Culture
Easily grown in average, medium moisture, well-drained soil in full sun. Prefers loose loams. Tolerates some drought. Intolerant of wet, poorly-drained soils. Roots are winter hardy to USDA Zone 5, but top growth is only reliably winter hardy to USDA Zone 7. Thus, stems will often die to the ground in the cold winters of Zones 5 and 6, with roots surviving to push up new stems in spring. Many gardeners in Zones 5 and 6 simply assume stems will be damaged in winter and automatically prune back hard all stems each year in early spring. Moreover, even in warm winter climates where the stems usually survive winter, gardeners still frequently prune the plants back hard in early spring to promote vigorous new stem growth. Flowering is unaffected by spring pruning because plants bloom on new growth.
Noteworthy Characteristics
Caryopteris × clandonensis, commonly called bluebeard, blue spirea or blue mist, is a low-mounded, deciduous shrub that is valued for its aromatic foliage and late summer flowers which are said to resemble clouds of blue smoke or mist. This hybrid was discovered in cultivation as an accidental cross between C. incana and C. mongholica. Clandonensis hybrids typically produce about 18-30” of growth per year, so total shrub height (usually from 2-3’) depends in large part upon the extent of winter dieback and/or the annual spring pruning. Flowers are very attractive to butterflies, bees and other beneficial insects. Foliage is aromatic when brushed with a hand.
Genus name comes from Greek karyon meaning "nut" and pteron meaning "wing" in reference to the winged fruits found on this shrub.
'Longwood blue' is a taller cultivar which may reach a height of 4'. It features a profuse, shrub-covering bloom of fragrant, violet-blue flowers in terminal and axillary clusters (cymes) from late summer into fall. Ovate to lance-shaped, silvery-gray leaves (to 1.5" long). A selection from Longwood Gardens in Pennsylvania.
Problems
No serious insect or disease problems. Crowns may rot in wet, poorly-drained soils.
Uses
Perennial borders. Shrub borders. Very effective in large groups or massed. Also effective as a low hedge. Valued for its late summer to fall flowers when few other shrubs are in bloom.