🌿 Can I Plant Fennel in Seattle, WA?

2026 planting guide for Zone 8b · Last frost ~March 18 · Growing season ~242 days

⏳ WAIT — Temps borderline — ideal is 60°F+ overnight — tight harvest window

Conditions are above the minimum safe threshold but still below ideal for Fennel. Overnight lows of 60°F+ would give much better results. Note: timing is tight — harvest may run close to the average first fall frost around Nov 10. Consider a fast-maturing variety.

Planting window: Jul 30 – Aug 13 (tight — harvest near frost)
Wait a bit longer. Watch for overnight lows to reliably reach 60°F.
Live result based on current forecast for Seattle, WA · Updates every 6 hours
USDA Zone
8b
Last Spring Frost
~March 18
First Fall Frost
November 15
Growing Season
~242 days
Ideal Temp for Fennel
60–85°F
Frost Risk
✅ Tolerant

Growing Fennel in Seattle

Seattle's Zone 8b maritime climate is notoriously cool and cloudy, which means warm-season crops like tomatoes and peppers need all the help they can get. A south-facing wall or greenhouse extension is almost essential for tomatoes. On the plus side, cool-season crops like kale, lettuce, and peas absolutely thrive in Seattle's mild, moist conditions.

In Seattle (last frost around March 18), aim to direct sow or transplant fennel outside around March — approximately 0 weeks after your last expected frost. Starting seeds indoors 4 weeks before the last frost date gives you a significant head start.

Fennel thrives between 60°F and 85°F. It tolerates temperatures as low as 25°F, making it a candidate for early spring planting before the last frost date. Expect 65–90 days from transplant to first harvest. Direct sow preferred — dislikes root disturbance. Keep away from dill and tomatoes.

Frequently Asked Questions

When can I plant fennel in Seattle, WA?

In Seattle (last frost around March 18), aim to direct sow or transplant fennel outside around March — approximately 0 weeks after your last expected frost. For best results, start seeds indoors 4 weeks before that — giving you strong transplants ready to go out at the right time.

What is the USDA hardiness zone for Seattle?

Seattle, WA is in USDA Plant Hardiness Zone 8b. The last expected spring frost is around March 18, and the first fall frost arrives around November 15. This zone classification helps you understand which perennials survive winter and when annual vegetables can safely go outdoors.

Is it safe to plant fennel outside in Seattle right now?

That depends on the current weather forecast. Fennel needs temperatures above 25°F (ideally 60–85°F) to thrive. CanIPlant checks your real 7-day forecast and any active frost alerts to give you a live YES, NO, or WAIT answer — just enter your ZIP code.

Can I grow fennel in Seattle 2026?

Yes — Fennel grows well in Seattle, WA. With a Zone 8b climate and a growing season of ~242 days, Seattle is well-suited for warm-season crops like fennel. As a frost-tolerant crop, fennel can even go out a few weeks before the last frost date.

Grow Fennel in Other Cities

New York, NYLos Angeles, CAChicago, ILHouston, TXPhoenix, AZPhiladelphia, PASan Antonio, TXSan Diego, CA

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