When to plant zucchini and summer squash in Spokane, WA

Plant zucchini and summer squash in the garden in Spokane May 20 – Jun 17, either as seeds or as young plants started indoors Apr 22–29.

Easy Plant seeds or young plants

Why these dates

Spokane's typical last spring frost is April 26. 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 20.

Inland Northwest. Higher, colder interior valleys. Cold springs and an earlier fall mean a shorter season; quick-maturing varieties pay off.

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 22–29 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 20 – Jun 17, 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 Spokane, WA?

Typically April 26. In 9 years out of 10, frost is over by May 10. These are 1991–2020 NOAA climate normals for Spokane International Airport.

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

The spring planting window runs through June 17. Later plantings may not have time to produce before the first fall frost, which usually arrives around October 12.

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

April 22 to April 29, which is 4 to 3 weeks before the May 20 planting date. Or buy young plants at a garden center instead.