Botanical Classification
Redbor kale, scientifically classified as Brassica oleracea var. acephala, belongs to the Brassicaceae family, which includes cruciferous vegetables such as cabbage, broccoli, and Brussels sprouts. The acephala variety indicates non-heading brassicas, meaning it forms a loose rosette of leaves rather than a compact head.
Redbor is a specific hybrid cultivar of curly kale, bred for its striking color and ornamental appeal, sharing its genetic lineage with other kale varieties derived from wild Mediterranean cabbage. Its classification places it alongside other leafy greens selected for their edible and aesthetic qualities.
Origin and History
Kale has ancient roots in the eastern Mediterranean and Asia Minor, cultivated since around 2000 BCE by Greeks and Romans. Curly kale varieties, including Redbor’s predecessors, became staples in northern Europe during the Middle Ages for their cold tolerance. Redbor kale, a modern hybrid, was developed in Europe, likely in the Netherlands or Germany, in the late 20th century for its vibrant burgundy coloration, blending culinary and decorative appeal. Its name reflects its rich hue.
Popularized in the U.S. during the 21st-century health food movement, Redbor is now widely grown in , valued by gardeners and chefs for its aesthetic and nutritional benefits.
Identifying Characteristics
Redbor kale is a striking plant, known for its deeply curled, frilly leaves in vibrant shades of purple, burgundy, or magenta, which intensify with cooler temperatures. The leaves, similar to curly kale, grow in a loose rosette around a sturdy central stem, reaching heights of 2-5 feet, making it one of the tallest kale varieties. The foliage has a crinkled texture, and the stems are purple, edible when young but toughening with age.
Its vivid color and upright growth make Redbor a favorite for ornamental gardens, borders, and edible landscapes, distinguishing it from greener kale varieties.
Taste
Redbor kale has a robust, slightly bitter, and peppery flavor, akin to curly kale, with a mild cabbage-like undertone. Its texture is crisp and sturdy, though less fibrous than standard curly kale, especially when harvested young.
Cooking, such as steaming or sautéing, softens its bitterness, revealing a savory, earthy taste, while light frosts enhance sweetness by converting starches to sugars. Raw, it benefits from massaging with oil or acid to tenderize and mellow its flavor, making it suitable for bold, flavorful dishes.
Seasons/Availability
Redbor kale is a cool-season crop, thriving in temperatures between 7-24°C (45-75°F), with frost tolerance down to -12°C (10°F). In the USA, it’s planted in early spring (February-March) or late summer (July-August), maturing in 50-70 days, and is typically available from late spring (April-May) through early winter (November-December).
It grows well in USDA zones 2-11, with major production in California, Oregon, and the Northeast. Peak flavor and color occur in fall after frosts, and it’s harvested year-round in milder climates like coastal California. Redbor is available fresh in U.S. supermarkets, farmers’ markets, and CSA programs, often as mature or baby leaves, with year-round supply supported by greenhouse cultivation.
Culinary Uses
Redbor kale’s vibrant color and hearty texture make it a versatile ingredient in American cuisine. Raw, its leaves are massaged for salads, pairing well with citrus dressings, nuts, or cheeses to balance its slight bitterness, adding visual appeal to plates. It’s used in smoothies for a nutrient boost, retaining its vivid hue.
Cooked, Redbor excels in soups, stews, or sautéed dishes with garlic and olive oil, holding its structure well. It’s also baked into kale chips for a colorful, crispy snack. Young stems are edible, while mature ones can flavor broths, offering zero-waste potential in dishes from casual to gourmet across the U.S.
Nutritional Value
Redbor kale is a nutritional powerhouse, low in calories (approximately 35 per cup raw) and rich in vitamins, minerals, and antioxidants. It’s an exceptional source of vitamins K, A, and C, providing over 100% of daily requirements per serving, supporting blood clotting, vision, and immune health.
It contains 2-3 grams of fiber per cup, promoting digestion, and is high in calcium, iron, and magnesium for bone and blood health. Its deep purple color indicates high levels of anthocyanins, antioxidants with anti-inflammatory and heart-protective properties, alongside quercetin and kaempferol. Redbor also offers folate and omega-3 fatty acids, making it a valuable addition to plant-based diets.
Cultivation of Redbor Kale
- Climate and Season: Redbor kale thrives in cool weather, with optimal temperatures between 7-24°C (45-75°F), and tolerates frosts down to -12°C (10°F). In the USA, plant in early spring (February-March) or late summer (July-August) for spring and fall harvests. It grows in USDA zones 2-11, with year-round cultivation in mild areas like coastal California and peak fall harvests in colder regions like Vermont.
- Site Selection: Choose a site with full sun (6-8 hours daily) to enhance vibrant leaf color, though partial shade is tolerated in warmer states like Texas or Florida to prevent bolting. Ensure good air circulation to reduce fungal disease risk, particularly in humid areas like the Southeast.
- Soil Requirements: Prefers fertile, well-drained, loamy soil with a pH of 6.0-7.5. Enrich with organic matter like compost or aged manure. In regions with clay soils (e.g., Midwest) or sandy soils (e.g., Southeast), amend with compost to improve drainage and fertility for robust leaf and stem growth.
- Soil Preparation: Loosen soil to 12 inches deep, mixing in 2-3 inches of compost or organic matter. Remove rocks and debris to support root development. Conduct a soil test through local extension services (e.g., USDA’s NRCS) to confirm pH and nutrient levels, adjusting with lime or sulfur as needed.
- Planting: Sow seeds ¼-½ inch deep, spacing 12-18 inches apart in rows 18-24 inches apart to accommodate its 2-5 foot height. Transplant seedlings started indoors 6-8 weeks earlier for faster growth, common in shorter-season areas like Minnesota. In warmer regions like California, direct sowing is effective.
- Watering: Maintain consistent soil moisture, providing 1-1.5 inches of water weekly, adjusting for rainfall. Use drip irrigation, popular in arid states like Arizona, to keep leaves dry and reduce disease risk. Mulch to retain moisture, especially in hot, dry regions like the Southwest.
- Fertilization: Apply a balanced fertilizer (e.g., 10-10-10) at planting, followed by a nitrogen-rich fertilizer (e.g., fish emulsion) every 4-6 weeks to promote leafy growth. Avoid over-fertilizing, which can attract pests in humid areas like the Gulf Coast and reduce leaf color intensity.
- Mulching: Add a 2-3 inch layer of organic mulch, such as straw, wood chips, or shredded leaves, to conserve moisture, suppress weeds, and keep roots cool. This is critical in regions with temperature swings, like the Midwest, or hot summers, like the Southeast, to stabilize soil conditions.
- Pest Management: Monitor for pests like aphids, cabbage worms, and flea beetles, common in U.S. brassica crops. Use floating row covers in organic farms (e.g., Oregon), neem oil, or introduce beneficial insects like ladybugs, popular in California. Hand-pick caterpillars for small gardens, effective nationwide.
- Disease Control: Prevent fungal diseases like powdery mildew and black rot, prevalent in humid regions like the Southeast, by ensuring air circulation and avoiding overhead watering. Rotate crops every 2-3 years, standard in intensive farming states like California, to reduce soil-borne pathogens.
- Harvesting: Harvest outer leaves when 6-8 inches long, about 50-70 days after planting, cutting close to the stem to encourage regrowth. Start in late spring (April-May) or fall (September-November), with sweeter, more vibrant leaves post-frost in colder states like New York. Regular harvesting extends yield.
- Succession Planting: Sow seeds every 2-3 weeks in spring or fall for a continuous supply, a common practice in mild climates like California’s Central Valley. In shorter-season regions like Wisconsin, focus on spring and late summer plantings to maximize harvests before hard freezes.
- Storage and Preservation: Store fresh Redbor kale at 0-4°C (32-40°F) in a perforated plastic bag in the refrigerator for up to 2-3 weeks, standard for U.S. households. For long-term storage, blanch leaves for 2-3 minutes, cool in ice water, dry thoroughly, and freeze to preserve nutrients and color. Wash and dry before storing to maintain freshness.