When to plant zucchini and summer squash in Portland, OR

Plant zucchini and summer squash in the garden in Portland May 10 – Jun 7, either as seeds or as young plants started indoors Apr 12–19.

Easy Plant seeds or young plants

Why these dates

Portland's typical last spring frost is March 13. Frost kills zucchini and summer squash, and warm-season crops also need warm soil. Soil here stays cold for weeks after the last frost, so planting waits until about May 10.

West-side valleys. The Willamette Valley, Puget Sound and southern Oregon valleys. Long frost-free seasons, but soil stays cold and wet into May, so warm crops wait for warm soil, not just the last frost.

Difficulty: Easy
Sun: Full sun
Spacing: 3 feet apart
Planting depth: 1 inch deep
Frost: Killed by frost
First harvest: About 55 days after planting

Step by step

Start seeds indoors Apr 12–19 in trays or small pots under a grow light or in your sunniest window. Or skip this step and buy young plants (starts) at a garden center.
Harden off the young plants: about a week before planting, set them outside for a few hours a day, a little longer each day.
Plant them in the garden May 10 – Jun 7, 3 feet apart. If you plant seeds instead, sow them 1 inch deep.
Water deeply once or twice a week rather than a little every day, and mulch once the soil is warm.
Harvest: Pick zucchini at 6 to 8 inches. Miss a few days and you'll have a baseball bat.

Varieties that do well here

Black Beauty
Costata Romanesco
Early Prolific Straightneck

Watch out for

Powdery mildew late in the season. Remove the worst leaves and keep watering at the base.

Two plants feed most families. Pick fruit small and often.

Common questions

When is the last frost in Portland, OR?

Typically March 13. In 9 years out of 10, frost is over by April 1. These are 1991–2020 NOAA climate normals for Portland International Airport.

Is it too late to plant zucchini and summer squash in Portland?

The spring planting window runs through June 7. Later plantings may not have time to produce before the first fall frost, which usually arrives around November 19.

When should I start zucchini and summer squash from seed indoors in Portland?

April 12 to April 19, which is 4 to 3 weeks before the May 10 planting date. Or buy young plants at a garden center instead.