Kale (Brassica oleracea (Acephala Group) 'Redbor')

Overview

Brassica oleracea (Acephala Group) ‘Redbor’ is a spectacular cool-weather annual prized for its vibrant foliage rather than its rarely seen flowers. This cultivar of Kale features intensely colored, purple-red, ruffled leaves layered in an upright rosette, adding superb texture and color contrast to late-season landscapes. As an ornamental foliage plant, it outperforms many traditional bedding plants when temperatures cool down.

This variety of Kale thrives when ambient temperatures are cool, developing its deepest, most attractive coloration as night temperatures drop in the fall. While technically a biennial, it is successfully grown as a fast-maturing accent annual, providing visual interest long after summer annuals have faded. Gardeners appreciate this plant for its robust structure and low maintenance requirements throughout its growing season.

The intensity of the foliage color on Brassica oleracea (Acephala Group) ‘Redbor’ is directly linked to cool conditions; consistently hot weather, above 80°F daytime highs, will cause the plant to grow poorly and suffer color loss. Plan your planting schedule around the fall season for peak ornamental performance in most regions.

Fast Facts

• Plant Family: Brassicaceae
• Plant Type: Annual
• Hardiness Zones: USDA Zones 2-11
• Size at Maturity:
  • Height: 1-1.5 ft
  • Spread: 1-1.5 ft
• Bloom Time: Flowers not showy
• Bloom Description: Rarely flowers
• Sun Exposure: Full sun
• Water Needs: Medium
• Maintenance Level: Low

How to Grow

For optimal display, Brassica oleracea (Acephala Group) ‘Redbor’ must experience cool temperatures. Start seeds indoors around July 1st if you are aiming for a mid-August planting outdoors for fall color. These plants prefer organically rich, consistently moist, well-drained loams. Plant seedlings out once temperatures are reliably moderate.

Watering should remain consistent to keep the soil evenly moist, as this prevents stress that can hinder leaf color development. Full sun is ideal, but if you must grow this Kale during warmer summer transitional periods, afternoon shade may be necessary for survival, though deep color intensity will suffer until cooler weather returns.

If grown for fall interest, the foliage remains highly attractive even after several frosts, often persisting into late fall or early December, depending on your climate zone. In mild winter areas, the plants may survive the winter, but remember to promptly remove any flower stems that emerge in the spring to redirect energy back into the foliage. These plants also perform exceptionally well when grown in containers.

Landscape Uses

This ornamental Kale is incredibly versatile, lending its dramatic texture to nearly any cool-season display. Use the upright, ruffled foliage of Brassica oleracea (Acephala Group) ‘Redbor’ to create strong accents in border fronts, providing structure where lower-growing bedding plants might fade. It works wonderfully as an edging material to define garden beds or add dramatic impact to window boxes and containers.

Design-wise, pair the deep purple-red hues of ‘Redbor’ with complementary textures and colors available during the cooler months. Mix them alongside late-blooming chrysanthemums, upright ornamental grasses, or silvery asters to create layered, autumnal displays. While primarily ornamental, the leaves are edible—though gardeners note the taste is slightly inferior when compared to kales specifically bred for vegetable production.

As an annual accent, this Kale provides reliable, long-lasting color well into the dormant season. The contrast between the deep red leaves and any residual greens or silvers in the garden adds depth and sophistication to transitional plantings.

Standout Features

Flower Qualities

• Insignificant

Noteworthy Characteristics

Ornamental cabbages and kales are cultivated primarily for their foliage, unlike their vegetable cousins which form heads. Ornamental kale, like ‘Redbor’, produces curly, ruffled leaves in a tight rosette, developing showy colors—in this case, purple-red with silver tones—as night temperatures drop. This biennial is treated as an annual, reaching about 18 inches tall, and its intensely colored leaves add significant texture and interest from fall until frost or even winter.

Tolerances

• None listed

Potential Problems

Gardeners should remain vigilant for common brassica pests, particularly when foliage is young. Watch closely for signs of feeding by cabbageworms, cabbage loopers, and various caterpillars, which can quickly devour leaves. Flea beetles, thrips, slugs, and aphids also pose threats and require routine scouting and treatment.

Root maggots can become established in certain soil types, causing root damage that weakens the entire plant. To manage disease potential, which includes leaf spots, blackleg, black rot, and yellows, ensure excellent soil drainage and avoid planting Kale in the same spot year after year. Prompt removal of spent plants is crucial for minimizing overwintering disease spores.

Frequently Asked Questions

What hardiness zones is Kale suitable for?

Kale, including the ‘Redbor’ cultivar, is uniquely tolerant, suitable for USDA Zones 2 through 11.

How large does Kale (Brassica oleracea (Acephala Group) ‘Redbor’) grow?

This ornamental variety generally reaches a height between 1 and 1.5 feet, with a similar spread of 1 to 1.5 feet.

What sun exposure does Kale (Brassica oleracea (Acephala Group) ‘Redbor’) need?

For best color development, Brassica oleracea (Acephala Group) ‘Redbor’ requires full sun exposure throughout the growing period.

When does Kale bloom?

Blooms are not showy, with this ornamental variety rarely flowering when grown under ideal cool-weather annual conditions.

Conclusion

The ‘Redbor’ Kale is an indispensable cool-season performer, delivering outstanding textural interest and deep purple-red color when most other plants are slowing down. Its low maintenance needs and adaptability make Brassica oleracea (Acephala Group) ‘Redbor’ a favorite for late-season containers and borders. Ensure you calculate your sowing or transplant dates to capture the crucial cool night temperatures required for the best foliage display in your garden.

Companion Planting

Companion planting with Kale involves selecting neighbors that share similar cool-weather preferences and water needs. Pairing ‘Redbor’ with other cool-season favorites like pansies, violas, or fall-blooming snapdragons can enhance visual appeal while sharing cultural requirements. Avoid planting near heavy feeders unless you are aggressively amending the soil, as Kale benefits from consistent, balanced nutrients.

Since this Kale variety is grown for visual impact, design companions to contrast its texture. For instance, planting next to fine-textured ornamental grasses or plants with flat, broad leaves (like mums) emphasizes the ruffled nature of the foliage. These combinations thrive under the same medium water regime and full sun to partial shade conditions that define cool-weather gardening.