How to Grow Alternanthera Red Knight

Alternanthera Red Knight

Alternanthera dentata 'Red Knight'

shrub

Alternanthera Red Knight is a vibrant ornamental foliage plant prized for its deep burgundy-red leaves with purple undersides. This tender perennial shrub is grown as an annual in most climates and adds dramatic color to garden beds, borders, and containers. It maintains a compact, bushy form and is popular in both landscape design and aquascaping.

Growing Conditions

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Sun: Full sun, 6-8 hours daily (more sun intensifies red coloration)

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Water: Keep soil consistently moist but not waterlogged; water when top inch of soil feels dry. Reduce watering in cooler months. Prefers humidity.

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Spacing: 12 inches

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Days to maturity: 30-45 days to decorative size

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Planting depth: Plant transplants at soil level; sow seeds 1/8 inch deep

Soil

Type: Well-draining loamy soil, rich in organic matter

pH: 6.0-7.0

Amendments:

Compost or aged manure Peat moss or coco coir Perlite or sand for drainage

Growing Zones

Find your zone →

Thrives in zones 10-11; grown as annual in zones 4-9

10a 10b 11a 11b

Growth Stages

Seedling

2-3 weeks

Tiny seedlings emerge with small oval leaves showing early red tinges. Very delicate and vulnerable to damping off.

Keep under grow lights, maintain 70-75°F, ensure high humidity, water gently from below, provide air circulation

Vegetative Growth

3-5 weeks

Plant develops bushy shape with increasing leaf production; red coloration becomes more pronounced with improved light and maturity.

Pinch growing tips every 2-3 weeks to encourage bushiness, feed with balanced fertilizer every 2 weeks, ensure full sun exposure

Established Growth

Ongoing through growing season

Full bushy form achieved with dense foliage; deep burgundy-red leaves are vibrant and glossy, purple undersides visible on mature leaves.

Deadhead any small inconspicuous flowers to encourage foliage production, fertilize weekly with diluted liquid fertilizer, maintain consistent moisture

Peak Color

Mid-summer through fall

Plant reaches maximum color intensity and ornamental appeal with rich deep red foliage throughout.

Maintain full sun, continue regular feeding, pinch as needed to maintain shape, monitor for pests in warm weather

Senescence/Winter Dormancy

Fall through winter

In cool climates, plant declines as temperatures drop below 50°F; leaves may lose color or plant may die back completely.

Bring containers indoors in zones 4-9, reduce watering, stop fertilizing, maintain 55-65°F indoors, or take cuttings for propagation

Companion Planting

Plan your garden →

Plant with:

Coleus Caladiums Begonias Dusty Miller Iresine Impatiens Ferns Sweet potato vine

Avoid planting near:

Plants requiring dry conditions Drought-tolerant succulents Plants competing for nutrients in confined spaces

Common Pests

Increase humidity, mist regularly, spray with neem oil or insecticidal soap, improve air circulation
Remove with alcohol-soaked cotton swab, spray with insecticidal soap or neem oil, isolate infested plants
Hand-pick or scrape off, spray with horticultural oil, treat with neem oil, prune heavily infested stems
Yellow sticky traps, spray with insecticidal soap, increase air circulation, neem oil applications

Uses

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Garden and Landscape Design

Household

Alternanthera Red Knight serves as a striking foliage accent in flower beds, borders, container gardens, and mixed plantings. Its intense red coloration provides excellent contrast to green or silver-foliaged plants and brightens shaded areas of the garden. [source]

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Container and Patio Gardening

Household

Its compact growth habit makes it ideal for pots, hanging baskets, window boxes, and mixed containers. Red Knight works beautifully as a thriller, filler, or spiller in container design schemes. [source]

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Aquascaping and Water Gardens

Household

Alternanthera varieties are popular aquatic stem plants used as background and mid-ground plants in freshwater aquariums. The red coloration requires high light and nutrients, making it prized by aquascapers. [source]

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Indoor Decorative Houseplant

Household

In colder climates, Red Knight can be grown indoors on bright windowsills or under grow lights. Its compact form and colorful foliage make it an attractive indoor accent plant. [source]

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Pollinator Plantings

Wildlife

While grown primarily for foliage, small flowers attract beneficial insects including bees and small butterflies. It provides shelter and food sources for garden insects. [source]

Harvest Tips

This is an ornamental foliage plant, not harvested for food. Pinch or prune stems regularly (every 2-3 weeks) to maintain compact bushy shape and encourage fuller color development. Take 3-4 inch stem cuttings anytime during growing season for propagation; cuttings root easily in water or moist soil within 1-2 weeks.

Fun Facts

🌱 Alternanthera Red Knight is sometimes called 'Joseph's Coat' due to its rich multicolored foliage that resembles the biblical coat of many colors; the purple-red coloration is more intense when grown in cooler temperatures and bright light.
🌱 This plant is easier to propagate from cuttings than from seed and will root in water within 1-2 weeks, making it simple to create new plants or overwinter specimens indoors.
🌱 In aquariums, Alternanthera plants can grow emersed (above water) or submersed (underwater), and the Red Knight variety is particularly prized because its vibrant red color intensifies under high-intensity aquarium lighting.

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