When To Plant Zucchini In Seattle

The best time to plant zucchini in Seattle is from late May through mid-July, once soil temperatures stay reliably above 60°F and all danger of frost has passed.
 
If you’ve been wondering when to plant zucchini in Seattle, the short answer is to wait until the soil warms up, not just the air.
 
Seattle’s cool, wet springs can trick you into planting too early, and zucchini planted in cold soil will sulk, rot, or refuse to grow at all.
 
In this post, we’ll walk through exactly when to plant zucchini in Seattle, the ideal conditions for a happy crop, and a few Seattle-specific tips for success.
 
Let’s dig in.
 

When to Plant Zucchini in Seattle

When to plant zucchini in Seattle comes down to soil temperature and frost dates, and here’s the breakdown:
 

1. Wait Until Late May or Early June

Seattle sits in USDA zone 8b, which means the last frost typically happens in early to mid-March.
 
But zucchini is a heat lover, and it wants soil that’s at least 60°F before it will grow well.
 
In Seattle, that usually happens around late May or the first week of June.
 
So if you’re asking when to plant zucchini in Seattle, mark late May on your calendar as the safe starting point.
 

2. Watch Soil Temperature, Not the Calendar

The calendar is a guide, but your soil thermometer is the real boss.
 
Zucchini seeds germinate best when soil is between 70°F and 95°F, and they’ll struggle below 60°F.
 
Push a soil thermometer about two inches deep in the morning for a few days in a row.
 
When it holds steady at 60°F or higher, you’re clear to plant zucchini in Seattle.
 

3. Don’t Plant Before the Last Frost

Zucchini seedlings are tender and won’t survive a frost, so timing matters.
 
While Seattle’s official last frost is in March, cool nights can linger into May.
 
If you plant zucchini in Seattle too early, a single cold snap can set you back weeks or kill your plants outright.
 
Better to wait a couple of weeks than to replant.
 

Ideal Conditions for Planting Zucchini in Seattle

Getting the timing right is only half the battle, so here’s what zucchini needs once you plant:
 

1. Full Sun and Warm Soil

Zucchini needs at least six to eight hours of direct sun, which can be a tall order in cloudy Seattle.
 
Pick the sunniest spot in your garden, and consider raised beds that warm up faster than ground soil.
 
You can also lay black plastic over the bed a week or two before planting to give the soil a head start.
 

2. Rich, Well-Draining Soil

Zucchini is a heavy feeder, so work plenty of compost into the soil before you plant zucchini in Seattle.
 
Good drainage matters too, since our wet springs can waterlog roots.
 
Raised beds or mounds work great for keeping roots happy and warm.
 

3. Protection from Cool Nights

Even after you plant zucchini in Seattle, keep an eye on overnight lows.
 
If temps dip below 50°F, cover your plants with a cloche, row cover, or even a bucket.
 
A little protection in early June can make the difference between thriving plants and stunted ones.
 

Second Planting Window for Zucchini in Seattle

Here’s a bonus: you can plant zucchini in Seattle twice in one season.
 

1. Plant Again in Early to Mid-July

If you sow another round of zucchini in Seattle around early to mid-July, you’ll harvest into September and even October.
 
This second planting often dodges the worst of the powdery mildew that hits older plants late in summer.
 

2. Skip Starting Seeds Indoors Too Early

Zucchini grows so fast that indoor seed starting isn’t really necessary here.
 
If you do start seeds inside, do it just two to three weeks before your target planting date.
 
Start them too early and you’ll have leggy seedlings begging to go outside before the soil is ready.
 

So, When to Plant Zucchini in Seattle?

Zucchini should be planted in Seattle from late May through mid-July, once the soil has warmed to at least 60°F and frost risk has passed.
 
Patience is the name of the game with our cool Pacific Northwest springs.
 
Wait for warm soil, pick a sunny spot, protect young plants from chilly nights, and you’ll be swimming in zucchini by midsummer.
 
Now you know exactly when to plant zucchini in Seattle, so go get those seeds ready.