feb 24 | Apr 7 | Apr 14 | Aug 18 – Oct 27 | 120–180 |
| Chickpeas | Mar 10 | Mar 17 | Apr 7 | Jun 30 – Aug 11 | 80–110 |
| Chicory | Mar 10 | Mar 17 | Apr 7 | Jun 9 – Jul 21 | 60–85 |
| Chinese Cabbage | Mar 10 | Mar 17 | Apr 7 | Jun 2 – Jun 30 | 50–70 |
| Christmas Lima Beans | Feb 24 | Apr 7 | Apr 14 | Jul 7 – Aug 11 | 80–100 |
| Collard Greens | Mar 10 | Mar 17 | Apr 7 | Jun 2 – Aug 4 | 55–75 |
| Corn | — | Apr 14 | — | Jun 16 – Aug 11 | 60–100 |
| Cowpeas | — | Apr 14 | — | Jun 16 – Jul 28 | 60–90 |
| Cress | Mar 10 | Mar 17 | Apr 7 | Apr 21 – May 12 | 14–21 |
| Crookneck Squash | Mar 10 | Apr 7 | Apr 14 | Jun 2 – Jun 30 | 45–60 |
| Crosne | — | Mar 17 | — | Aug 18 – Oct 20 | 150–200 |
| Cucumber | Mar 10 | Apr 7 | Apr 14 | Jun 9 – Aug 4 | 50–70 |
| Daikon | — | Mar 17 | — | May 12 – Jun 9 | 50–70 |
| Delicata Squash | Mar 10 | Apr 7 | Apr 14 | Jul 7 – Aug 11 | 80–100 |
| Edamame | — | Apr 14 | — | Jun 30 – Aug 11 | 75–100 |
| Eggplant | Feb 24 | Apr 7 | Apr 14 | Jun 23 – Aug 25 | 65–85 |
| Endive | Mar 10 | Mar 17 | Apr 7 | May 26 – Jun 30 | 45–65 |
| Escarole | Mar 10 | Mar 17 | Apr 7 | Jun 2 – Jun 30 | 50–70 |
| Fava Beans | Mar 10 | Mar 17 | Apr 7 | Jun 23 – Aug 4 | 75–100 |
| Fennel | Feb 24 | Apr 7 | Apr 14 | Jun 16 – Jul 28 | 60–90 |
| Garlic | — | — | — | — | 90–240 |
| Ginger | Feb 24 | Apr 7 | Apr 14 | Dec 15 – Feb 9 | 240–300 |
| Green Beans | — | Apr 14 | — | Jun 9 – Aug 4 | 50–65 |
| Horseradish | — | — | Apr 21 | Aug 25 – Nov 3 | 120–180 |
| Hot Peppers | Feb 24 | Apr 7 | Apr 14 | Jun 23 – Sep 29 | 70–120 |
| Hubbard Squash | Mar 10 | Apr 7 | Apr 14 | Jul 28 – Sep 1 | 100–120 |
| Jicama | Feb 24 | Apr 7 | Apr 14 | Aug 18 – Oct 27 | 120–180 |
| Kabocha | Mar 10 | Apr 7 | Apr 14 | Jul 14 – Aug 11 | 85–100 |
| Kai Lan | Mar 10 | Mar 17 | Apr 7 | May 26 – Jun 23 | 45–60 |
| Kale | Mar 10 | Mar 17 | Apr 7 | Jun 2 – Jul 28 | 50–70 |
| Kidney Beans | — | Apr 14 | — | Jul 14 – Aug 18 | 85–110 |
| Kohlrabi | Mar 10 | Mar 17 | Apr 7 | May 26 – Jun 30 | 45–65 |
| Komatsuna | Mar 10 | Mar 17 | Apr 7 | May 12 – Jun 16 | 35–50 |
| Leeks | Mar 10 | Mar 17 | Apr 7 | Jul 7 – Sep 22 | 90–150 |
| Lentils | Mar 10 | Mar 17 | Apr 7 | Jun 30 – Aug 11 | 80–110 |
| Lettuce | Mar 10 | Mar 17 | Apr 7 | May 12 – Jul 21 | 30–60 |
| Lima Beans | — | Apr 14 | — | Jun 16 – Jul 28 | 60–90 |
| Loofah | Feb 24 | Apr 7 | Apr 14 | Jul 28 – Sep 29 | 100–150 |
| Luffa | Feb 24 | Apr 7 | Apr 14 | Jul 14 – Sep 29 | 90–150 |
| Mache | Mar 10 | Mar 17 | Apr 7 | May 19 – Jun 23 | 40–60 |
| Malabar Spinach | Feb 24 | Apr 7 | Apr 14 | Jun 9 – Jul 7 | 55–70 |
| Melon | Mar 10 | Apr 7 | Apr 14 | Jun 23 – Aug 11 | 70–100 |
| Microgreens | Mar 10 | Mar 17 | Apr 7 | Apr 14 – May 12 | 7–21 |
| Mitsuba | Mar 10 | Mar 17 | Mar 31 | May 26 – Jul 21 | 50–70 |
| Mizuna | Mar 10 | Mar 17 | Apr 7 | May 12 – Jun 9 | 30–45 |
| Mustard Greens | Mar 10 | Mar 17 | Apr 7 | May 12 – Jul 14 | 30–50 |
| Napa Cabbage | Mar 10 | Mar 17 | Apr 7 | Jun 2 – Jul 7 | 55–75 |
| New Zealand Spinach | Feb 24 | Apr 7 | Apr 14 | Jun 9 – Jul 7 | 55–70 |
| Okra | Feb 24 | Apr 7 | Apr 14 | Jun 9 – Aug 4 | 50–65 |
| Onion | Mar 10 | Mar 17 | Apr 7 | Jul 7 – Aug 25 | 90–120 |
| Pac Choi | Mar 10 | Mar 17 | Apr 7 | May 19 – Jun 16 | 40–55 |
| Parsnip | — | Mar 17 | — | Jun 30 – Aug 11 | 100–130 |
| Patty Pan Squash | Mar 10 | Apr 7 | Apr 14 | Jun 2 – Jun 30 | 45–60 |
| Peas | Mar 10 | Mar 17 | Apr 7 | Jun 2 – Jul 28 | 55–70 |
| Peppers | Feb 24 | Apr 7 | Apr 14 | Jun 16 – Aug 25 | 60–90 |
| Pole Beans | Feb 24 | Apr 7 | Apr 14 | Jun 9 – Aug 4 | 55–70 |
| Potatoes | Feb 24 | Apr 7 | Apr 14 | Jun 23 – Sep 1 | 70–120 |
| Pumpkin | Mar 10 | Apr 7 | Apr 14 | Jul 14 – Sep 1 | 85–120 |
| Purslane | Mar 10 | Mar 17 | Apr 7 | May 19 – Jun 23 | 40–60 |
| Radicchio | Mar 10 | Mar 17 | Apr 7 | Jun 9 – Jul 14 | 60–80 |
| Radish | — | Mar 17 | — | Apr 14 – May 5 | 22–35 |
| Romanesco | Mar 10 | Mar 17 | Apr 7 | Jun 23 – Aug 4 | 75–100 |
| Rutabaga | — | Mar 17 | — | Jun 9 – Jul 14 | 80–100 |
| Salsify | — | Mar 17 | — | Jun 30 – Aug 11 | 100–130 |
| Savoy Cabbage | Mar 10 | Mar 17 | Apr 7 | Jun 16 – Aug 11 | 70–110 |
| Scallions | Mar 10 | Mar 17 | Apr 7 | Jun 2 – Jun 30 | 50–70 |
| Scarlet Runner Beans | Feb 24 | Apr 7 | Apr 14 | Jun 16 – Jul 21 | 60–80 |
| Shallot | Mar 10 | Mar 17 | Apr 7 | Jul 7 – Aug 25 | 90–120 |
| Shiso | Feb 24 | Apr 14 | Apr 14 | Jun 9 – Aug 4 | 50–70 |
| Snap Peas | Feb 24 | Apr 7 | Apr 14 | Jun 9 – Aug 4 | 55–70 |
| Snow Peas | Mar 10 | Mar 17 | Apr 7 | Jun 2 – Jul 28 | 50–65 |
| Soybeans | — | Apr 14 | — | Jul 7 – Sep 1 | 80–120 |
| Spaghetti Squash | Mar 10 | Apr 7 | Apr 14 | Jul 14 – Aug 11 | 85–100 |
| Spinach | Mar 10 | Mar 17 | Apr 7 | May 12 – Jul 14 | 35–50 |
| Squash (Summer) | Mar 10 | Apr 7 | Apr 14 | Jun 2 – Aug 4 | 45–65 |
| Squash (Winter) | Mar 10 | Apr 7 | Apr 14 | Jul 7 – Sep 1 | 80–120 |
| Sunchoke | — | — | Apr 21 | Aug 11 – Oct 6 | 110–150 |
| Sunflower | Feb 24 | Apr 7 | Apr 14 | Jun 23 – Aug 11 | 70–100 |
| Sweet Corn | — | Apr 14 | — | Jun 16 – Jul 28 | 60–90 |
| Sweet Potatoes | Feb 24 | Apr 7 | Apr 14 | Jul 14 – Sep 1 | 90–120 |
| Tatsoi | Mar 10 | Mar 17 | Apr 7 | May 12 – Jun 16 | 35–50 |
| Tomatillo | Feb 24 | Apr 7 | Apr 14 | Jun 16 – Aug 25 | 60–85 |
| Tomatoes | Feb 24 | Apr 7 | Apr 14 | Jun 16 – Aug 25 | 60–85 |
| Turmeric | Feb 24 | Apr 7 | Apr 14 | Dec 15 – Feb 9 | 240–300 |
| Turnip | — | Mar 17 | — | Apr 28 – Jun 2 | 40–60 |
| Watercress | Mar 10 | Mar 17 | Apr 7 | May 19 – Jun 23 | 40–60 |
| Watermelon | Mar 10 | Apr 7 | Apr 14 | Jun 23 – Aug 11 | 70–100 |
| Wax Beans | — | Apr 14 | — | Jun 9 – Aug 4 | 50–65 |
| Winter Melon | Feb 24 | Apr 7 | Apr 14 | Jul 14 – Sep 1 | 90–120 |
| Yam | Feb 24 | Apr 7 | Apr 14 | Oct 13 – Feb 9 | 180–330 |
| Yard Long Beans | Feb 24 | Apr 7 | Apr 14 | Jun 9 – Jul 21 | 55–80 |
| Zucchini | Mar 10 | Apr 7 | Apr 14 | Jun 2 – Jul 28 | 45–60 |
🍓 Fruits to Grow in King County
24 fruits that grow well in Zone 9a with planting dates for King County.
Show all 24 fruits with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Harvest | Days to Maturity |
|---|---|---|---|---|---|
| Alpine Strawberries | — | — | Apr 21 | Jul 21 – Nov 3 | 90–180 |
| Blackberries | — | — | Apr 21 | — | 365–730 |
| Boysenberries | — | — | Apr 21 | — | 365–730 |
| Cantaloupe | — | — | Apr 21 | Jun 30 – Aug 4 | 70–90 |
| Che Fruit | — | — | Apr 21 | — | 1095–1825 |
| Dragon Fruit | — | — | Apr 21 | — | 365–730 |
| Elderberries | — | — | Apr 21 | — | 730–1095 |
| Figs | — | — | Apr 21 | — | 730–1825 |
| Goji Berries | — | — | Apr 21 | — | 730–1095 |
| Grapes | — | — | Apr 21 | — | 730–1095 |
| Ground Cherry | — | — | Apr 21 | Jun 30 – Aug 25 | 65–80 |
| Guava | — | — | Apr 21 | — | 365–730 |
| Honeydew | — | — | Apr 21 | Jul 14 – Aug 25 | 80–110 |
| Kiwi | — | — | Apr 21 | — | 1095–1825 |
| Loquat | — | — | Apr 21 | — | 730–1825 |
| Mulberries | — | — | Apr 21 | — | 730–1825 |
| Passion Fruit | — | — | Apr 21 | — | 365–545 |
| Pawpaw | — | — | Apr 21 | — | 1095–2555 |
| Persimmon | — | — | Apr 21 | — | 1095–2555 |
| Pomegranate | — | — | Apr 21 | — | 730–1095 |
| Quince | — | — | Apr 21 | — | 1095–1825 |
| Raspberries | — | — | Apr 21 | — | 365–730 |
| Serviceberries | — | — | Apr 21 | — | 730–1095 |
| Strawberries | — | — | Apr 21 | Jul 21 – Feb 16 | 90–365 |
🌿 Herbs to Grow in King County
40 herbs that grow well in Zone 9a with planting dates for King County.
Show all 40 herbs with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Harvest | Days to Maturity |
|---|---|---|---|---|---|
| Anise | Mar 10 | Mar 17 | Mar 31 | Jun 30 – Sep 15 | 90–120 |
| Basil | Feb 24 | Apr 14 | Apr 14 | Jun 9 – Aug 11 | 50–75 |
| Bee Balm | — | — | Apr 14 | Jul 14 – Sep 29 | 90–120 |
| Borage | Mar 10 | Mar 17 | Mar 31 | May 26 – Jul 14 | 50–60 |
| Caraway | Mar 10 | Mar 17 | Mar 31 | — | 365–450 |
| Catnip | — | — | Apr 14 | Jun 16 – Aug 18 | 60–80 |
| Chamomile | Mar 10 | Mar 17 | Mar 31 | Jun 2 – Aug 11 | 60–90 |
| Chervil | Mar 10 | Mar 17 | Mar 31 | May 12 – Jul 14 | 40–60 |
| Chives | — | — | Apr 14 | Jun 16 – Aug 25 | 60–90 |
| Cilantro | Mar 10 | Mar 17 | Mar 31 | May 12 – Jul 14 | 40–60 |
| Comfrey | — | — | Apr 14 | Jun 16 – Aug 25 | 60–90 |
| Cumin | Mar 10 | Mar 17 | Mar 31 | Jul 14 – Sep 15 | 100–120 |
| Dill | Mar 10 | Mar 17 | Mar 31 | May 12 – Jul 14 | 40–60 |
| Echinacea | — | — | Apr 14 | Aug 18 – Nov 24 | 120–180 |
| Epazote | Feb 24 | Apr 14 | Apr 14 | Jun 2 – Jul 28 | 45–60 |
| Fennel (herb) | Mar 10 | Mar 17 | Mar 31 | Jun 2 – Aug 11 | 60–90 |
| Feverfew | — | — | Apr 14 | Jul 14 – Sep 29 | 90–120 |
| Garlic Chives | — | — | Apr 14 | Jun 16 – Aug 25 | 60–90 |
| Horehound | — | — | Apr 14 | Jun 30 – Aug 25 | 75–90 |
| Hyssop | — | — | Apr 14 | Jun 23 – Aug 25 | 70–90 |
| Lavender | — | — | Apr 14 | Jul 14 – Dec 15 | 90–200 |
| Lemon Balm | — | — | Apr 14 | Jun 16 – Aug 4 | 60–70 |
| Lemon Thyme | — | — | Apr 14 | Jun 23 – Aug 25 | 70–90 |
| Lemon Verbena | Feb 24 | Apr 14 | Apr 14 | Jun 16 – Aug 25 | 60–90 |
| Lemongrass | Feb 24 | Apr 14 | Apr 14 | Jun 30 – Sep 29 | 75–120 |
| Marjoram | — | — | Apr 14 | Jun 16 – Aug 25 | 60–90 |
| Mint | — | — | Apr 14 | Jun 16 – Aug 25 | 60–90 |
| Oregano | — | — | Apr 14 | Jun 16 – Aug 25 | 60–90 |
| Parsley | Mar 10 | Mar 17 | Mar 31 | Jun 2 – Aug 4 | 60–80 |
| Rosemary | — | — | Apr 14 | Jul 7 – Nov 24 | 80–180 |
| Rue | — | — | Apr 14 | Jun 23 – Aug 25 | 70–90 |
| Sage | — | — | Apr 14 | Jun 30 – Aug 25 | 75–90 |
| Savory | — | — | Apr 14 | Jun 9 – Aug 4 | 50–70 |
| Sorrel | Mar 10 | Mar 17 | Mar 31 | May 12 – Jul 14 | 40–60 |
| Stevia | Feb 24 | Apr 14 | Apr 14 | Jun 16 – Aug 25 | 60–90 |
| Tarragon | — | — | Apr 14 | Jun 16 – Aug 25 | 60–90 |
| Thai Basil | Feb 24 | Apr 14 | Apr 14 | Jun 9 – Aug 11 | 50–75 |
| Thyme | — | — | Apr 14 | Jun 23 – Aug 25 | 70–90 |
| Valerian | — | — | Apr 14 | Aug 18 – Nov 24 | 120–180 |
| Yarrow | — | — | Apr 14 | Jul 14 – Sep 29 | 90–120 |
Monthly Planting Guide for King County
Gardening Guides & Resources
Helpful guides from The Ultimate Homestead to improve your garden in King County.
Frequently Asked Questions
What planting zone is King County, WA?
King County is in USDA Hardiness Zone 9a. 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 King County, WA?
Based on 31 years of NOAA weather station data, the median last spring frost in King County falls around April 7. In 8 out of 10 years, last frost lands between March 11 and May 20 — a 69-day window of variability. Use May 20 as your conservative safe-to-plant date for frost-sensitive crops.
When is the first fall frost in King County, WA?
The median first fall frost in King County arrives around October 30. In cold years it can arrive as early as September 29; in mild years as late as November 21. Harvest or protect frost-sensitive crops — tomatoes, peppers, basil, squash — before this date.
How long is the growing season in King County?
King County has a frost-free growing season of approximately 206 days. This long season supports multiple succession plantings and warm-season crops that need extended heat, like sweet potatoes and melons. Climate records show the growing season is trending longer by about 3.16 days per decade.
What is the soil like in King County for gardening?
King County has predominantly Silt Loam soil with a pH range of 5.7–6.4 and Well Drained drainage. Most vegetables and herbs grow well with standard composting and seasonal soil amendment.
What is grown commercially in King County?
King County has commercial agriculture that includes Wheat, Hay, Apples, Potatoes, Berries. These crops reflect the local climate and soil conditions — what succeeds commercially often translates well to home gardens in the same area.
Is King County a good location for home gardening?
King 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 King County Garden Planner — Free
A 24-page printable planner built for King County (Zone 9a). 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