Bicolor Butterfly Bush Varieties and Similar Cultivars Compared
Butterfly bush comes in far more flavors than most gardeners realize. The bicolor form stands out with its two-tone pink and purple flower spikes, but nurseries also carry solid-color cultivars that may be a better fit for your space or design goals. This guide cuts through the options so you can pick the right one.
Bicolor vs. Solid-Color: What Is the Difference?
Bicolor butterfly bush (Buddleja davidii, Bicolor form) produces flower spikes in a two-tone mix, typically combining pink or rose tones with lavender or purple hues. The exact color combination varies by seed strain or grower, since "Bicolor" as sold is often a trade name rather than one fixed patented cultivar.
Solid-color cultivars breed true from cuttings or come from controlled breeding lines. Each named variety locks in its color, size, and bloom intensity, making them predictable from nursery tag to mature plant. Solid colors include deep purples, true pinks, red-toned forms, and even blue-lavender shades.
The real choice is not bicolor versus solid, but rather: Do you want the unpredictability of a seed strain (bicolor), or the guaranteed color and habit of a named cultivar?
Comparison Table: Major Butterfly Bush Varieties
| Variety | Bloom Color | Mature Height | Growth Rate | Key Traits | Best For |
|---|---|---|---|---|---|
| Bicolor Butterfly Bush | Pink/rose + purple/lavender mix | 5-8 ft | 2-3 ft/year | Variable exact tone; seed strain; sweet fragrance | Mixed borders; cottage gardens; pollinator zones |
| 'Black Knight' | Deep purple | 5-8 ft | 2-3 ft/year | Darkest cultivar available; long spikes; vigorous | Formal gardens; focal points; high-contrast designs |
| 'Pink Delight' | Soft pink | 5-8 ft | 2-3 ft/year | True pink without purple undertones; fragrant | Romantic plantings; pastel schemes; fragrance gardens |
| 'Royal Red' | Deep red-purple | 5-8 ft | 2-3 ft/year | Richest warm tones; bold statement blooms | Warm-color palettes; dramatic borders; sunset gardens |
| 'Nanho Blue' | Blue-lavender | 5-8 ft | 2-3 ft/year | Rarest hue; more restrained growth than standard | Cool-color schemes; complementary purple foliage |
| Lo & Behold Series | Variable (pink, purple, red) | 3-4 ft | Slower than standard | Dwarf; more sterile (less seed drop); compact habit | Containers; small gardens; foreground; low maintenance |
Bicolor Butterfly Bush: The Seed Strain Option
The bicolor form as commonly sold is a seed-grown trade line, not a single registered cultivar. This means two plants labeled "Bicolor" from different nurseries may show slightly different color ratios. One might lean more pink, another more lavender.
If you like that natural variation and don't mind minor surprises, bicolor offers charm at a lower price point than named cultivars. The two-tone effect creates visual interest without matching a specific design brief.
Pros: Affordably priced; classic two-tone effect; widely available; sweet honey-like fragrance on warm days.
Cons: Color tone unpredictable across growers; treated as generic trade name; exact bloom intensity varies by seed lot; not registered as one stable cultivar.
Best for: Gardeners who embrace variation; pollinator gardens where color matters less than nectar and pollen; mixed cottage borders where "unexpected" is a feature, not a bug.
'Black Knight': Deepest Purple Option
'Black Knight' is the darkest butterfly bush cultivar available. Its deep, almost midnight-purple spikes stand out even from across the garden.
Pros: Unmatched color depth; produces long, full flower spikes; vigorous, predictable growth; proven cultivar widely stocked by nurseries.
Cons: Can look heavy or somber in soft, pastel plantings; may need more deadheading to maintain shape due to vigor; deep color can recede visually in shade.
Best for: Formal gardens; dramatic focal points; high-contrast color schemes; gardeners who want a strong purple without any pink undertones.
'Pink Delight': True Pink Without Purple Undertones
'Pink Delight' offers clean, true pink blooms without the lavender or magenta cast that many butterfly bush cultivars carry. The color stays consistent from early season through fall.
Pros: Pure pink tone; reliable color; long bloom season; fragrant; pairs naturally with whites, soft yellows, and cool pastels.
Cons: True pink can fade in intense heat; slightly less vigorous than some other cultivars (still fast growing, but slightly more compact); less widely available than 'Black Knight'.
Best for: Romantic or cottage-style gardens; paired with roses and delphiniums; pink-focused color schemes; gardeners seeking fragrance in a specific hue.
'Royal Red': Warm, Deep Tones
'Royal Red' bridges red and purple, offering rich, warm tones that read as burgundy or wine-dark depending on light conditions.
Pros: Unique warm undertones; bold presence in the garden; works with both warm and cool color palettes; full-sized growth habit.
Cons: Can appear brownish-red in certain soils or lighting; less common than 'Black Knight' or bicolor forms; warm tones may dominate adjacent pastels.
Best for: Sunset-themed gardens; warm-color borders with golden foliage companions; creating drama without pure darkness; gardeners seeking red without sacrificing butterfly bush form.
'Nanho Blue': The Rare Cultivar
'Nanho Blue' is the rarest butterfly bush color in the standard-sized range, offering blue-lavender flower spikes. It is less vigorous than 'Black Knight' and creates a more restrained, sculptural habit.
Pros: Unique blue-lavender hue rarely seen in butterfly bush; more controlled growth than many cultivars; works with cool-color and complementary purple-foliage schemes; excellent for pollinator gardens.
Cons: Harder to source; slower growth means more years to reach full size; blue undertones can fade in intense afternoon sun; less fragrant than some pink cultivars.
Best for: Cool-color gardens; pairing with blue flowers and gray foliage; gardeners hunting for a rare cultivar; creating subtle rather than bold garden statements.
Lo & Behold Series: Dwarf and Container-Friendly
Lo & Behold is a modern breeding line of dwarf butterfly bush cultivars available in pink, purple, and red. These plants reach 3 to 4 feet rather than the standard 5 to 8 feet, and they produce fewer viable seeds (more sterile), reducing unwanted self-seeding.
Pros: Compact; ideal for containers and small spaces; slower growth means less frequent pruning; more sterile genetics reduce invasion concern where Buddleja is regulated; multiple colors available within the series.
Cons: Smaller blooms and shorter spikes than full-size cultivars; higher per-plant cost as a specialty series; still need full sun and good drainage; still require annual hard pruning for best bloom.
Best for: Container gardeners; small yards; foreground borders; anyone seeking a butterfly bush without overwhelming size; regions where butterfly bush self-seeding is regulated or invasive.
Which Variety Should You Choose?
Start with your space. Do you have room for a 5- to 8-foot shrub, or do you need dwarf genetics? Then match your color scheme.
Solid-color cultivars let you commit to a palette: choose 'Pink Delight' for romance, 'Black Knight' for drama, or 'Royal Red' for warmth. Bicolor offers flexibility and cottage-garden charm at a lower cost, accepting slight variation as part of its appeal.
For planting and care guidance, all these varieties follow the same cultural rules: full sun (6 or more hours), well-drained soil, moderate water at establishment, then drought tolerance once established. Prune hard in late winter to about 12 to 18 inches from the ground, and deadhead spent flower spikes through the season to encourage rebloom and control seed drop.
Quick Reference: Cultivar Selection Checklist
- Want true pink: Choose 'Pink Delight'
- Want deepest purple: Choose 'Black Knight'
- Want warm, red-toned blooms: Choose 'Royal Red'
- Want rare blue-lavender: Choose 'Nanho Blue'
- Want two-tone color mix: Choose Bicolor Butterfly Bush seed strain
- Want compact, container-friendly: Choose Lo & Behold Series
- Want lower seed drop in restricted regions: Choose Lo & Behold Series or confirm cultivar sterility
- Want affordably priced option: Choose Bicolor or check for local cultivar stock
- Want proven, widely available option: Choose 'Black Knight'
- Want color that pairs easily with other plantings: Choose based on your palette (pink with pastels, deep purple with dark foliage, red-purple with warm golds)