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Collard greens
Habit (mature) · Kaweesaesther / Wikimedia Commons · CC BY-SA 4.0
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Collard greens
Brassica oleracea (Acephala Group)
A cool-weather leafy cabbage relative grown for its broad, leathery, blue-green leaves that grow in a loose upright rosette on a thick stem — never forming a head ("acephala" is Greek for headless). A biennial almost always grown as an annual, it sweetens after a fall frost and, in mild-winter regions, keeps producing leaves through winter until it bolts in spring. One of the most cold-tolerant vegetables in the cabbage family.
Review: Source-backed
Climate fit: moderate (63/100)
Edible
Container
Light
Full sun
Water
Moderate water
Mature size
12-72" tall · 18" apart
Hardy in zones
2a-11b
brutally cold to nearly frost-free winters
Summer heat range
Cool-Warm
cool to warm summers Interim Plotwright tier until the plant AHS range is authored.
Native in Illinois
No
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Collards are among the most cold-hardy cabbage-family vegetables, but they are a cool-season crop: heat tolerance is limited, so summer culture in hot regions needs afternoon shade per Missouri Botanical Garden PlantFinder.
Climate notes
Cold hardiness
Now
Zone 6b
USDA
Chicago, IL · 1991-2020 average annual coldest day
Source: USDA Plant Hardiness Zone Map 2023 (1991-2020 climatology) via ArcGIS FeatureServer
Well-suited
2050
Zone 7b
Plotwright
Your zone + climate-model shift · SSP3-7.0 (regional rivalry)
Well-suited
In plain terms: cold winters — coldest nights typically around -3°F.
Well-suited today and still thriving in 2050.
Heat tolerance
Loading current AHS heat-zone and plant heat-fit data at your coordinates…
Sources & citations
Cite this page
For lesson plans, articles, or research that uses this page. To cite a single upstream fact instead, use its specific source listed below.
Plotwright. (2026, May 17). Collard greens (Brassica oleracea (Acephala Group)). Retrieved 2026, June 5, from https://plotwright.garden/plants/collard-greens
Sources for every fact
Every fact on this page traces to a source. 18 fields cited18 source-backed.
Missouri Botanical Garden PlantFinder
Botanical research database
Backs 17 fields
Identity
Summary
Plant type
Light
Moisture
Hardiness
Heat zone
Size
Spacing
Habit
Design roles
Seasonal interest
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Wikimedia Commons
Photo · CC BY-SA 4.0
Backs 1 field
Image
NC State Extension Gardener Plant Toolbox
University extension service
Community photos
The photos above are our reviewed reference set, curated for accuracy.
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