Culture
Easily grown in average, medium moisture, well-drained soils 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. As a result, 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. In areas north of USDA Zone 7, many gardeners avoid dealing with winter hardiness problems by regularly pruning stems back hard in late winter to early spring each year (as is often done with buddlejas or crepe myrtles). Even in warm winter climates where the stems usually will 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 incana, commonly known as common bluebeard or blue spiraea, is a deciduous shrub that typically grows to 3-5’ tall. It is native to China and Japan. Coarsely-toothed, ovate to oblong-ovate leaves (to 3” long) are dull green above but grayish-tomentose beneath. Violet blue flowers (to 1/4” long) bloom from late summer into fall in dense cymes extending from the upper leaf axils. Flowers, leaves and stems are aromatic. Flowers are very attractive to butterflies, bees and other beneficial insects.
Genus name comes from Greek karyon meaning "nut" and pteron meaning "wing" in reference to the winged fruits found on this shrub.
Specific epithet from Latin means hoary or gray in reference to its downy gray-green leaves.
'Blue Myth’ is a compact cultivar that typically grows to 2-2 1/2’ tall. Fragrant dark blue flowers bloom from late summer to early autumn (August-October).
Problems
No serious insect or disease problems. Crowns may rot in wet, poorly-drained soils.
Uses
Perennial borders. Shrub borders. Butterfly garden. 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. Compact form suggests use in containers.