Dark Knight bluebeard

Sun

Full sun; flowering and growth are weaker in shade.

Water

Water regularly during the first growing season, allowing the soil surface to dry between waterings. Once established, water during prolonged dry spells; avoid persistently wet soil.

Soil

Well-drained soil, preferably light or sandy, with average to low fertility. Tolerates a range of pH levels but struggles in wet, heavy clay, especially in winter.

Height

2-3 ft (0.6-0.9 m)

Spread

2-3 ft (0.6-0.9 m)

Flowers

Late summer to early autumn; deep violet-blue flowers in clusters along the upper stems.

Foliage

Deciduous, narrow, lightly toothed grey-green leaves with a noticeable scent when rubbed.

Growth

Moderate; produces substantial new growth each spring after pruning.

Care needed

Low

• Pollinators
• Deer resistant
• Drought tolerant
• Heat tolerant
• Low allergen
• Fragrant

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Easy

Toughness

Very tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   1.6 ft (0.5 m)

2. After 1 year

   1.8 ft (0.55 m)

3. After 2 years

   2 ft (0.6 m)

4. After 3 years

   2.1 ft (0.65 m)

5. After 5 years

   2.5 ft (0.75 m)

   full size

About 5 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Safe

Growth rate

Moderate

• Plant in full sun with free-draining soil; use a raised bed if winter drainage is poor.
• Water deeply through the first growing season, then mainly during extended drought.
• Avoid rich feeding; excess nitrogen encourages soft growth at the expense of flowers.
• Keep mulch clear of the stem bases and crown.
• In colder gardens, choose a sheltered site and leave the stems standing over winter.

Pruning. In early to mid-spring, once live buds are visible and severe frost is unlikely, cut the previous year's stems back to a low framework, usually 6-12 in (15-30 cm), just above healthy buds. Remove dead stems at the base; flowers form on the new season's growth.

Spring

Plant after severe frost has passed, choosing a sunny position with good drainage.

Early to mid-spring

Prune back to healthy low buds and remove winter-killed stems.

Late spring

Take softwood cuttings from healthy, non-flowering shoots.

Summer

Water young plants deeply during dry weather; avoid frequent shallow watering.

Late summer

Enjoy the flowers and leave flowering stems available to visiting bees.

Autumn

Leave hard pruning until spring and check that fallen leaves or mulch are not trapping moisture around the crown.

• Plant in small groups near the front or middle of a sunny border for blue flowers after many summer perennials have finished.
• Combine with ornamental grasses and coneflowers for a late-season planting with contrasting flower shapes.
• Use beside gravel paths with lavender and stonecrops, where drainage is good and the foliage softens hard edges.
• Repeat along a sunny path as a loose, low edging rather than a tightly clipped hedge.

Garden styles it suits: Cottage garden, Pollinator garden, Dry gravel garden, Low-maintenance, New perennial (prairie) and Mediterranean.

Plant it with: Lavender, Purple coneflower, Autumn stonecrop, Feather reed grass, Yarrow and Russian sage.

Wildlife: The late-season flowers provide nectar and pollen for bees and also attract butterflies and other pollinating insects.

• Root or crown rot in wet soil: improve drainage or move the plant to a raised bed; avoid winter waterlogging.
• Winter stem dieback: wait for spring buds before pruning, then remove dead wood; protect the root zone from prolonged wet conditions.
• Sparse flowers and floppy growth: provide full sun, stop high-nitrogen feeding and prune in spring.
• Capsid bugs can leave small holes and distorted young leaves: tolerate minor damage and encourage predatory insects; treatment is rarely necessary.

Not known to be toxic to people, cats, dogs or horses. No part is generally identified as poisonous, but it is not a food plant and species-specific safety information is limited; discourage pets and children from eating it.

• Longwood Blue bluebeard (Caryopteris × clandonensis 'Longwood Blue')

  Usually taller and more upright, with lighter blue flowers; 'Dark Knight' has deeper violet-blue flowers. Labels are more reliable than appearance alone when plants are not flowering.

• Russian sage (Salvia yangii)

  Usually taller and airier, with silvery stems, more divided leaves and long, open sprays of small lavender-blue flowers rather than dense clusters close to the stems.

Caryopteris comes from Greek words meaning nut and wing, referring to the winged fruits, while bluebeard describes the blue flowers with their projecting stamens.

Propagation. Take softwood cuttings in late spring or semi-ripe cuttings in summer and root them in a free-draining medium. Seedlings will not reliably retain the characteristics of 'Dark Knight'.

Accepted botanical name

Caryopteris clandonensis

Sources: GBIF (CC BY 4.0) and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.