Planting Guides
When to Plant Carrots in Seattle: Zone 8b Dates + Best Varieties
Seattle, Washington
USDA Zone 8b
Last Frost: Mar 15
Last updated: October 30, 2025
Plant carrots in Seattle from February through March for spring harvest. Sow again September through October for overwintered roots in Zone 8b's 245-day growing season.
— Image © PlantReference.org 2026
Quick Answer
Sow carrot seeds outdoors February through March in Seattle. Plant again September through October for overwintered harvest in Zone 8b's mild climate.
TL;DR
Seattle's Zone 8b maritime climate delivers a 245-day growing season between the March 15 last frost and November 15 first frost, with mild winters that support overwintering. Sow spring carrots February through March and plant a fall/winter crop September through October for the sweetest harvest of the year. Daucus carota subsp. sativus 'Nantes' thrives in Seattle's loamy soils, while Daucus carota subsp. sativus 'Napoli' excels as an overwintering variety that produces candy-sweet roots by early spring.
Frequently Asked Questions
When should I start planting carrots in Seattle?
Start sowing carrot seeds outdoors in mid-February if the soil is workable. Seattle's Zone 8b winters are mild enough that February soil temperatures often reach the 40°F (4°C) minimum carrots need for germination. Continue succession sowings every two to three weeks through late March for staggered spring harvests.
Can I grow carrots year-round in Seattle?
Nearly. Seattle's mild Zone 8b climate supports carrot production across three seasons. Spring-sown carrots (February-March) harvest in May-June. Fall-sown carrots (September-October) overwinter and harvest December through March. The only gap is midsummer—July and August—when dry conditions and warmer soil temperatures make germination difficult and existing roots can develop bitterness.
What is the best carrot variety for Seattle?
Daucus carota subsp. sativus 'Nantes' is the top all-around choice for Seattle gardens. The sweet, nearly coreless roots thrive in our sandy loam soils, and the cultivar 'Napoli' is specifically bred for overwintering—it holds in the ground through mild PNW winters without splitting or turning pithy.
How do I protect carrots from slugs in Seattle?
Slug management starts at planting. Scatter iron phosphate bait (brands like Sluggo are safe for pets and wildlife) around the bed when you sow seeds and reapply after heavy rain. This is non-negotiable in Seattle—slugs will destroy an entire planting of carrot seedlings in a single wet night during the vulnerable first three weeks after germination.
How do I overwinter carrots in Seattle?
Sow seeds in September through mid-October. Let the roots grow through autumn until soil temperatures drop below 40°F (4°C), triggering starch-to-sugar conversion that sweetens the roots. In late November, apply 3-4 inches (8-10 cm) of straw or leaf mulch to insulate against occasional hard freezes.
What causes carrot rust fly damage and how do I prevent it?
The carrot rust fly is a small, shiny black fly that lays eggs at the carrot crown. Larvae tunnel into the root, leaving rust-colored channels. Adults emerge in May (first generation) and August (second generation) in the Pacific Northwest.
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Written By
M
Mike Thompson
Mike's been designing residential landscapes in the Seattle area, with a particular focus on Pacific Northwest natives and sustainable practices. He's a Washington State Master Gardener and worked in construction before landscaping, which gives him a practical edge when it comes to building raised beds and hardscaping projects. He runs a small side business propagating and selling unusual perennials at farmers markets on weekends. His property serves as a testing ground for low-maintenance, wildlife-friendly garden designs. Mike's philosophy: if it requires weekly maintenance, it's not sustainable.
