Planting Guides
When to Plant Squash in Chicago: Complete Guide + Best Varieties for Zone 6a
Chicago, Illinois
USDA Zone 6a
Last Frost: May 10
Last updated: October 30, 2025
Plant squash in Chicago after May 9 when soil warms to 65°F. Zone 6a's 158-day season supports all squash varieties with proper timing and variety selection.
— Image © PlantReference.org 2026
Quick Answer
Plant squash in Chicago after May 9 when soil reaches 65°F. Summer squash direct seed May 23-June 15, winter squash transplants May 23-30.
TL;DR
Plant squash in Chicago after May 9 when soil reaches 65°F and frost danger passes. Summer varieties like Cucurbita pepo 'Black Beauty' mature in 45-60 days, while winter squash needs 80-110 days before October 14 first frost. Start winter varieties indoors April 20-27 for transplanting after May 23.
Frequently Asked Questions
When should I plant squash in Chicago to avoid frost damage?
Plant squash in Chicago after May 23, which provides a 2-week buffer after our May 9 last frost date. Soil temperature should reach 65°F for proper germination. Summer squash can be planted through mid-June, while winter squash needs planting by May 30 to mature before October 14 first frost. Indoor starting in late April gives winter varieties the extra time they need.
Which squash varieties work best in Chicago's Zone 6a climate?
Cucurbita pepo 'Black Beauty'} zucchini and Cucurbita pepo 'Yellow Crookneck'} are reliable summer varieties that mature in 50-55 days. For winter storage, Cucurbita pepo 'Acorn'} (85 days) and Cucurbita pepo 'Delicata'} (85 days) work consistently. Cucurbita moschata 'Butternut'} (95-100 days) requires indoor starting but provides excellent storage. Avoid varieties requiring more than 100 days unless started indoors.
How do I manage large squash vines in small Chicago city lots?
Choose bush varieties like {Cucurbita pepo 'Black Beauty'} that spread only 3-4 feet for small spaces. Train vining types along fences or into lawn areas where sprawling won't damage other plants. Vertical trellising works for smaller winter squash varieties. Plant large vining types like {Cucurbita moschata 'Butternut'} at garden edges where 8-foot spread won't shade other crops.
What's the biggest pest problem for Chicago squash growers?
Squash vine borer represents the most serious threat in Chicago. Adult moths emerge in late June and lay eggs at stem bases. Larvae bore into stems, causing sudden plant collapse. Prevention: Use floating row covers until flowering begins. Early detection: Check weekly for small holes and sawdust-like frass at stem bases starting in July. Treatment: Surgically remove larvae and cover wounds with soil to encourage new roots.
How do I know when winter squash is ready to harvest in Chicago?
Winter squash reaches maturity when stems become dry and corky, skin hardens so fingernail cannot puncture it, and the ground spot turns cream or tan. In Chicago, this typically occurs mid-September through early October before our October 14 first frost. If frost threatens before complete maturity, harvest and use fresh rather than storing. Properly mature squash stores 2-6 months depending on variety.
Can I grow butternut squash successfully in Chicago's climate?
Yes, but {Cucurbita moschata 'Butternut'} requires careful timing in Chicago's 158-day season. Start seeds indoors April 20-27 and transplant after May 23 when soil reaches 65°F. This variety needs 95-100 days to mature, making it marginal for direct seeding. The long vines require 6-8 feet of space, but the excellent storage potential (4-6 months) makes it worthwhile for Chicago gardeners with adequate space.
How often should I water squash plants during Chicago's humid summers?
Apply 1-2 inches of water weekly in one deep soaking rather than frequent shallow watering. This encourages deep root development crucial for Chicago's sometimes variable rainfall. Water at soil level using drip irrigation or soaker hoses to prevent fungal diseases that thrive in our humid climate. Apply 3-4 inch organic mulch layer to conserve moisture and reduce watering needs, keeping mulch 6 inches from stems.
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
P
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.
