Kale

Growing Conditions

Growing Zones

Thrives in USDA Zones 3 - 10

Companion Planting

When to Plant

• Start Indoors

  6 - 8 weeks before last frost

• Transplant

  2 - 4 weeks before last frost

• Direct Sow

  3 months before first autumn frost

• Harvest

  55 - 75 days; harvest outer leaves and plant continues producing

Organic Growing Tips

• Use floating row covers from transplant to exclude cabbage white butterflies.

• Spray Bacillus thuringiensis (Bt) to control caterpillars without harming beneficial insects.

• Plant garlic nearby to repel aphids; interplant with nasturtiums as a trap crop for caterpillars.

• Top-dress with compost or worm castings mid-season and rotate brassicas to a new bed each year — feeding the soil prevents nutrient depletion and rotation breaks the disease cycles that weaken plants.

Common Pests

• Cabbage White Caterpillar
• Aphids
• Cabbage Looper
• Harlequin Bug
• Flea Beetle

Taxonomy

Kingdom

Plantae

Family

Mustard family (Brassicaceae)

Genus

Brassica

Species

Brassica oleracea var. sabellica

Natural History

Brassica oleracea is one of the most extraordinary examples of artificial selection in botany - a single wild coastal species whose different cultivated forms include kale, cabbage, broccoli, cauliflower, kohlrabi, Brussels sprouts, and collard greens, each representing selection pressure applied to a different part of the plant over centuries. Wild Brassica oleracea still grows on the limestone sea cliffs of Britain and Brittany; it is a modest, unremarkable small shrub that gives little hint of its descendants. Kale and collard-type forms - selected for leafy growth rather than heads or modified flower buds - are among the oldest domesticated brassicas, likely cultivated around the Mediterranean from Greek and Roman times. In Scotland, kale was so fundamental to the peasant diet for centuries that the kitchen garden was called a kail yard, and the word kail was used generically for any cooked greens. The phrase "dinner o' kail" was simply the Scots word for the evening meal. The 21st-century kale revival - driven by interest in its glucosinolate chemistry, mineral density, and eye pigments - is historically unusual in restoring a medieval peasant staple to elite cultural status.

Traditional Use

Kale is among the oldest cultivated brassicas, grown in some form since Greek and Roman times. For most of European history it was a winter staple food for peasant populations in northern climates - the kail yard was the kitchen garden itself - rather than an elite vegetable.

• Ancient Greek and Roman Cultivation - Leaves

  Pliny the Elder's Naturalis Historia describes multiple forms of Brassica oleracea including loose-leafed types consistent with kale or colewort. Cato's De Agricultura (160 BCE) discusses brassica cultivation in terms suggesting a range of leaf types were grown. Colewort - the name used in Britain for loose-leafed brassicas through the medieval period - appears in Roman agricultural writing as a significant garden crop.

• Scottish Kail Yard and Northern Winter Food - Leaves

  In Scotland, the kitchen garden derived its name - kail yard - entirely from the centrality of kale to the rural diet. Kale and oats were the primary winter foods for much of the Scottish population through the medieval and early modern periods. The word kail was used as a generic term for any cooked green vegetable. The phrase "come in for your kail" was an invitation to dinner. This intimate relationship between kale and everyday Scottish life is documented in household records, poetry, and the Kailyard School of literature in the 19th century.

• Italian Lacinato and Tuscan Tradition - Leaves

  Lacinato kale - cavolo nero, dinosaur kale, or Tuscan black kale - is a distinct Italian type with long bumpy dark leaves that predates the curly northern European forms. It appears in Italian agricultural records from at least the 18th century in Tuscany, where it is essential in ribollita soup and braised winter greens preparations. The variety name Lacinato is associated with a village near Florence.

• World War II Victory Garden Promotion - Leaves

  During World War II, the British government promoted kale cultivation as part of the Dig for Victory campaign because it was cold-hardy, productive through winter, nutritionally dense, and grew in almost any garden. The Ministry of Food distributed kale cultivation guidance widely. This wartime emphasis kept kale in common allotment use through the latter 20th century and provided the horticultural foundation for its global revival as a health food in the 2010s.

This information is provided for historical and educational purposes only and is not medical advice. Always consult a qualified healthcare professional before making decisions related to your health.

Morphology (Plant Structure & Identification)

• Root System

  Strong branching root system with a central taproot and many feeder roots. Plants anchor well and keep drawing nutrients during cool weather.

• Stem

  Upright central stem that lengthens as lower leaves are harvested. Older plants can become woody at the base but continue producing tender leaves near the top.

• Leaves

  Large leaves vary from curled and ruffled to flat, bumpy, or strap-like depending on type. Leaf texture, blue-green color, and waxy surface are useful for distinguishing varieties.

• Flowers

  Yellow four-petaled brassica flowers appear on tall stalks when plants bolt or overwinter into spring. Flower buds resemble small raab and signal a shift away from leaf production.

• Fruit

  Produces slender seed pods called siliques after flowering. The harvested crop is the leaf, usually picked from the outside while the growing tip remains intact.

Known Varieties

Common cultivars worth knowing

• Lacinato

  Dark blue-green Italian kale with long bumpy leaves and excellent flavor.

  Best for: soups, sauteing

• Winterbor

  Very curly hybrid with strong cold tolerance and high yields.

  Best for: winter harvests

• Red Russian

  Flat, tender leaves with purple stems and mild flavor.

  Best for: salads, quick cooking

• Vates Blue Curled

  Compact curled type with reliable production and good cold tolerance.

  Best for: small gardens, freezing

• Dwarf Siberian

  Hardy, broad-leaved type that grows quickly in cool conditions.

  Best for: early greens, cold climates

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