Whether you know it as blue beard or blue mist, Caryopteris x clandonensis is one of the few plants that produce genuinely blue flowers. An accidental hybrid of C. incana and C. mongholica, it has since been bred to produce several popular cultivars. The compact size and soft gray foliage make blue beard plants a good choice in any size garden.
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. Small, pale blue flowers cover the plant from midsummer into fall.
|Common Name||Blue beard, blue mist, blue spirea|
|Botanical Name||Caryopteris × clandonensis|
|Plant Type||Deciduous shrub or woody perennial|
|Mature Size||2–4 ft. tall and wide|
|Soil Type||Medium moisture, well-drained|
|Soil pH||Neutral (6.5 to 7.5)|
|Bloom Time||Midsummer to early fall|
|Flower Color||Blue, purple; pink cultivars available|
|Hardiness Zones||6b-9a (USDA)|
|Native Area||Hybrid; parent species native to east Asia|
Blue Beard Care
Caryopteris is usually planted from potted nursery starts. Make sure to plant it in a hole well-prepared with compost or peat moss, and perhaps vermiculite, to improve drainage. The crown should be level with the soil surface or slightly higher. Blue beard is slow to leaf out in the spring, so don’t panic if yours looks like a dead twig. Ideally, the plant should be planted in the spring or fall, provided that your area doesn't get too cold.
Blue beard plants are low-maintenance—they tolerate both drought and shade, and they don't need much fertilizer. However, like all other plants, blue beards have their preferences, so you should plant them in full sun and with medium-moisture soil if you want them to thrive. They typically grow quickly, between 18 and 30 inches annually.
Caryopteris plants should be planted in full sun areas for the best blooms. They will tolerate some shade, although flowering will be somewhat reduced. Blue beard may bloom later in the season if they are planted in a shady location.
Caryopteris prefers a medium-moisture, well-draining soil, but does quite well in moderately arid conditions once it is well established; but it dislikes wet, poorly drained soils. Blue beard thrives best with a neutral soil pH but will accept slightly acidic or slightly alkaline conditions.
Blue beard plants are drought-tolerant, but water them regularly when young. 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 6b to 9a; however, in the northern part of the range (zone 6), it may die back to ground level in winter. This is not a problem because this is a fast-growing shrub that blooms on new growth from the current year.
These plants are not heavy feeders, so some organic matter mixed into the planting hole should be all the food they need. Side dressing with compost is preferred over chemical fertilizers for Caryopteris plants. Too much fertilizer makes for a leafy plant with fewer blooms.
Types of Blue Beard
There are several types of blue beard commonly used in landscapes:
- 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, silver-grey leaves, and a taller stature reaching about 4 feet high.
- ‘Worchester Gold’: This cultivar has golden foliage and lavender flowers.
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 plant ages, you will get some dead wood in the center. Prune this out as needed.
If the plants die back in winter, as is common in zones 6 and 7, remove the dead stalks in spring as new growth is beginning.
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. Here's how to do it:
- Use sharp pruners to cut 6-inch segments off new-growth stems.
- Remove the lower pairs of leaves and dip the ends of the cuttings in rooting hormone.
- Plant the cutting in pots filled with ordinary general-purpose potting mix.
- Keep the cuttings in bright indirect light and make sure they are well-watered until they have developed good root systems. At this point, they are ready to plant in the landscape.
How to Grow Blue Beard From Seed
Propagating these plants from seeds is not a common activity, since it's so easy to propagate them from stem cuttings. But if you want to try seed propagation, collect them from the seed pods in late fall, place them in a plastic bag filled with damp sphagnum moss, and chill them in a refrigerator for three months.
In late winter, sow the seeds 1/4-inch deep in pots filled with damp commercial potting mix. Place the pots in a bright location at about 68 degrees Fahrenheit to germinate and sprout, and continue to grow them until planting time in spring. If your growing season is long enough, your plants will probably bloom in their first growing season.
Be aware that your new seedlings may look a little different from the mother plant, which is common when planting seeds from hybrid plants.
No particular winter protection is necessary with these plants. Clear away plant debris from around the base of the plants to prevent fungi and pest larvae from overwintering. Some gardeners like to do severe pruning in early winter rather than spring.
Common Pests and Plant Diseases
Caryopteris can be bothered by the fourline plant bug. 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 only disease of concern is crown rot, a fungal disease that sometimes occurs when blue beard is planted in dense, wet soil.
How to Get Blue Beard to Bloom
Generally speaking, these plants bloom well provided they are getting enough sun. However, over-fertilizing can cause the plant to direct its energy into leaf production at the expense of flowers. If your plant is not blooming adequately, consider cutting back on whatever fertilizer or compost it is getting.
Regular deadheading of the spent flower heads will also help stimulate continue blooming.
Common Problems With Blue Beard
Blue beard is a remarkably durable, easy-care plant, with just a couple of common issues.
Branches Die Back One by One
When the branches on your plant begin to die and turn brown, it is a likely sign of crown rot—a fungal disease that affects the plant at ground level. Close examination may show brown, brittle stem sections at ground level. By the time the disease is diagnosed, it may be too late to save the plant. Crown rot is usually a problem in overly wet, dense soils, so you can prevent it by making sure to amend the soil to improve its drainage before planting. Organic matter and a few handfuls of vermiculite blended into the planting hole are good amendments if your soil is too dense.
Volunteer Plants Cover the Garden
Blue beard self-seeds itself very freely, meaning that you will be constantly plucking out volunteer seedlings. To minimize this, make sure to deadhead the spent flowers routinely, and at the end of the blooming season, trim off the stems below the flowering tips to remove any remaining seeds.
What is the best way to use blue beard in the landscape?
The compact size and soft gray foliage make blue beard plants a good choice in any size garden 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.
Are there other Caryopteris species I can try?
The C. x Clandonensis hybrid is by far the most popular form of blue beard, bred to be especially hardy. But there are several other species you may be able to find at specialty plant suppliers, including C. incana, C. divaricata, and C. nepalensis. All these plants are sold as blue beard, so review the plant labels carefully to determine which species you are buying.
How long does blue beard live?
Once established, blue beard plants will happily thrive for many years. There are known instances of plants living several decades.
How was this hybrid plant developed?
This award-winning plant was born entirely by accident. In 1930, an Englishman named Arther Simmonds attempted to propagate Caryopteris mongholica from gathered seeds. Unknown to him, a C. incana plant in the area cross-pollinated his plant, resulting in seeds that produced a brand-new hybrid that eventually became the most popular of all Carypoteris varieties.