Bluebeard 'Dark Knight'
Caryopteris x clandonensis 'Dark Knight' · Lamiaceae
Whorls of deep, dark blue flowers up every stem in late summer, over scented, silvery-grey leaves. The darkest of the bluebeards.
- Size
- 3 ft tall, 3 ft wide
- Zones
- 5 to 9
- Light
- Full sun
- Flowers
- Early August to mid September
- Pets
- No toxicity recorded
- Job in a bed
- Drift
A bed built around bluebeard 'Dark Knight'
The planner designed this bed around bluebeard 'Dark Knight' when this page was made: a 12 × 6 ft (3.7 × 1.8 m) English border in zone 6, full sun. It chose the other plants from the 715 that suit those conditions and its dry soil, and says below why bluebeard 'Dark Knight' stands where it does.
The plants
- 1 Bluebeard 'Dark Knight' × 1, blue
- 2 Blue fescue × 7, blue-green leaves
- 3 Basket-of-gold × 11, yellow
- 4 Tatarian aster 'Jindai' × 3, purple
- 5 Sideoats grama × 3, purple
- 6 Yarrow × 3, pink
- 7 Schubert's allium × 3, pink
- 8 Spring starflower × 12, white
Why this plant
- The only blue.
- Part of the bed's structure. Shrubs and grasses keep their shape when the perennials die down. So do blue fescue and sideoats grama.
Why here
- Anchors a back corner. At 3 ft it is one of the taller plants here, and the tallest close the ends of the bed, where they stand in front of nothing.
- A step in the back row. Next to sideoats grama (2½ ft): no two neighbours there are the same height, so the back steps up and down like a skyline.
- One plant, alone. A shrub is seen as an object, and needs clear ground around it.
Why now
- In flower for 7 weeks. From early August to mid September.
- Fills a gap. For four of those weeks nothing else on the plan is in flower.
Planned as an English border: 7 of the 7 groups (100%) are drifts, longer along the bed than they are deep. Blue fescue stands beside Schubert's allium, a proven pairing. Something is in flower for 30 weeks, from early April to early November.
The planner's own design check: 13 Excellent, 3 Good, 1 Satisfactory. It flags one thing to watch: Nothing on this plan is highly poisonous or an aggressive spreader.
Open this bed in the planner Change its size, the sun or the style, move plants about, or swap one for another.
Where bluebeard 'Dark Knight' goes in a border
At 3 ft it belongs in the middle of a bed. In the planner's ten height classes it is medium tall (2½ to 3 ft).
Its job: drift. Planted in a small group of three or five, and repeated further along in the other number.
True blue in late August, when the garden is mostly yellow. Bees cover it. Cut it back hard each spring, like a perennial, and give it sharp drainage.
- Dark blue for late summer
- Bees and butterflies
- Dry, sunny borders
What to plant with bluebeard 'Dark Knight'
Plants recorded as good partners for it, and what each pairing does:
- Sedum 'Autumn Joy': in flower together for six weeks, from mid August; bold leaves against its fine ones; happy in the same dry soil.
- Black-eyed Susan: purple against yellow, opposite each other on the colour wheel, in flower together for seven weeks.
- Little bluestem: its blue-green leaves are a setting for the flowers, before and after; happy in the same dry soil.
Questions about bluebeard 'Dark Knight'
Does bluebeard 'Dark Knight' need sun or shade?
Bluebeard 'Dark Knight' grows in full sun (6 or more hours of direct sun a day).
It wants dry, sharply drained soil, on the lean side, with no feeding, and little watering once settled. Once settled in, it stands drought.
What zones does bluebeard 'Dark Knight' grow in?
USDA zones 5 to 9. It is hardy to zone 5, which means it survives winter nights down to about −10 °F (−23 °C).
Gardening in Canada? Use the USDA zone for your town: Canada's own zone map uses different numbers.
When does bluebeard 'Dark Knight' flower in my zone?
In zone 5 it flowers early August to mid September. As a summer flower it moves about half a week for every zone: earlier where it is warmer.
| Zone 5 | Early August to mid September |
|---|---|
| Zone 6 | Early August to mid September |
| Zone 7 | Early August to mid September |
| Zone 8 | Early August to mid September |
| Zone 9 | Late July to mid September |
Worked out from Hopkins' bioclimatic law: spring arrives about four days later for each degree of latitude north, and one zone is roughly two degrees. A warm spring or a cold one moves any garden two weeks either way.
How far apart should bluebeard 'Dark Knight' be planted?
2½ ft (75 cm) apart, from the middle of one plant to the middle of the next. That is a little closer than its full width of 3 ft (90 cm), so a group knits into one patch.
It grows 3 ft (90 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.
How many bluebeard 'Dark Knight' plants do I need?
At 2½ ft apart, set out in staggered rows:
- 2 to fill 10 square feet (about 1 m²)
- 5 for a single row 10 ft (3 m) long
- 6 to fill a 4 × 8 ft bed on its own
In a mixed border, plant it as a group of three or five, with a second group further along in the other number.
In the bed above, the planner used one in one group.
Is bluebeard 'Dark Knight' poisonous to dogs and cats?
No toxicity is recorded for dogs, cats, horses or people, according to NC State Extension.
"Not toxic" is not "edible": a pet that eats a lot of any plant can be sick.
Is there a native plant like bluebeard 'Dark Knight'?
Bluebeard 'Dark Knight' is not native to North America. These North American natives come closest to doing its job:
- Shrubby cinquefoil 'Abbotswood': the same job in a bed; 6 in shorter, 6 in wider.
- Aromatic aster 'Raydon's Favorite': the same job in a bed, the same size and the same colour; flowers mid September to early November.
- Ironweed 'Iron Butterfly': the same job in a bed and the same flowering time; 6 in narrower, purple, not blue.
Matched the way the planner's Swap button matches plants: the same job in a bed, then size, then flowering time.
Do deer eat bluebeard 'Dark Knight'?
Mostly not. NC State lists it as resistant to deer. No plant is proof against a hungry deer in a hard winter, but this one is low on the menu.
What flowers after bluebeard 'Dark Knight'?
Bluebeard 'Dark Knight' is over by mid September. These start as it finishes and carry the same spot on, so it never goes flat:
- Garden chrysanthemum: from mid September to late October, 24 in tall, to stand in front of it and cover its fading stems.
- Montauk daisy: from mid September to late October, 3 ft tall.
- October daphne: from mid September to late October, 8 in tall, to stand in front of it and cover its fading stems.
What does bluebeard 'Dark Knight' look like in winter?
Bluebeard 'Dark Knight' drops its leaves and stands as bare branches. That is when to see its shape, and to prune it if it needs pruning.
Is bluebeard 'Dark Knight' good for bees and butterflies?
Bluebeard 'Dark Knight' is visited by butterflies.
More Caryopteris
- Bluebeard Caryopteris x clandonensis
In these guides
- Pet-safe plants for a sunny border
- Plants for butterflies
- Shrubs under 4 feet for small gardens
- Plants with blue flowers
- Silver and grey-leaved plants
Every fact on record
- Type
- Shrub
- Size
- 3 ft (90 cm) tall, 3 ft (90 cm) wide
- Plant
- 2½ ft (75 cm) apart
- Height class
- Medium tall (2½ to 3 ft)
- Place in the bed
- Middle
- Flowers
- Early August to mid September; dense clusters; blue, purple
- Leaves
- Fine texture, deciduous; grey-green
- Shape
- Mounding, clumping
- Hardy in
- USDA zones 5 to 9
- Light
- Full sun
- Soil
- Lean, dry and sharply drained
- Water
- Low
- Feeding
- None needed
- Family
- Lamiaceae
- Attracts
- Butterflies
- Stands up to
- Deer, drought
Checked against NC State Extension. Flowering times are for zone 5: later in colder zones, earlier in warmer ones. Toxicity and spread information is a general gardening guide, not veterinary or medical advice, and invasive status varies by region. If a person or pet eats a plant, contact poison control or a vet. Check your local invasive species list before planting anything with a spread warning.