How to Grow Purple Tower
Wikimedia Commons
Purple Tower
Alternanthera dentata 'Purple Knight'
shrubPurple Tower is an ornamental foliage plant prized for its deep burgundy to near-black leaves that create striking vertical accents in gardens and containers. It grows as a compact, upright shrub with lance-shaped leaves and maintains its dramatic coloring throughout the growing season. This tender perennial is often grown as an annual in cooler climates.
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Example Purple Tower timeline · Pittsburgh, PA (Zone 6b)
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Plant Purple Tower
Around Apr 17Near Pittsburgh's average last spring frost.
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Tend & protect
Late spring–summerWatering, feeding, and pest-watch reminders.
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Harvest Purple Tower
Around Jun 1≈ 45 days after planting
Sample dates for Pittsburgh, PA. Sign up to get exact Purple Tower dates for your own zip code.
Growing Conditions
Soil
Growing Zones
Find your zone →Thrives in zones 10b-12 as a perennial; grown as an annual in zones 3-10
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Seedling
2-3 weeksTiny seedlings emerge with simple oval leaves, pale green initially. Growth is slow in first 2-3 weeks.
Keep soil warm (70-75°F) and consistently moist. Provide bright light immediately after germination to prevent leggy growth. Thin seedlings to prevent crowding.
Juvenile Growth
3-4 weeksPlants develop characteristic lance-shaped leaves and begin showing purple coloration. Stems elongate and branching increases.
Pinch back growing tips to encourage bushier growth. Begin weekly feeding with balanced fertilizer. Ensure 6+ hours of direct sun for color development. Transplant to larger containers if needed.
Vegetative/Foliage Development
4-6 weeksPlant reaches desired height and fullness with deep burgundy to nearly black foliage. Leaves are fully formed and mature in color.
Continue pinching tips for compact form. Maintain consistent moisture and nutrition. Monitor for pests. Full sun maximizes color intensity.
Blooming
6-8 weeks (can bloom throughout season)Small, inconspicuous white to pale pink flowers appear along stems. Flowers are not the main ornamental feature.
Deadhead spent flowers to redirect energy to foliage. Optional—many growers remove buds to maintain focus on leaf color. Continue regular feeding and watering.
Maintenance/Harvest Season
8+ weeks until frostPlant maintains full purple foliage in containers or landscape beds. No traditional harvest, but leaves can be used fresh.
Prune as needed to maintain shape and prevent legginess. Continue weekly fertilization. Remove any reverted green foliage. Before frost, take cuttings to overwinter indoors.
Companion Planting
Plan your garden →Plant with:
Avoid planting near:
Common Pests
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Spray with insecticidal soap or neem oil every 7 days. Inspect undersides of leaves regularly. Use reflective mulches to deter. Introduce parasitic wasps.
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Mist foliage regularly to increase humidity. Spray with neem oil or miticide. Remove heavily infested leaves. Avoid over-fertilizing with nitrogen.
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Remove with alcohol-soaked cotton swab. Spray with insecticidal soap. Treat with neem oil weekly until resolved. Isolate infested plants.
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Scrape off manually. Spray with horticultural oil in dormant season. Apply systemic insecticide if severe. Monitor regularly.
Uses
Landscape Color Accent
OrnamentalPurple Tower creates dramatic vertical interest in garden beds, borders, and container gardens with its deep burgundy foliage. It serves as an excellent backdrop or accent plant in mixed plantings and tropical-style gardens. [source]
Floral Arrangements & Flower Design
CraftFresh purple foliage branches are prized by florists and designers for adding depth, texture, and dark tones to fresh and dried flower arrangements. The leaves hold well in water and maintain color for extended periods. [source]
Container Gardening
HouseholdPurple Tower excels in pots, planters, and mixed containers on patios and decks, providing consistent color and structure throughout the season. It works well as a thriller plant in mixed containers with spillers and fillers. [source]
Edible Ornamental Garnish
CulinaryYoung purple leaves are technically edible and can be used as a striking garnish for plates and salads, though flavor is mild. Use sparingly as a visual accent rather than a major ingredient. [source]
Pollinator Support
WildlifeThe inconspicuous flowers attract small pollinators and beneficial insects. While not a major nectar source, it provides foliage shelter for beneficial bugs and light feeding opportunities. [source]
Harvest Tips
Purple Tower is grown for ornamental foliage rather than harvest. Cuttings can be harvested year-round for propagation by pinching 3-4 inch stem tips. Fresh leaves can be used in floral arrangements. Before first frost in cooler zones, take 4-6 inch cuttings and root in water or moist perlite indoors to overwinter.
Fun Facts
- 🌱 Purple Tower is a cultivar of Alternanthera dentata, also known as Brazilian Joyweed, and was specifically selected for its deep purple coloration—some leaves are so dark they appear almost black.
- 🌱 The plant's burgundy color intensifies in full sun and cooler temperatures; growing it in part shade or warm conditions will result in more brownish or greenish-purple tones.
- 🌱 In frost-free zones, Purple Tower can be overwintered and will grow into a larger shrub year after year, though it's typically treated as an annual in temperate climates and easily propagated from cuttings taken before winter.
Gardening Terms
New to gardening? Learn about terms used in this guide:
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