Blue Knight Butterfly Bush (Buddleja davidii 'Blue Knight')
Buddleja dah-VID-ee-eye 'Blue Knight'

Deciduous Perennial Shrub in the Scrophulariaceae Family
Compact Monarch® series butterfly bush with rich blue-purple blooms from late summer into fall.

Buddleja 'Blue Knight' is part of Walters Gardens' Monarch® Collection, bred by Hans A. Hansen from a 2010 cross of 'Podaras #8' and 'Blue Chip', and patented in 2017 (US PP28,178). Unlike the much taller classic 'Black Knight', it's a compact, rounded shrub, 3.5-4ft tall and 6-7ft wide, that opens light lavender-purple and deepens to rich blue-purple. Fast growing and fragrant, it blooms from late summer into fall, often continuing until frost, and draws butterflies, bees, and hummingbirds.

Pros

  • Rich blue-purple flower spikes that deepen in color as they open
  • Compact, rounded habit - smaller than classic butterfly bush types
  • Fast growing and fragrant; blooms late summer into fall, often until frost
  • Deer resistant

Cons

  • Needs full sun to perform well
  • Can die back to the ground in colder zones, regrowing from the roots in spring
  • Compact size means less dramatic impact than full-sized butterfly bush types
Highlights Reblooms Fragrant Attracts Pollinators
 

Plant Data

Mature Size 4 - 4 feet tall. 6 - 7 feet wide.
Growth Rate Fast
Sun Exposure Full Sun - Full Sun
Moisture Tolerance Dry - Medium
Zones 5a - 10a (Usually hardy to -20° F)
Tags Attracts Birds, Attracts Butterflies, Attracts Hummingbirds, Attracts Pollinators, Container, Deciduous, Deer Resistant, Drought Tolerant, Dry, Edging, Extended Bloom Time, Fragrant, Fragrant Flowers, Full Sun, Good for Beginners, Good for Borders, Good for Butterfly Garden, Good for Cottage Garden, Good for Cut Flowers, Good for Hedges, Good for Mass Planting, Low Maintenance, Medium, Most Popular, Non-Allergenic, Normal Soil, Perennial, Prairie Garden, Rabbit Resistant, Reblooms, Showy Flowers, Shrub, Thrillers, Tolerant of Hot Dry Site, Tolerant of Loamy Soil, Tolerant of Moist Soil, Well-Drained Soil
Bloom Period July - October
Flower Color Blue-Purple
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Pricing and Availability History

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Past Availability
2025 : 04/13 - 08/09
2024 : 05/16 - 07/20

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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.


Estimated Recipe Cost

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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!