When to Plant Tomatoes in King County, WA
Tomatoes are the most popular home garden crop, available in thousands of varieties from tiny cherries to massive beefsteaks. They are warm-season plants needing full sun.
King County, Washington 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 feet, King County receives approximately 37.6 inches of rainfall annually with predominantly silt loam soil. Summer highs average 89°F, providing good warmth for Tomatoes during the growing season.
King County Soil Profile
Soil Type
Silt Loam
Soil pH
5.7-6.4
Drainage
Well Drained
How Much Tomatoes to Grow
For a family of 4, plant approximately 12 tomatoes plants in about 24 sq ft. In King County's 206-day season, you'll have plenty of time for a full harvest. Plan your garden layout →
Monthly Watering Guide for Tomatoes
Tomatoes needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Tomatoes Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 5.9" | 0" | ❄️ Dormant |
| Feb | — | 4.5" | 0" | ❄️ Dormant |
| Mar | — | 3.4" | 0" | ❄️ Dormant |
| Apr | 4.3" | 2.9" | 1.4" | 💧 Light watering |
| May | 4.3" | 2" | 2.3" | 🚿 Regular watering |
| Jun | 4.3" | 1.3" | 3" | 🚿 Regular watering |
| Jul | 4.3" | 0.6" | 3.7" | 🚿 Regular watering |
| Aug | 4.3" | 0.7" | 3.6" | 🚿 Regular watering |
| Sep | 4.3" | 1.6" | 2.7" | 🚿 Regular watering |
| Oct | 4.3" | 3.4" | 0.9" | 💧 Light watering |
| Nov | — | 5.6" | 0" | ❄️ Dormant |
| Dec | — | 5.7" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in King County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Tomatoes Planting Timeline — King County, WA
Tomatoes Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | February 24 | Feb 24 – Mar 10 |
| Transplant Outdoors | April 14 | Apr 14 – Apr 28 |
| Direct Sow | April 7 | Apr 7 – Apr 28 |
| Harvest | June 16 | Jun 16 – Aug 25 |
Plant 0.5" deep · 24" apart · Rows 36" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | Start Indoors |
| March | Start Indoors |
| April | Transplant Outdoors Direct Sow |
| May | — |
| June | Harvest |
| July | Harvest |
| August | Harvest |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
Moderate — regular watering
📅 Days to Maturity
60–85 days
🧪 Soil pH
Needs 6–7 · Your soil: N/A
🗺️ USDA Zone
Zone 9a
📆 Growing Season
206 days in King County
Growing Tips for King County
Start seeds indoors 6-8 weeks before last frost. Bury transplants deep to encourage rooting along the stem. Provide consistent moisture to prevent blossom end rot and cracking.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Isolate 25 ft between varieties for purity. Use open-pollinated varieties for true-to-type seeds.
Tomatoes in Other Locations
Frequently Asked Questions
When should I plant Tomatoes in King County, WA?
King County is in Zone 9a with an average last frost of April 7. Plan your Tomatoes planting based on this frost date — see the calendar above for exact timing.
What planting zone is King County, WA?
King County, Washington is in USDA Hardiness Zone 9a. The average last spring frost is April 7 and first fall frost is October 30.
Your King County Garden Planner — Free
A 22-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.