Planting Guides
When to Plant Kale in Chicago: Complete Guide + Best Varieties for Zone 6a
Chicago, Illinois
USDA Zone 6a
Last Frost: May 10
Last updated: October 30, 2025
Plant kale in Chicago March 15-April 1 for spring harvest or August 1-15 for superior fall crops. Zone 6a's 158-day season is ideal for kale production.
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Quick Answer
Plant kale in Chicago March 15-April 1 for spring harvest or August 1-15 for fall crops. Fall-planted kale tastes superior due to frost sweetening.
TL;DR
Plant kale in Chicago March 15-April 1 for spring harvest or August 1-15 for superior fall crops. Zone 6a's frost dates (May 9 to October 14) provide a 158-day growing season perfect for kale. Fall planting produces the sweetest, most flavorful kale as frost converts starches to sugars. Brassica oleracea 'Winterbor' and Brassica oleracea 'Lacinato' varieties excel in Chicago's climate and can survive winter with protection.
Frequently Asked Questions
When should I plant kale in Chicago for the best harvest?
Plant kale in Chicago August 1-15 for fall harvest or March 15-April 1 for spring crops. Fall planting produces superior flavor because frost converts starches to sugars, making leaves sweeter and more tender. The August planting allows plants to mature before Chicago's first frost around October 14, then continues producing through winter with protection.
What are the best kale varieties for Chicago's Zone 6a climate?
Brassica oleracea 'Winterbor' and Brassica oleracea 'Lacinato' are the top choices for Chicago gardeners. Winterbor handles Chicago's winter conditions exceptionally well and can survive under row covers. Lacinato offers better heat tolerance for spring planting and resists bolting during unexpected May heat waves. Both varieties thrive in our 158-day growing season from May 9 to October 14.
Can kale survive Chicago winters outdoors?
Yes, kale can survive Chicago winters with proper protection. Brassica oleracea 'Winterbor' and Brassica oleracea 'Redbor' are the hardiest varieties, surviving Zone 6a winters under row covers or in cold frames. Apply 4-6 inches (10-15 cm) of straw mulch around plants in late November and use lightweight row covers when temperatures drop below 20°F (-7°C). Many Chicago gardeners harvest fresh kale through January using these techniques.
How do I prevent kale from bolting in Chicago's variable spring weather?
Choose heat-tolerant varieties like Brassica oleracea 'Lacinato'} for spring planting, as it resists bolting better than curly types during Chicago's May heat waves. Plant early (March 15-April 1) to establish plants before summer heat arrives. Provide afternoon shade during unexpected hot spells and maintain consistent soil moisture. If plants start showing signs of bolting (flower buds forming), harvest all leaves immediately—the flower shoots are edible too.
What pests should Chicago kale growers watch for?
Cabbage worms are the primary pest, appearing as white butterflies in spring that lay eggs on leaves. The green caterpillars can quickly defoliate plants. Use row covers to prevent egg-laying or spray Bt (Bacillus thuringiensis) weekly once caterpillars appear. Flea beetles create shot-hole damage on young plants—protect seedlings with row covers until they're established. Aphids cluster on new growth during cool, humid spring weather—control with strong water sprays or neem oil.
How long does it take kale to mature in Chicago?
Most kale varieties mature in 60-75 days from seed to harvest in Chicago's climate. Brassica oleracea 'Red Russian'} is fastest at 50-60 days, while Brassica oleracea 'Winterbor'} takes 60-75 days. However, you can start harvesting baby leaves as early as 30 days after planting. Fall-planted kale grows slower as days shorten but continues producing through winter, giving you months of harvest from a single planting.
Should I start kale indoors or direct sow in Chicago?
Direct sowing works best for Chicago's climate and kale's growing habits. Kale doesn't transplant as well as other brassicas and often performs better when direct sown. For spring crops, direct sow March 15-April 1 when soil can be worked. For fall crops (recommended), direct sow August 1-15. If you prefer transplants, start seeds indoors 6-8 weeks before transplanting but harden off carefully over 7-10 days before planting outside.
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Patricia "Pat" O'Brien
Pat has been gardening in Milwaukee for over thirty years, through every kind of Wisconsin weather. She worked as a school librarian and started gardening seriously when her kids were small—she wanted them to know where food came from. Now retired, she's a certified Master Gardener and runs the plant sale at her local garden club every spring. She specializes in cold-hardy perennials, native wildflower meadows, and the art of getting a vegetable garden producing in Wisconsin's short but intense growing season. Pat is practical and patient—she's seen enough Wisconsin winters to know that gardening here is a long game, and she writes with the steady confidence of someone who's been doing this a long time.
