Washington · zones 6b–9a
When to plant zucchini in Washington.
Sow between Apr 21 to Aug 4 in a typical year, keyed to Washington's median last frost around Apr 14. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Zucchini dates for a typical Washington season.
Direct sow
Apr 21 to Aug 4
Keyed to the ~Apr 14 last frost. Sow 1" deep, 24" apart.
Harvest
~50 days later
~8 lb per plant over ~5 weeks.
Washington spans more than one climate: Zone 8 is the most common zone, but the state runs 6b to 9a. That's why the planner works from your ZIP code's frost dates, not your zone: mountain and coastal gardens in the same state can be three weeks apart.
Washington growing notes
Zucchini pollination depends on which side of the state grows it.
Cool, damp mornings shut bees down on the west side
Zucchini depends entirely on bees moving pollen from male flowers to female ones, and Puget Sound's characteristically cool, damp mornings keep bees inactive later into the day than the drier Columbia Basin does, which can leave female flowers open and unpollinated by the time bee activity finally picks up in the afternoon. A female flower that never gets visited simply yellows and drops rather than swelling into fruit, even on an otherwise healthy, vigorous vine.
Hand pollination solves the problem directly: pick a freshly opened male flower, strip the petals back, and touch the pollen-covered center to the center of an open female flower, identifiable by the tiny zucchini already visible behind the bloom. Doing this once a day during any stretch of cool, overcast west-side weather, rather than assuming bees will eventually handle it, keeps a vine setting fruit through conditions that would otherwise cost most of a week's flowers.
Wet leaves invite the fungus, dry heat invites the squash bug
Powdery mildew, the pale dusty coating that spreads across zucchini leaves late in the season, builds fastest in the cool, humid air common near Puget Sound from late summer on, and full spacing between plants, rather than a crowded planting, is the cheapest defense since it keeps air moving through leaves that would otherwise stay damp long after morning dew burns off elsewhere in the garden. East-side heat and low humidity keep mildew from building the same way.
Squash bugs are the pest actually worth a weekly check on Washington zucchini, clustering on the undersides of leaves and moving through a Basin planting faster in the heat than through a cooler Puget Sound row. Set a flat shingle beside the stem in early evening and turn it over first thing the next morning, since the bugs tuck underneath it overnight and a single flip nets several at once. Scraping the copper-bronze egg clusters off leaf undersides before they hatch prevents more damage than anything sprayed once nymphs have already scattered.
Five rounds and a fruit that punishes waiting
Washington's season supports roughly 5 rounds of zucchini sown a few weeks apart, more comfortably on the milder, longer west-side season than a shorter inland window allows, spreading a normally overwhelming harvest into steadier, more manageable batches instead of one flood of squash. Cucumber beetles turn up on zucchini too, feeding on blossoms and scarring young fruit skin; checking blossoms in the cool of early morning, when beetles are still sluggish and easier to catch by hand, works better than a check made once the day has warmed.
Pick zucchini at 6 to 8 inches long rather than letting any fruit size up past that on the vine, since one overgrown zucchini left in place signals the whole plant to slow down setting new fruit, reading the mature fruit as a finished job. Checking vines daily during peak summer growth, rather than every few days, is the only way to catch fruit at that size before it balloons overnight the way this crop is known to.
In Washington: watch for
The pests that find zucchini here.
A middle-length season, about 187 frost-free days, means squash, summer overlaps squash bugs for a stretch each summer. Check plants every week or two and treat early.
Gray shield bugs; leaves wilt and get crispy patches.
Organic fix: Lay a board out overnight and collect them at dawn; scrape bronze egg clusters off leaf undersides.
Yellow striped or spotted beetles chewing leaves and blossoms.
Organic fix: Row cover until the first female flowers open, then hand-pick.
White powder coating the leaves late in the season.
Organic fix: Space for airflow, water the soil rather than the leaves, use resistant varieties.
Your season math: Washington gives zucchini about 187 frost-free days, and it needs roughly 50 days to a first harvest. That fits about 5 re-sown rounds across the season, so you can keep it coming instead of picking once.
Planting zucchini in Washington: questions
When should I plant zucchini in Washington?+
In a typical Washington year, sow zucchini between Apr 21 to Aug 4, keyed to the state's median last frost around Apr 14. Your exact dates shift with your ZIP code and microclimate.
What USDA zone is Washington?+
Washington spans zones 6b–9a, mostly zone 8. But frost dates, not zones, set planting time. The free planner uses your ZIP code's actual frost dates.
How many zucchini plants do I need?+
Depends who you're feeding. The crop page has exact counts per household size, or the free planner does the math for your family in about 60 seconds.