Caryopteris x clandonensis 'Kew Blue' (Kew Blue Spiraea)


Michael's Opinion

Not a true Spiraea, Caryopteris is a marginally hardy shrub best planted en masse and will produce a mass of fine blue blooms in August. In flower it gives the appearance of Spiraea hence the reference to the common name.

Botanical Information

FamilyVerbenaceae (Lamiaceae)
GenusCaryopteris
Speciesx clandonensis
Cultivar'Kew Blue'
CategoryWoody
TypeShrub (deciduous)
OriginA selection from the Royal Botanic Gardens, Kew, Great Britain.
Pronunciation

Details

USDA Hardiness Zone6 - 9
USDA Hardiness Ref.
Canadian Hardiness Zone5a
Canada Hardiness Ref.
RHS Hardiness ZoneH7 - H3
RHS Hardiness Ref.
Temperature (°C)(-21)˚ - (-1)˚
Temperature (°F)(-5)˚ - 30˚
Height75 cm
Spread75 cm
GrowthFast
Flowering PeriodAugust

Description and Growing Information

General DescriptionA mounded almost herbaceous shrub. Flowers attract humming birds and are ideal for chalk.
ID CharacteristicBlue Flowers in August with silvery grey foliage.
ShapeMounded.
LandscapeMakes a lovely garden shrub, best planted en masse.
PropagationSoftwood cuttings root easily and should be removed from mist as soon a rooting is sufficient. Can be transplated easily as roots are sparse and stringy.
CultivationWell drained, loose soil and a sunny location. May experience winter dieback in excessively cold winters. Requires a minor haircut in spring once the new shoots have fully emerged.
Notable SpecimensThe Gardens of Fanshawe College, London, Ontario, Canada.
Leaf DescriptionOpposite, simple, ovate 2.5-5 cm long, acute, rounded and scented.
Flower DescriptionDark blue and scented, produced on new growth.
Colour DescriptionDull blue-green with silvery underside.
Texture DescriptionMedium.

Photographs