‘Dark Knight’

It’s not often that we run across a plant that evokes a true visceral reaction. We appreciate beauty, we’re impressed by a colorful display, and we may even recall treasured moments when a particular scent triggers that certain something. But a plant that elicits a take-your-breath-away moment can be rare.

Name: Caryopteris ×

clandonensis ‘Dark Knight’
Common name: Dark Knight bluebeard; blue mist shrub
Hardiness: Zones 5 to 9
Mature height: Up to 4 feet
Mature spread: Up to 4 feet
Classification: Deciduous shrub
Landscape use: Mid-border or mixed perennial garden; outstanding focal point; containers
Ornamental characteristics: Casually rounded to rangy habit with slender, mottled stems that flush purple with new growth; narrow, dull green to gray- or blue-green leaves flash silvery beneath; foliage slightly aromatic when brushed; profuse, deep, cobalt-blue flowers in clusters cover the plant in late summer into fall. Exceptional, traffic-stopping color. Flowers fade to gray-green, then dry to tan if allowed to remain over winter.

‘Dark Knight’ caryopteris is one such gem. Alternately called caryopteris, bluebeard or blue mist shrub (or even blue spirea), this small shrub first caught my eye from an office window on the 21st floor. Even at that distance, the cobalt blue flowers stood out among the acres of urban farmer’s market offerings on Daley Plaza in Chicago, dominating the brilliant cockscombs, zinnias and thousands of mums. Never has the elevator to the ground floor been so slow! Because I commuted by train, I purchased only two plants and ignored the indignant glare of fellow commuters.

Caryopteris is one of those unusual shrubs that straddles classifications and hardiness zones. Older growth is woody and has a pleasing, somewhat mottled gray appearance on slender but sturdy stems. New growth, however, is nearly herbaceous and stems appear smooth with a purple cast. So the top growth is reliably hardy to Zone 7 and the root structure is winter hardy to Zone 5. In colder climes, caryopteris benefits from a hard pruning – I cut mine to six inches or so – and the crew cut encourages blooms on the tender new growth. When those blooms appear in late summer, they’ll stop traffic.

The striking and unusual flowers attract all manner of winged guests, including butterflies and a few adventurous hummingbirds. Even beneficial bugs love them, and they’re bothered by few pests. (Deer appear not to be impressed.) Because I was unable to decide upon the perfect sunny spot to plant my first selections, I toted the pots back and forth between the front yard and the back. While the intense blue flowers bobbed and weaved along the walk, they also seemed to hum. It took a few trips to discover the source of the happy sound: The plants were alive with bees, far too drunk to bother with me.

In the meantime, the weather turned sharply cold, discouraging any last-minute attempts at gardening. So these brave little shrubs languished in their pots until I gave up hope and tucked them away in the garage, where they remained, sans light or water, until spring. How determined are these plants? After months of neglect, they bravely sprouted tiny, tentative gray-blue foliage and I introduced them slowly to a sunny side yard, where they thrived.

And where they created more plants. Softwood cuttings usually yield a reliable crop, but caryopteris is a prolific bloomer and the dried flower heads produce abundant seed. Leave the spent stems for winter interest, and you’ll be rewarded with numerous young ones. As long as you supply average, well-drained soil and a sunny location, caryopteris is happy to perform. Don’t want “volunteers”? The rather stringy root system allows you to pluck easily, and transplanted seedlings are quick to take.


COURTESY OF SALLY BENSON

Grouped in threes or used as a single focal point, ‘Dark Knight’ can’t help but stand out. While the shrub is adding growth throughout the early months, it’s a pleasant filler. Then, just as other blooming shrubs and perennials are settling down, this caryopteris virtually explodes with rich, regal color, demanding the attention it deserves.

There are several lovely cultivars of Caryopteris × clandonensis, many of which provide that flash of blue you’re looking for. But give ‘Dark Knight’ a try. It’s a delightful plant to punctuate the season.

Sally Benson
Editorial Director, Horticulture Group
American Nurseryman
sbenson@mooserivermedia.com