When to Plant Pumpkins in Washington
Published: April 24, 2026
Washington gardeners in Zone 4b have a 21-week frost-free window for pumpkin (May 7 to October 1). Warm-season crops like pumpkin must be started indoors early to maximize the short window — Washington's late spring and early fall frost dates leave little room for error. This guide gives exact dates for Washington based on your local frost calendar.
Pumpkin Planting Dates for Washington
| Start seeds indoors | April 16–23 |
| Last frost (average) | May 7 |
| Transplant outdoors | May 14–24 |
| Direct sow outdoors | May 14–24 |
| Expect first harvest | July 28 – August 22 |
| First fall frost (average) | October 1 |
⚠ Count back 75–100 days from desired harvest date. For Halloween harvest, plant late June to mid-July. Plant 1–2 weeks after last frost.
Growing Pumpkins in Washington's Climate
Washington's cold Zone 4b climate puts warm-season pumpkin at the edge of viability — but the edge is workable with good planning. Starting seeds indoors under lights in late winter is the most important step; skipping this puts the whole harvest at risk from the short outdoor growing window.
Season extenders pay for themselves many times over in Washington. Row covers placed over transplants in early spring add 5°F to 8°F of protection and can extend the season two to three weeks on each end. Black plastic mulch warms the soil to the temperatures pumpkin needs for aggressive root growth.
Common pumpkin pests to watch for in Washington include Squash Vine Borer and Squash Bug. The first line of defense is companion planting: Corn and Bush Bean planted nearby discourage several of these pests by confusing host-plant identification or repelling adults before they can lay eggs. Weekly garden walks in the early morning catch problems when they're still manageable.
Pumpkin Garden Calendar for Washington
| Month | Task | Notes |
|---|---|---|
| January | — | Dormant season |
| February | — | Dormant season |
| March | — | Dormant season |
| April | Start seeds indoors | Use grow lights; warm soil to 70–75°F for best germination |
| May ← | Transplant outdoors | Soil temp must be 60°F+; nighttime lows above 50°F |
| June | Peak growth; water 1 inch/week | Monitor for pests daily; stake or support as needed |
| July | Continue care | Consistent watering; remove yellow leaves |
| August | — | Dormant season |
| September | — | Dormant season |
| October | First frost approaches | Harvest remaining pumpkin; cover plants on frost nights |
| November | — | Dormant season |
| December | — | Dormant season |
Pumpkin Growing Tips for Washington Gardeners
- •For Halloween pumpkins, count back 75–100 days from October 31 — plant between late June and mid-July in most climates.
- •Plant on hills or mounds to warm soil and improve drainage; two plants per hill is plenty.
- •Washington's short growing season means start seeds indoors under grow lights — don't rely on windowsill light which produces leggy, weak seedlings that struggle outdoors.
- •Cover young transplants with floating row covers for the first 2–3 weeks outside. The 3–5°F of protection reduces frost damage risk and accelerates early growth.
- •Rotate pumpkins away from squash, cucumber, and melon beds on a 3-year cycle to break disease cycles.
Companion Planting for Pumpkins in Washington
In Washington's cold climate, planting pumpkin with Corn and Bush Bean helps deter pests and improve soil. Avoid planting near Potato and Summer Squash, which inhibit pumpkin growth through root chemistry or shared pest pressure. See the full pumpkin companion planting guide for the complete list.
Pumpkins Planting Dates by City in Washington
Top cities in Washington — select for city-level frost dates and planting calendars.
Frequently Asked Questions
When should I plant pumpkin in Washington?
In Washington (Zone 4b), start pumpkin seeds indoors around April 16–23 and transplant outdoors around May 14–24 — 1 weeks after the state's average last frost of May 7.
What is the last frost date in Washington?
Washington's average last frost date is May 7 in the state's most common Zone 4b. Frost dates vary by city — higher elevations and northern counties run 1 to 3 weeks later than the state average. See the city list below for city-level frost dates.
Can I grow pumpkin year-round in Washington?
Not year-round — Washington's cold season stops pumpkin production. The pumpkin season runs May 7 to October 1, roughly 21 weeks.
What pumpkin varieties grow best in Washington?
For Washington's Zone 4b, consult a local nursery or extension office for pumpkins variety recommendations.
When do I start pumpkin seeds indoors in Washington?
Start pumpkin seeds indoors in Washington around April 16–23, which is 3 weeks before the state's average last frost of May 7. Use grow lights and keep soil temperatures at 70–75°F for fastest germination.