Practical planning tools for short growing seasons.

Seattle, Washington Garden Guide: Planting Dates, Frost Dates and Growing Season

In Seattle, gardeners usually see the last spring frost around March 13 and the first fall frost around November 17, leaving about 249 frost-free days in a typical year. That gives gardeners more room for long-season crops, succession planting, and later sowings.

Growing Season Snapshot

Seattle’s gardening strength comes more from a long moderate shoulder season than from hard summer heat. Many crops enjoy the city’s softness, but heat-demanding plants often need the warmest microclimates available rather than assuming the regional reputation for mildness will be enough.

Typical last spring frost March 13
Typical first fall frost November 17
Typical frost-free days 249
GDD left on May 15 (base 50) 2124

These season boundaries are climate normals, not a forecast. A 50% frost date means a 32°F frost arrives by that date in about half of years — and later in about half. Treat these dates as planning anchors, not guarantees.

Seattle Planting Calendar

A practical guide to when planting usually works in Seattle. These windows are based on climate normals (not a forecast) and line up with the 50% last spring frost and typical early-season heat.

Crop Planting Window Method Best Variety Local Fit
Cool-season / early window Cold-tolerant crops that usually handle cooler spring conditions better.
Peas February 13 – February 27 direct sow Little Marvel Excellent fit
Spinach February 13 – February 27 direct sow Space Excellent fit
Kale February 17 – March 9 direct sow / transplant Winterbor Excellent fit
Beets February 20 – March 6 direct sow Detroit Dark Red Excellent fit
Carrots February 20 – March 6 direct sow Bolero Excellent fit
Lettuce February 20 – March 6 direct sow / transplant Buttercrunch Excellent fit
Onions February 20 – March 6 sets / transplants Redwing Excellent fit
Strawberries February 20 – March 6 plant crowns / transplants Seascape Excellent fit
Swiss Chard February 21 – March 13 direct sow / transplant Bright Lights Excellent fit
Broccoli February 27 – March 13 transplant Packman Excellent fit
Cabbage February 27 – March 13 transplant Stonehead Excellent fit
Cauliflower February 27 – March 13 transplant Snow Crown Excellent fit
Potatoes February 27 – March 13 plant seed potatoes Kennebec Excellent fit
Main warm-season window Crops that usually do best once frost risk fades and the season starts opening up more fully.
Beans March 13 – March 27 direct sow Contender Excellent fit
Sweet Corn March 18 – March 28 direct sow Bodacious Excellent fit
Basil March 22 – April 1 direct sow / transplant Thai Basil Excellent fit
Cucumbers March 22 – April 1 direct sow / transplant Marketmore 76 Excellent fit
Melons March 22 – April 1 direct sow / transplant Athena Excellent fit
Tomatoes March 22 – April 1 transplant Celebrity Excellent fit
Zucchini March 22 – April 1 direct sow / transplant Black Beauty Excellent fit
Pumpkin March 22 – April 1 direct sow / transplant Howden Strong fit
Watermelons March 22 – April 1 direct sow / transplant Crimson Sweet Strong fit
Winter Squash March 22 – April 1 direct sow / transplant Honey Nut Strong fit
Peppers March 29 – April 8 transplant California Wonder Strong fit

How to use this: aim for the earlier part of each window for the most reliable results. Later planting can still work, but it usually depends more on variety maturity, warmer microclimates, and simple protection like row cover or low tunnels.

Common Timing Mistakes

These patterns show up again and again in Seattle — especially in typical years.

  • Planting everything at once instead of staggering crops across the season.
  • Relying on calendar dates instead of crop maturity and typical frost timing.

Missed Your Planting Window? What Can You Still Grow?

This table shows what can still mature from several later-season planting dates in Seattle. It compares the growing degree days still typically available after each checkpoint with the heat each crop usually needs to finish, then applies a 15% safety margin to separate crops that usually still fit from ones that are more borderline.

Usually fits Borderline Too tight
Crop Heat Units May 15 Jun 1 Jul 1 Aug 1
Spinach 450 (base 40) ✅ ✅ ✅ ✅
Lettuce 500 (base 40) ✅ ✅ ✅ ✅
Strawberry 600 (base 40) ✅ ✅ ✅ ✅
Pea 600 (base 40) ✅ ✅ ✅ ✅
Beet 650 (base 40) ✅ ✅ ✅ ✅
Basil 700 (base 50) ✅ ✅ ✅ ✅
Kale 700 (base 40) ✅ ✅ ✅ ✅
Zucchini 750 (base 50) ✅ ✅ ✅ ✅
Carrot 750 (base 40) ✅ ✅ ✅ ✅
Swiss chard 750 (base 40) ✅ ✅ ✅ ✅
Cucumber 800 (base 50) ✅ ✅ ✅ ✅
Broccoli 900 (base 40) ✅ ✅ ✅ ✅
Bean 900 (base 50) ✅ ✅ ✅ ⚠️
Cabbage 1000 (base 40) ✅ ✅ ✅ ✅
Cauliflower 1000 (base 40) ✅ ✅ ✅ ✅
Sweet corn 1100 (base 50) ✅ ✅ ✅ ❌
Potato 1100 (base 45) ✅ ✅ ✅ ✅
Melon 1200 (base 50) ✅ ✅ ✅ ❌
Tomato 1200 (base 50) ✅ ✅ ✅ ❌
Pepper 1300 (base 50) ✅ ✅ ✅ ❌
Onion 1300 (base 45) ✅ ✅ ✅ ✅
Winter squash 1300 (base 50) ✅ ✅ ✅ ❌
Pumpkin 1300 (base 50) ✅ ✅ ✅ ❌
Watermelon 1350 (base 50) ✅ ✅ ✅ ❌

Climate normals GDD planning

Compare your season’s typical heat accumulation against crop requirements before first fall frost.

Heat matters more than calendar days Use this when crop maturity depends on warmth, not just frost-free days. Especially useful for warm-season crops and short-season locations.
Best for borderline crops Especially useful for warm-season crops and short-season locations.

Check Crop Maturity and Timing in Seattle

Enter a ZIP / Postal Code in Seattle and your planting date to see whether different crops can typically mature before first fall frost.

Select one or more crops.

Results

How the Growing Season Works in Seattle

Seattle usually has a relatively forgiving season, but results still depend on how quickly gardens warm in spring and how well crop choices match local conditions.

  • Stagger planting dates: spreading sowings and transplanting windows often works better than planting everything at once.
  • Fall planting is more realistic: many areas still have enough runway for a meaningful second round of faster crops.
  • Summer management becomes the limiter: water, fertility, and pest pressure often matter more than season length alone.

Late-summer note: there is often still meaningful heat left around early August, so second plantings of faster crops can still be worthwhile.

Remaining Season Heat in Seattle (Base 50 GDD)

Growing Degree Days (Base 50°F) measure heat accumulation. “Remaining GDD” shows how much usable heat is typically still available from a given date onward in a normal season.

Planting date Base Typical GDD still available
May 15 50 2124
June 1 50 1967
July 1 50 1589
August 1 50 1049

Use these values to judge whether a crop or variety still has enough heat left after planting. This is especially helpful for later sowings, shorter-maturity choices, and deciding whether a second round is realistic.

How Gardeners Adapt

Experienced gardeners in Seattle usually adjust their timing and crop choices to match how the season actually behaves, not just the calendar.

  • Using row cover or low tunnels to smooth out temperature swings early and late in the season.
  • Succession planting fast crops to keep beds productive through summer.
  • Watching local conditions closely and adjusting timing year by year.

Seattle Garden Planning Chart

A practical “typical year” for planning. Use it as a baseline, then adjust for microclimates and variety maturity.

Stage What it usually means
Early season Start cold-tolerant crops, prep beds, and pay more attention to soil warmth and night temperatures than to the calendar alone.
Main planting Around March 13, the main planting push usually begins as frost risk fades. Warm-season crops generally perform best when they get established promptly.
Peak growth This is when water, fertility, spacing, and pest pressure have the biggest effect on final yield.
Late-summer decisions There is often enough late-season heat left for a meaningful second round of quick crops.
Finish window Plan to have frost-sensitive crops mostly wrapped up by November 17. Cooling nights often slow crops before the first real frost arrives.

Typical season length: 249 frost-free days between the median spring and fall frost dates.

Crop Guides for Seattle

Published crop-specific planting guides for Seattle, ordered from best fit to highest risk.

Excellent fit

Basil

Basil is usually one of the easier crops to grow here.

When to Plant Basil in Seattle

Beans

Seattle usually gives beans enough season that maturity is rarely the hard part.

When to Plant Beans in Seattle

Beets

Beets perform easily here in a typical year.

When to Plant Beets in Seattle

Broccoli

This crop usually has enough season here that maturity is rarely the hard part.

When to Plant Broccoli in Seattle

Cabbage

Very early to late varieties usually fit comfortably here.

When to Plant Cabbage in Seattle

Carrots

Carrots are usually one of the easier crops to grow here.

When to Plant Carrots in Seattle

Cauliflower

Seattle usually gives cauliflower enough season that maturity is rarely the hard part.

When to Plant Cauliflower in Seattle

Cucumbers

Cucumbers perform easily here in a typical year.

When to Plant Cucumbers in Seattle

Kale

This crop usually has enough season here that maturity is rarely the hard part.

When to Plant Kale in Seattle

Lettuce

Very early to mid-season varieties usually fit comfortably here.

When to Plant Lettuce in Seattle

Melons

Melons are usually one of the easier crops to grow here.

When to Plant Melons in Seattle

Onions

Seattle usually gives onions enough season that maturity is rarely the hard part.

When to Plant Onions in Seattle

Peas

Peas perform easily here in a typical year.

When to Plant Peas in Seattle

Potatoes

This crop usually has enough season here that maturity is rarely the hard part.

When to Plant Potatoes in Seattle

Spinach

Very early and early varieties usually fit comfortably here.

When to Plant Spinach in Seattle

Strawberries

Strawberries are usually one of the easier crops to grow here.

When to Plant Strawberries in Seattle

Sweet Corn

Seattle usually gives sweet corn enough season that maturity is rarely the hard part.

When to Plant Sweet Corn in Seattle

Swiss Chard

Swiss chard performs easily here in a typical year.

When to Plant Swiss Chard in Seattle

Tomatoes

This crop usually has enough season here that maturity is rarely the hard part.

When to Plant Tomatoes in Seattle

Zucchini

Very early to late varieties usually fit comfortably here.

When to Plant Zucchini in Seattle

Strong fit

Peppers

Peppers are usually a dependable crop choice here.

When to Plant Peppers in Seattle

Pumpkin

Seattle usually gives pumpkin enough season for reliable maturity.

When to Plant Pumpkin in Seattle

Watermelons

Watermelons perform well here when planted on time.

When to Plant Watermelons in Seattle

Winter Squash

This crop usually gives gardeners some real room to work with.

When to Plant Winter Squash in Seattle

Looking for broader guidance? See planting timing across Washington