Planting Guides
When to Plant Kale in Seattle: Complete Guide + Best Varieties for Zone 8b
Seattle, Washington
USDA Zone 8b
Last Frost: Mar 15
Last updated: October 30, 2025
Learn when to plant kale in Seattle with specific dates for Zone 8b. Compare 5 varieties, get a complete timeline, and discover which kale grows best in Washington.
— Image © PlantReference.org 2026
Quick Answer
Plant kale year-round in Seattle: March-April for spring harvest, July-September for fall/winter crops. Brassica oleracea 'Lacinato' and Brassica oleracea 'Winterbor' overwinter perfectly in Zone 8b.
TL;DR
Seattle's Zone 8b climate is perfect for year-round kale growing with mild winters and cool summers. Plant Brassica oleracea 'Lacinato' in August for winter harvest, Brassica oleracea 'Winterbor' in September for frost-sweetened leaves, and Brassica oleracea 'Red Russian' in March for spring crops. Seattle's last frost is March 14 and first frost November 14, giving you a 245-day growing season ideal for continuous kale production.
Frequently Asked Questions
When is the best time to plant kale in Seattle for winter harvest?
Plant kale in Seattle between August 15 and September 15 for optimal winter harvest. This timing allows plants to mature before the November 14 first frost date, then slow their growth during winter while continuing to produce harvestable leaves. Brassica oleracea 'Winterbor' and Brassica oleracea 'Lacinato' planted during this window will provide fresh greens throughout Seattle's mild Zone 8b winter. The key is giving plants enough time to establish good size before the shorter days and cooler temperatures of late fall.
Can I grow kale year-round in Seattle?
Yes, Seattle is ideal for year-round kale growing due to its Zone 8b climate with mild winters and cool summers. Plant spring crops in February-March, summer plantings in June-July, and fall/winter crops in August-September. Use Brassica oleracea 'Lacinato' for the most reliable year-round production, as it handles both Seattle's wet winters and dry summers without bolting. During the coldest weeks of January-February, growth slows but plants continue producing leaves. This makes Seattle one of the best climates in the country for continuous kale production.
Which kale varieties work best in Seattle's rainy climate?
Brassica oleracea 'Lacinato'} and Brassica oleracea 'Winterbor'} are top choices for Seattle's wet climate. Brassica oleracea 'Lacinato' has flat leaves that shed water well and resist rot, while Brassica oleracea 'Winterbor' has excellent cold tolerance for overwintering. Avoid Brassica oleracea 'Red Russian'} for winter growing as its tender leaves are more susceptible to moisture-related problems. Brassica oleracea 'Redbor'} works well but needs good drainage due to its ruffled leaves that can hold moisture. Focus on varieties bred for cold, wet conditions rather than heat tolerance.
How do I prevent slugs from destroying my kale in Seattle?
Slugs are the biggest kale pest in Seattle's moist climate. Create physical barriers using copper tape around raised beds, as slugs won't cross copper. Apply iron phosphate-based slug baits (safer than metaldehyde) around plants in evening when slugs are active. Hand-pick slugs at night using a flashlight—they're most active after 10 PM. Improve drainage around plants as slugs thrive in consistently moist soil. Plant Brassica oleracea 'Winterbor'} which has tougher leaves that slugs find less appealing than tender varieties like Brassica oleracea 'Red Russian'}.
When does frost improve kale flavor in Seattle?
Seattle's first frost typically occurs around November 14, which is when kale flavor dramatically improves. The frost triggers the plant to convert starches into sugars as a cold-protection mechanism, making leaves noticeably sweeter and more tender. Brassica oleracea 'Winterbor'} and Brassica oleracea 'Redbor'} show the most dramatic improvement after frost. Plan fall plantings so that kale reaches maturity by mid-November to take advantage of this natural sweetening process. Leaves harvested in December and January after multiple frosts often taste completely different from summer-harvested kale—much sweeter with less bitterness.
How much space do I need to grow kale in Seattle?
Each kale plant needs 12-18 inches (30-45 cm) spacing in Seattle's rich growing conditions. In raised beds, you can fit 4-6 plants per 4x4 foot (1.2x1.2 meter) section. Brassica oleracea 'Vates'} is most compact for small spaces, while Brassica oleracea 'Lacinato'} and Brassica oleracea 'Winterbor'} need fuller spacing. Container growing works excellently in Seattle—use at least 5-gallon (19-liter) containers for mature plants. Seattle's mild climate allows dense plantings since plants don't face heat stress that requires extra spacing for air circulation in hot climates.
Should I start kale from seeds or transplants in Seattle?
Direct seeding works excellently in Seattle due to the mild climate and consistent moisture. Plant seeds ½ inch (1.3 cm) deep from February through September for different harvest seasons. Germination rates are typically 85-90% in Seattle's favorable conditions compared to 60-70% in harsher climates. Transplants give you more control over timing and spacing, especially useful for precise succession planting. Start seeds indoors 4-6 weeks before transplanting. Seattle's mild weather makes hardening off easier than in extreme climates. Both methods work well—choose based on your preference and timing needs.
NEW PLANT DAILY
Think you know your plants?
Test your botanical knowledge with a new plant identification challenge every day. Build your streak, learn fascinating plant facts, and become a plant identification expert!
Build your streak
One chance per day
Learn as you play
Free account required • Takes less than 30 seconds
Tagged with
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.
