FlowerFoliage
Alternanthera Purple Knight
Ornamental Foliage
Purple Knight is a stunning ornamental foliage plant that transforms garden spaces with its rich purples and deep reds. This cultivar of Alternanthera dentata matures into a compact mounded shrub perfect for borders, walkways, and container gardens across zones 9-11. Reaching 18-24 inches tall and ready to display its exotic color in just 70-79 days, Purple Knight thrives in partial shade and brings year-round warmth vibes to humid North American gardens.
Photo © True Leaf Market
Growing Conditions
USDA Zone
9-11
Sunlight
Partial Shade
Water
Moderate
Soil
Well-drained, Fertile Loam
Preferred Temp65-85°F
Growth Stats
24 in
Height
—
Width
36 in
Spacing
70–79
Days to Harvest
PeriodPerennial
TypeForb/herb, Shrub, Vine
Plant Profile
Sunlight
Partial Shade
Water
Moderate
Zones
9-11
Size
24in H x ?in W
Growth
Perennial
Care
High
Hover over chart points for details
Highlights
What sets Purple Knight apart is its dramatic, jewel-toned foliage that creates striking visual contrast in any garden design. The plant's naturally tidy mounding habit means it looks polished with minimal pruning, making it ideal for gardeners who want impact without constant maintenance. Native to the warm climates of Asia, Africa, and Australia, this annual ornamental brings an exotic elegance that elevates even simple garden compositions.
Common Uses
Purple Knight is grown exclusively for its ornamental foliage rather than for culinary purposes. Gardeners use it to create striking visual borders along walkways and fence lines, where its deep purple and red tones add drama and sophistication. It also excels in container plantings and mixed beds where its compact mounding form provides structure and year-round color.
Growing Timeline
First Bloom
Non-flowering
First Harvest
Not Applicable
Last Harvest
Not Applicable
Care Instructions
Start Indoors
Start Purple Knight seeds indoors 6-8 weeks before your last spring frost to ensure strong transplants ready for the garden. Keep soil warm and consistently moist until germination occurs. Provide bright light once seedlings emerge to encourage compact, stocky growth.
Transplant Outdoors
Transplant Purple Knight outdoors after all danger of frost has passed and soil has warmed. Harden off seedlings by gradually exposing them to outdoor conditions over 7-10 days. Space plants 36 inches apart in their final location.
Pruning
Purple Knight's naturally mounded growth habit requires minimal pruning to maintain its neat appearance. Pinch back young plants early in the season to encourage bushier, more compact growth. Light trimming of wayward stems keeps the plant looking tidy, but resist heavy pruning that might compromise the full mounding form.
Growing Calendar
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Companion Planting
Ecology & Traits
Scientific Classification
Alternanthera brasiliana (L.) Kuntze
Family
Amaranthaceae
Genus
Alternanthera
Duration
Perennial
Growth Habit
Spreading
Native Status
L48 (I)HI (I)PR (I)VI (I)
History & Origin
“Purple Knight traces its lineage to Alternanthera dentata, a tropical foliage plant native to the warm regions of Asia, Africa, and Australia. This cultivar was developed to capture the exotic beauty of its parent species while adapting to the conditions of North American gardens. The variety represents careful selection for the rich purple and red coloration that makes it stand out among ornamental foliage options.”