How to Grow Canna Black Knight

Canna Black Knight

Canna × generalis 'Black Knight'

flower

Canna Black Knight is a striking tropical ornamental featuring deep burgundy to near-black foliage with vibrant red flowers that bloom throughout summer and fall. This tall, bold cultivar is prized for its dramatic color contrast and architectural presence in gardens. It's a tender perennial that brings exotic flair to borders, containers, and water garden edges.

Growing Conditions

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Sun: Full sun, 6-8 hours daily for best blooming; tolerates partial shade but flowers may be less abundant

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Water: Keep soil consistently moist to wet; water deeply and regularly during growing season. Cannas thrive in boggy conditions and even shallow water. Reduce watering in winter dormancy.

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Spacing: 18-24 inches

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Days to maturity: 60-90 days to first flowers from planting

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Planting depth: 4-6 inches; rhizomes should be covered with 2-3 inches of soil

Soil

Type: Rich, consistently moist to boggy soil

pH: 6.0-7.0

Amendments:

Compost aged manure peat moss or coco coir perlite for container draining

Growing Zones

Find your zone →

Thrives in zones 7b-11; grow as annual in cooler zones or dig rhizomes for winter storage

7b 8a 8b 9a 9b 10a 10b 11a 11b

Growth Stages

Dormancy & Sprouting

2-4 weeks

Rhizomes are planted in spring after last frost. Eyes begin to sprout as soil warms; leaf shoots emerge from the rhizome.

Plant rhizomes in warm soil (at least 60°F). Water moderately until active growth begins. Ensure good drainage in containers.

Vegetative Growth

4-8 weeks

Large, paddle-shaped leaves unfurl in dramatic deep burgundy tones. Plant grows tall and full, developing multiple stems from the rhizome.

Water consistently and generously. Apply balanced fertilizer every 2-3 weeks. Mulch around base to retain moisture. Stake tall varieties if needed.

Budding

1-2 weeks

Flower buds form at the top of stems, nestled within the leaf sheaths. Buds develop color and prepare to open.

Continue regular watering and feeding. Watch for pests. Ensure adequate sunlight for bud development.

Flowering

8-12 weeks or until frost

Bold red flowers bloom in clusters at stem tips. Flowers open successively along the inflorescence. Dark foliage creates striking contrast.

Deadhead spent flowers to encourage continued blooming. Keep soil moist but not waterlogged. Feed every 3-4 weeks with lower-nitrogen fertilizer.

Dormancy & Storage

4-6 months

After first frost, foliage blackens and dies back. Plant stops flowering and enters rest period.

In zones 7b-8, dig rhizomes after first frost, brush off soil, air-dry 1-2 weeks, and store in cool (50-60°F), dry location with peat moss. In warmer zones, leave in ground with heavy mulch or keep as year-round planting.

Companion Planting

Plan your garden →

Plant with:

Hibiscus elephant ear coleus impatiens ferns ornamental grasses daylilies Russian sage

Avoid planting near:

Plants requiring dry soil drought-tolerant species shallow-rooted plants competing for nutrients

Common Pests

Spray with water to dislodge; use insecticidal soap or neem oil if infestation is heavy
Hand-pick early morning; use pheromone traps placed away from plants; apply spinosad or neem oil
Remove affected leaves; use Bt (Bacillus thuringiensis) spray; maintain good air circulation
and
Remove by hand; apply slug bait or diatomaceous earth; create physical barriers
Spray undersides of leaves with insecticidal soap or horticultural oil; use yellow sticky traps

Uses

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Edible Tubers

Culinary

Canna rhizomes have been cultivated for centuries in tropical regions as a starch-rich food crop similar to potatoes. The tubers contain high levels of carbohydrates and are traditionally cooked and eaten. [source]

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Cut Flowers & Arrangements

Household

Bold red flowers and exotic dark foliage make stunning cut flower arrangements and tropical floral designs. The dramatic form works well in both modern and cottage garden arrangements. [source]

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Pollinator Support

Wildlife

Canna flowers attract hummingbirds, bees, and butterflies seeking nectar throughout the blooming season. The plant provides essential food resources for pollinators. [source]

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Ornamental Landscaping

Craft

The striking architectural form, bold foliage color, and vibrant flowers make Canna Black Knight a focal point plant for tropical, contemporary, and cottage garden designs. Works well in large containers, water gardens, and mixed borders. [source]

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Traditional Herbal Use

Medicinal

In traditional medicine systems, particularly in Southeast Asia and India, Canna plants have been used for inflammation relief and digestive support, though scientific validation is limited. [source]

This is not medical advice. LizPlants is not a medical resource. Always consult a qualified healthcare professional before using plants medicinally.

Harvest Tips

Canna is grown for ornamental flowers and foliage; cut flowers last 7-10 days in water, harvesting when lowest florets on the spike are beginning to open. To extend blooming season, regularly remove fully spent flower spikes at the base. Deadheading redirects energy into new buds rather than seed development.

Fun Facts

🌱 Canna Black Knight's deep burgundy foliage contains anthocyanin pigments, the same compounds found in blueberries and red wine, which give the leaves their striking dark color.
🌱 Cannas have been grown as food crops for over 5,000 years; archaeologists have found evidence of Canna cultivation in pre-Columbian South America.
🌱 The name 'Canna' comes from the Greek word for 'reed,' referencing the plant's upright, architectural stem structure and tropical appearance.

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