Whether you know it as blue beard or blue mist, Caryopteris x clandonensis is one of the few plants that produce genuinely blue flowers. This plant originated as an accidental hybrid of C. incana and C. mongholica and has since been bred to produce several popular cultivars. Depending on the climate, these plants are grown either as deciduous shrubs or woody perennials that die back to the ground each winter. Growing from neat low mounds, the narrow silvery-gray leaves resemble those of willow.
The flowers are what gives the plant its common names. The blue or purplish blooms, appearing are mid-to-late summer, are clustered in panicles above the foliage in small feathery puffs.
|Botanical Name||Caryopteris × clandonensis|
|Common Names||Blue beard, blue mist|
|Plant Type||Deciduous shrub or woody perennial|
|Mature Size||2 to 4 feet tall with a similar spread|
|Sun Exposure||Full sun|
|Soil Type||Medium moisture, well-drained soil|
|Soil pH||6.5 to 7.5 (slightly acidic to slightly alkaline)|
|Bloom Time||Mid-to-late summer|
|Flower Color||Blue, purple; pink cultivars available|
|Hardiness Zones||5 to 9 (USDA)|
|Native Area||Parent species are native to East Asia|
How to Grow Blue Beard Plants
Blue beard plants will do best when planted in well-drained soil in a sunny location. Plant them at the same level or slightly higher than they were in the nursery container. Other than spring pruning, this is a very carefree plant.
Caryopteris plants should be sited in full sun for best blooms; they will tolerate some shade, although flowering will be somewhat reduced. Blue beard may bloom later in the season when they are planted in a shady location.
Caryopteris prefers a medium-moisture, well-draining soil, though it tolerates fairly moist soil. They thrive best with a neutral soil pH, but will accept slightly acidic or slightly alkaline conditions.
Water blue beard plants regularly when young, but once established, they don’t require any supplemental watering unless you are having a particularly dry season.
Temperature and Humidity
Blue beard is reliably hardy in USDA zones 5 to 9, but in the northern part of the range (zones 5 and 6) it may die back to ground level in winter. This is not a problem, since this is a fast-growing shrub that blooms on new growth from the current year.
These plants are not heavy feeders and some organic matter mixed into the planting hole should be all the food they need. Side dressing with compost is preferred over fertilizing Caryopteris plants. Too much fertilizer makes for a leafy plant with fewer blooms.
Pruning Blue Beard
To keep the plant shaped and flowering, Caryopteris plants should be cut down by at least half in the early spring. You can cut them back to 12 to 18 inches without harm. As the plants age, you will get some dead wood in the center. Prune this out as needed. If the plants die back in winter, remove the dead stalks in spring as new growth is beginning.
Blue beard is slow to leaf out in the spring, so don’t panic if yours looks like a dead twig. Be patient.
Propagating Blue Beard Plants
Blue beard may self seed, and the volunteers can be transplanted as you wish.
You can also propagate by soft-wood cuttings in late spring. Cut 6-inch segments off new-growth stems, then remove the lower pairs of leaves. Dip the ends of the cuttings in rooting hormone, then plant them in potting mix. Keep the cuttings in bright indirect light and make sure they are well-watered until they have developed good root systems.
Varieties of Blue Beard
- Caryopteris x clandonensis : The original hybrid is one of the hardiest forms available and still one of the most popular.
- 'Dark Knight': This variety has the darkest blue flowers, but it is a bit more temperamental to grow.
- 'Sunshine Blue': This cultivar has deep blue flowers offset by yellow foliage.
- ‘Pink Chablis’: This Proven Winners introduction has pink flowers.
- ‘Longwood Blue’: This variety has sky-blue fragrant blooms and has a taller stature—about 4 feet tall.
- ‘Worchester Gold’: This cultivar has golden foliage and lavender flowers.
Common Pests/ Diseases
Caryopteris can be bothered by the four-line plant bug in June, The foliage will get mottled, but it doesn’t harm the plant and the bug moves on quickly enough. If the bugs disturb you, insecticidal soap, horticultural oil, or neem oil will control them.
The compact size and soft gray foliage make blue beard plants a good choice in any size garden. This is a versatile plant, equally at home in perennial borders, shrub borders, or as a small hedge plant. It is very effective planted in mass and is highly valued for its late summer flowers when few other shrubs are blooming.
The blue flowers mix particularly well with either pastels and whites or vibrant yellows. Since they bloom later in the summer, Caryopteris is a nice companion for Rudbeckia and goldenrod. They’ll blend equally well with the soft colors of pink phlox and pink or white Buddleia.
Caryopteris should be included in every butterfly garden. Bees, butterflies, and hummingbirds love it. It is extremely drought tolerant and bothered by few pests.