Seattle, WA Planting Dates — Moon Phase Garden

The four dates that matter

Date	When	What it means
Last spring frost (50%)	Mar 2	Half of all years see a freeze after this date. It is an average, not a guarantee.
Last spring frost (10%)	Mar 23	Only one year in ten freezes after this. Use it for anything you cannot afford to replant.
First fall frost (50%)	Nov 23	Half of all years freeze before this date. Fall crops are counted back from here.
First fall frost (10%)	Nov 6	An early-freeze year. If a crop must finish, aim to harvest before this.

USDA zone 9a 266 frost-free days Elevation 371 ft Station Seattle Tacoma Intl Ap

Spring & summer planting in Seattle

Dates are calculated from this location's own last-frost date, not from a generic zone chart. “Best moon days” are the days inside each window that fall in the crop's traditional phase — the same rule the app uses.

Crop	Start seed indoors	Plant outdoors	Best moon days	Days to harvest
Strawberry (crowns) transplant	—	Jan 1 – Feb 9	Jan 3, Feb 1 Full Moon	perennial — first real harvest next season
Garlic cloves/sets Better planted in fall — see below	—	Jan 14 – Feb 14	Feb 2–7 Waning Gibbous	240–300
Asparagus (crowns) transplant	—	Jan 19 – Feb 23	Jan 25 First Quarter	perennial — first real harvest 2–3 years
Chives either	Jan 5	Jan 19 – Feb 23	Jan 19–24 Waxing Crescent	75–90
Onion (from sets/transplants) cloves/sets	—	Jan 19 – Feb 23	Feb 2–7 Waning Gibbous	90–120
Peas (English/snap) direct sow	—	Jan 19 – Feb 23	Jan 25 First Quarter	55–75
Spinach direct sow	—	Jan 19 – Feb 23	Jan 19–24 Waxing Crescent	35–50
Cabbage transplant	Dec 29	Jan 26 – Feb 23	Feb 18–23 Waxing Crescent	65–90
Collards either	Jan 19	Jan 26 – Mar 16	Feb 18–23 Waxing Crescent	55–85
Kale either	Jan 19	Jan 26 – Mar 2	Feb 18–23 Waxing Crescent	50–65
Lettuce (leaf) either	Jan 26	Jan 26 – Mar 23	Feb 18–23 Waxing Crescent	40–55
Potato cloves/sets	—	Jan 26 – Mar 2	Feb 1 Full Moon	70–120
Radish direct sow	—	Jan 26 – Mar 23	Feb 2–7 Waning Gibbous	22–35
Turnip direct sow	—	Jan 26 – Mar 9	Feb 2–7 Waning Gibbous	40–60
Broccoli transplant	Dec 29	Jan 31 – Mar 2	Feb 18–23 Waxing Crescent	55–80
Brussels Sprouts transplant	Dec 29	Jan 31 – Mar 2	Feb 18–23 Waxing Crescent	90–110
Leek transplant	Dec 22	Jan 31 – Mar 2	Feb 2–7 Waning Gibbous	100–120
Lettuce (head) transplant	Jan 12	Jan 31 – Mar 2	Feb 18–23 Waxing Crescent	60–85
Parsley either	Dec 29	Jan 31 – Mar 9	Feb 18–23 Waxing Crescent	70–90
Parsnip direct sow	—	Jan 31 – Mar 9	Feb 1, Mar 3 Full Moon	100–150
Shallot cloves/sets Better planted in fall — see below	—	Jan 31 – Mar 2	Feb 2–7 Waning Gibbous	90–120
Beet direct sow	—	Feb 2 – Mar 23	Mar 3 Full Moon	50–65
Kohlrabi either	Jan 19	Feb 2 – Mar 9	Feb 18–23 Waxing Crescent	45–60
Carrot direct sow	—	Feb 9 – Mar 23	Mar 3 Full Moon	65–85
Cauliflower transplant	Dec 29	Feb 9 – Mar 2	Feb 18–23 Waxing Crescent	55–80
Cilantro direct sow	—	Feb 9 – Mar 23	Feb 18–23 Waxing Crescent	45–70
Swiss Chard direct sow	—	Feb 9 – Apr 1	Feb 18–23 Waxing Crescent	50–60
Dill direct sow	—	Feb 16 – Apr 1	Feb 18–23 Waxing Crescent	40–60
Cucumber either	Feb 9	Mar 2 – Apr 1	Mar 25 First Quarter	50–70
Green Beans (bush) direct sow	—	Mar 2 – Apr 16	Mar 25 First Quarter	50–65
Oregano transplant	Jan 5	Mar 2 – Mar 23	— First Quarter	cut as needed
Sage transplant	Jan 5	Mar 2 – Mar 23	— First Quarter	cut as needed
Sweet Corn direct sow	—	Mar 2 – Apr 16	Mar 25 First Quarter	60–100
Thyme transplant	Jan 5	Mar 2 – Mar 23	— First Quarter	cut as needed
Zucchini / Summer Squash either	Feb 9	Mar 2 – Apr 1	Mar 25 First Quarter	45–60
Basil either	Jan 19	Mar 9 – Apr 1	Mar 19–24 Waxing Crescent	30–60
Dry Beans direct sow	—	Mar 9 – Apr 6	Mar 25 First Quarter	85–100
Pole Beans direct sow	—	Mar 9 – Apr 11	Mar 25 First Quarter	60–75
Pumpkin direct sow	Feb 9	Mar 9 – Apr 6	Mar 25 First Quarter	90–120
Rosemary transplant	Mar 2	Mar 9 – Apr 1	Mar 25 First Quarter	cut as needed
Tomatillo transplant	Jan 19	Mar 9 – Apr 1	Mar 25 First Quarter	60–75
Tomato transplant	Jan 19	Mar 9 – Apr 1	Mar 25 First Quarter	60–85
Winter Squash direct sow	Feb 9	Mar 9 – Apr 6	Mar 25 First Quarter	85–110
Cantaloupe / Muskmelon either	Feb 9	Mar 16 – Apr 6	Mar 25 First Quarter	75–90
Eggplant transplant	Jan 5	Mar 16 – Apr 6	Mar 25 First Quarter	60–90
Okra direct sow	Feb 2	Mar 16 – Apr 11	Mar 25 First Quarter	50–70
Pepper transplant	Jan 5	Mar 16 – Apr 6	Mar 25 First Quarter	60–90
Sweet Potato slips	—	Mar 16 – Apr 11	Apr 2–7 Waning Gibbous	90–150
Watermelon either	Feb 9	Mar 16 – Apr 6	Mar 25 First Quarter	70–90

Fall planting in Seattle

Fall dates count backward from the first frost, and they add time back for the “fall factor” — days are shortening and cooling, so a crop grows slower than the seed packet promises. Sowing late is the single most common way a fall garden fails.

Crop	Sow or set out	Best moon days	Days to harvest	Hardiness
Tomato	Jul 8 – Aug 13	Jul 21	60–85	very tender
Brussels Sprouts	Jul 11 – Jul 28	Jul 15–20	90–110	hardy
Potato	Jul 16 – Aug 17	Jul 29	70–120	semi-hardy
Sweet Corn	Jul 21 – Aug 13	Jul 21	60–100	tender
Pole Beans	Jul 31 – Aug 13	—	60–75	tender
Parsley	Aug 3 – Aug 17	Aug 13–17	70–90	semi-hardy
Okra	Aug 5 – Sep 4	Aug 19	50–70	very tender
Cabbage	Aug 10 – Aug 22	Aug 13–18	65–90	hardy
Carrot	Aug 10 – Aug 22	—	65–85	semi-hardy
Collards	Aug 10 – Sep 1	Aug 13–18	55–85	hardy
Cucumber	Aug 10 – Aug 23	Aug 19	50–70	tender
Broccoli	Aug 15 – Sep 1	Aug 15–18	55–80	hardy
Cauliflower	Aug 15 – Sep 1	Aug 15–18	55–80	semi-hardy
Green Beans (bush)	Aug 15 – Aug 23	Aug 19	50–65	tender
Lettuce (head)	Aug 15 – Aug 27	Aug 15–18	60–85	semi-hardy
Peas (English/snap)	Aug 15 – Sep 1	Aug 19	55–75	hardy
Beet	Aug 20 – Sep 6	Aug 27	50–65	semi-hardy
Kale	Aug 20 – Sep 6	—	50–65	hardy
Swiss Chard	Aug 20 – Sep 6	—	50–60	semi-hardy
Zucchini / Summer Squash	Aug 20 – Aug 28	—	45–60	tender
Basil	Aug 25 – Sep 12	Sep 11–12	30–60	very tender
Kohlrabi	Aug 25 – Sep 11	Sep 11	45–60	hardy
Cilantro	Aug 30 – Sep 11	Sep 11	45–70	semi-hardy
Lettuce (leaf)	Aug 30 – Sep 16	Sep 11–16	40–55	semi-hardy
Turnip	Aug 30 – Sep 16	Aug 30–Sep 3	40–60	hardy
Spinach	Sep 4 – Sep 21	Sep 11–16	35–50	hardy
Dill	Sep 9 – Sep 16	Sep 11–16	40–60	semi-hardy
Radish	Sep 9 – Oct 4	Sep 27–Oct 2	22–35	hardy
Garlic	Oct 24 – Dec 14	Oct 26–31	240–300	hardy
Shallot	Nov 7 – Dec 8	Nov 25–29	90–120	hardy

Bottom line: the 50% frost date is a coin flip, not a green light. If you would be sick about losing a flat of tomatoes, plant to the Mar 23 date instead and keep a row cover handy either way.

Where these numbers come from

The frost dates on this page are observed station normals, not estimates: they come from Seattle Tacoma Intl Ap (GHCN USW00024233), one of 6,808 U.S. stations in NOAA's 1991–2020 Climate Normals. The hardiness zone is from the 2023 USDA Plant Hardiness Zone Map. Crop timing is expressed as offsets from your frost dates, drawn from university Extension planting guides.

How precise is any of this?

Extension recommendations for the same crop routinely disagree by two to four weeks, and occasionally more, so these offsets should be presented as windows and starting points rather than deadlines. Three things drive the spread. (1) Regional risk tolerance: for warm-season crops, Colorado State and Utah State put tomatoes, peppers and melons out about 14 days after the last frost, while University of Missouri's calendar works out to roughly 25-35 days after the last frost and University of Maryland's window runs from the frost date itself out to 45 days past it. That is a real 6-week spread for the single most popular garden crop, and it exists because a short-season mountain state is optimizing against a short season while a humid continental state is optimizing against cold, wet spring soil. (2) Soil temperature versus calendar date: most Extension services now say the honest trigger is soil temperature at 4 inches, not the frost date, and the frost-relative number is a convenience translation. A cold, wet spring can push the real date two or three weeks past the calendar recommendation. (3) Days-to-maturity is variety-specific and is measured differently for direct-seeded versus transplanted crops - seed catalogs count from transplant date for tomatoes, peppers, eggplant and cole crops, but from sowing for roots and greens - so a 'days to maturity' range of 60-85 for tomato is genuinely 60-85 depending on which packet you bought. Additionally, the average last frost is a 50% probability, meaning half of all years have a frost after that date; Extension services commonly advise waiting 1-2 weeks past it for anything frost-tender, or being prepared to cover. Treat every number here as plus or minus about 10-14 days.

On the station itself: a weather station is one point. Cities hold their heat, valleys pool cold air, and a garden on a north slope can run two weeks behind one a mile away. Treat this page as your starting point and let your own garden correct it — that is exactly what the journal in the app is for.

Nearby locations

Renton, WA zone 8b Kent, WA zone 8b Federal Way, WA zone 8b Bellevue, WA zone 9a Tacoma, WA zone 8b Kirkland, WA zone 9a

Want this on your phone, in your garden? Moon Phase Garden keeps your frost dates, your planting windows and tonight's moon phase in one place, works offline, and lets you override these dates with what your own garden actually does. Free and ad-free.

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