Buddleja davidii 'Harlequin' arrived in cultivation in 1964 as a spontaneous mutation of 'Royal Red,' and for a time its lance-shaped leaves edged in creamy white gave it a distinct identity among flowering shrubs. Growing 4 to 6 feet tall with the characteristic arching habit of the davidii species, it offers small, fragrant, reddish-purple flowers arranged in dense cylindrical panicles that attract both bees and butterflies from summer onward. Like all davidii cultivars it blooms on new wood, making early-spring pruning — cutting to about a foot from the ground — both safe and beneficial, encouraging a more compact habit and larger flower production.

The variegation is 'Harlequin's' defining feature and also its principal vulnerability. Under stress — drought, pest pressure, or simply poor siting — the plant has a persistent tendency to revert branches back to solid green foliage, and vigilance in removing those plain-leaved shoots is necessary to maintain the intended effect. Spider mite susceptibility adds to the maintenance picture, particularly in dry summers. It remains widely available, and for gardeners who want a butterfly bush with genuine foliage interest through the full season, it still makes a reasonable case for itself. Other variegated forms including 'Notbud,' 'Thia,' and 'White Harlequin' offer similar aesthetics and may suit specific garden schemes.