Growing Kale: Variety Guide, Timing & Harvest Tips

Q: What is the difference between kale and collard greens?

Both are Brassica oleracea var. acephala . Per NC State Extension, collard greens have large, smooth, flat leaves and are more heat-tolerant than kale -- the preferred leafy green in the South (zones 7--10). Kale has more deeply lobed or curly leaves and is more cold-hardy -- the preferred leafy green in the North (zones 3--7). Collards are grown using similar cultural practices to kale but can be direct-seeded in summer in the South for fall and winter harvest.

title: "Growing Kale: Complete Garden Guide"

Edible curly kale Brassica oleracea with dense deep-green ruffled curly leaves growing from a central stem ready for harvest — Curly kale at peak harvest height. Image: AI-generated reference.

By Thomas Joseph Published 2026-06-10 Updated 2026-06-13 Reviewed by Thomas Joseph 9 min read

I don't grow kale at my Long Island plot — the beds are committed elsewhere. This guide is sourced from Cornell Cooperative Extension, Penn State Extension, NC State Extension, and UMass Extension, which collectively offer the most thorough published guidance on home kale production in the Northeast and mid-Atlantic.

Kale is among the hardiest, most cold-tolerant vegetables available to home gardeners. It is technically a biennial, and in zones 6—9 a fall-planted kale will often overwinter successfully and resume growth in spring before going to seed. Flavor improves substantially with cold temperatures — the standard advice that \"kale tastes better after a frost\" is grounded in real biochemistry: frost converts starches to sugars in the leaves.

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Variety selection

Brassica oleracea var. acephala encompasses kale and collard greens. Major kale types:

Curly kale: 'Dwarf Siberian' (50 days), 'Winterbor' (60 days), 'Redbor' (60 days, purple). Per Cornell Cooperative Extension, curly types are the most widely available and cold-hardy. 'Winterbor' is among the most cold-tolerant varieties available per Penn State Extension.

Lacinato/Dinosaur kale (B. oleracea var. acephala, Nero di Toscana group): 'Lacinato' (62 days), 'Black Magic' (57 days). Long, narrow, dark blue-green leaves with puckered texture. Milder flavor than curly types. Per NC State Extension, lacinato types are popular in markets and restaurants; excellent for year-round production.

Red Russian kale: 'Red Russian' (50 days). Flatter leaves, purple stems, very tender texture suited to salads. Per Johnny's Selected Seeds, Red Russian is the mildest-flavored kale type — preferred for raw applications. Less cold-hardy than curly types.

Kalette (kale sprouts): A hybrid of kale and Brussels sprouts producing small edible rosettes on the stem. Relatively new category; 'Kalettes Mix' available from specialty seed suppliers.

Days to maturity: 50 days ('Dwarf Siberian', 'Red Russian') to 62 days ('Lacinato').

Reader questions

Questions from other readers about this guide. Ask your own — if it's a good question, the answer goes here for the next reader.

When does kale taste best?

Per NC State Extension and Cornell, kale's flavor peaks after frost. Cold temperatures cause the plant to convert starches to sugars, producing sweeter, milder leaves. A kale plant that tasted slightly bitter in September will taste noticeably sweeter and more tender after the first hard frost in October. This is not folklore -- it is a documented physiological response to cold stress that is consistent across brassica species.

How do I harvest kale for continuous production?

Per Cornell Cooperative Extension, harvest outer leaves from the base of the plant, leaving the central growing crown intact. Never remove more than 1/3 of the plant's total leaf area at one time. This approach allows a single plant to produce leaves for 2--4 months or longer -- through the entire fall season in zone 7a and into winter if protected.

Can kale survive winter in zone 7a?

Established kale plants, particularly curly types like 'Winterbor' and 'Dwarf Siberian', can survive zone 7a winters with mulch protection. Per Penn State Extension, established plants tolerate temperatures down to approximately 10°F. In zone 7a, where winter lows typically stay above 0°F, covered plants often survive and resume growth in early spring. Mulch the base with 2--4 inches of straw after the first hard freeze to insulate roots.

What is the difference between kale and collard greens?

Both are Brassica oleracea var. acephala. Per NC State Extension, collard greens have large, smooth, flat leaves and are more heat-tolerant than kale -- the preferred leafy green in the South (zones 7--10). Kale has more deeply lobed or curly leaves and is more cold-hardy -- the preferred leafy green in the North (zones 3--7). Collards are grown using similar cultural practices to kale but can be direct-seeded in summer in the South for fall and winter harvest.

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Growing Kale: Variety Guide, Timing & Harvest Tips

Variety selection

Growing Kale: Variety Guide, Timing & Harvest Tips

Variety selection

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