Purple Prince Alternanthera (Alternanthera dentata 'Purple Prince')
all-ter-NAN-ther-ah den-TAY-tah 'Purple Prince'

Annual (usually grown as an annual near you) in the Amaranthaceae Family
Purple Knight Alternanthera is a bold, upright annual with deep purple-ruby, almost-black foliage — a strong vertical color accent for beds and containers.

Purple Knight is a larger, more upright selection of Alternanthera dentata, distinct from the low mounding or thread-leaved Alternanthera types. Its broad leaves emerge deep ruby-purple, darkening to nearly black in strong sun and heat, on a plant that typically reaches 16-20 inches tall and 18-36 inches wide. Some growers also sell this plant, or a very similar unpatented selection, under the name 'Purple Prince'; 'Purple Knight' is the more consistently used and widely documented trade name. In Chicago (zone 5b) it is grown exclusively as a warm-season annual, since it has no winter hardiness here and is only truly perennial in tropical climates. Its upright habit and dark, saturated color make it a strong thriller or backdrop plant in mixed containers and beds.

Pros

  • Bold, upright habit adds vertical structure and color contrast
  • Deep purple-black foliage holds color all season without deadheading
  • Heat and humidity tolerant, thrives in Chicago summers
  • Easy care with minimal pest or disease issues

Cons

  • Not cold hardy in zone 5b; needs replacing as a new annual each year
  • Foliage color washes out in heavy shade
  • Can get leggy without occasional pinching back
  • Trade name inconsistency ('Purple Prince' vs 'Purple Knight') can cause mislabeling
 

Plant Data

Mature Size 16 - 20 inches tall. 18 - 36 inches wide.
Tags Annual, Annual in Chicago, Colorful Foliage, Deer Resistant, Evergreen, Grown For Attractive Foliage, Potentially Toxic, Rabbit Resistant, Tender Perennial, Thrillers
Foliage Color

Photos of This with...

Serena Rose Summer Snapdragon, Gold Mound Pigeon Berry, Colorblaze Dark Star Coleus, Lemon Coral Stonecrop, Charged Up Campfire Coleus, Persian Shield, Vittata Moses-in-a-basket,
 
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Pricing and Availability History

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Past Availability
2025 : 02/05 - 06/22
2024 : 02/08 - 06/15
2023 : 03/02 - 05/21

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Field-Grown vs. Greenhouse-Grown Plants

Plants which are well-adapted to our local climate are most often field-grown (outside). Field-grown plants are generally cheaper and have the advantage of already somewhat acclimated to our cold winters, but that means they’re not artificially far along in the spring and tend to bloom at the normal time in our area.

Spring annuals and tender perennials are typically grown in Greenhouses so they can be ready and luxurious exactly when customers want them. Some perennials are also “forced” into early bloom in greenhouses. In May, there can be a very big difference between field-grown and greenhouse-grown plants of the same type. The latter typically look good right away (so they’re a great choice where that’s important), but we typically pay a premium for it.


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No Pricing or Availability Right Now

We order from a rotating cast of the best nurseries in the Great Lakes region. It looks like we've offered this plant in the past, but the nurseries we're working with this week don't appear to have it in stock at the moment.

Our goal is to bring as many plants together under "one roof" as possible, so we'll try hard to make it available again in the future!