When to Plant Squash in Oregon
Published: April 21, 2026
Oregon gardeners in Zone 4b have a 21-week frost-free window for squash (May 7 to October 1). Warm-season crops like squash must be started indoors early to maximize the short window — Oregon's late spring and early fall frost dates leave little room for error. This guide gives exact dates for Oregon based on your local frost calendar.
Squash Planting Dates for Oregon
| 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 | June 28 – July 18 |
| Fall crop start | July 23–August 2 |
| Fall harvest | September 6 |
| First fall frost (average) | October 1 |
Dates above assume Zone 4b, the most common zone in Oregon. Gardeners in cooler Portland (Zone 4b) plant 1–2 weeks later; warmer Medford (Zone 5b) can plant 1–2 weeks earlier.
Growing Squash in Oregon's Climate
Oregon's cold Zone 4b climate puts warm-season squash 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 Oregon. 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 squash needs for aggressive root growth.
Common squash pests to watch for in Oregon include Squash Vine Borer and Squash Bug. The first line of defense is companion planting: Corn and Bush Beans 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.
Squash Garden Calendar for Oregon
| 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 65°F+; nighttime lows above 50°F |
| June | Peak growth; water 1 inch/week | Monitor for pests daily; stake or support as needed |
| July | Start fall crop seeds | Fall transplants go in 10 weeks before first frost |
| August | — | Dormant season |
| September | — | Dormant season |
| October | First frost approaches | Harvest remaining squash; cover plants on frost nights |
| November | — | Dormant season |
| December | — | Dormant season |
Squash Growing Tips for Oregon Gardeners
- •Plant only after soil is fully warm (65°F+) — cold soil rots seeds and creates disease-prone seedlings.
- •Squash vine borer kills plants from the inside in July–August in the eastern US; plant a backup crop in early July.
- •Oregon'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.
- •Hand-pollinate using a small brush if fruit falls off small — squash need bee visits for fruit set.
Companion Planting for Squash in Oregon
In Oregon's cold climate, planting squash with Corn and Bush Beans helps deter pests and improve soil. Avoid planting near Potato and Fennel, which inhibit squash growth through root chemistry or shared pest pressure. See the full squash companion planting guide for the complete list.
Squash Planting Dates by City in Oregon
Top cities in Oregon — select for city-level frost dates and planting calendars.
Frequently Asked Questions
When should I plant squash in Oregon?
In Oregon (Zone 4b), start squash 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 Oregon?
Oregon'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 squash year-round in Oregon?
Not year-round — Oregon's cold season stops squash production. The squash season runs May 7 to October 1, roughly 21 weeks. A fall crop extends harvest into late autumn.
What squash varieties grow best in Oregon?
For Oregon's Zone 4b, Raven and Early Prolific Straightneck set fruit quickly — important in short seasons.
When do I start squash seeds indoors in Oregon?
Start squash seeds indoors in Oregon 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.