Coral bells 'Obsidian'

Sun

Partial shade is best, particularly afternoon shade in hot climates. It tolerates more sun in cool regions if the soil stays evenly moist.

Water

Keep evenly moist while establishing; once established, water during dry spells. Avoid saturated soil, especially in winter.

Soil

Humus-rich, well-drained soil, from slightly acidic to slightly alkaline. Heavy clay needs improved drainage or a raised planting position.

Height

0.75-1 ft (0.23-0.3 m) in leaf; 1.5-2 ft (0.45-0.6 m) in flower

Spread

1-1.5 ft (0.3-0.45 m)

Flowers

Small cream flowers on slender stems in late spring and early summer.

Foliage

Evergreen. Rounded, shallowly lobed, glossy leaves in deep purple-black, with purplish undersides; forms a compact mound.

Growth

Moderate

Care needed

Low

• Pollinators
• Cold hardy
• Low allergen

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

Difficulty

Easy

Toughness

Fairly tough

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

1. Planting day

   0.9 ft (0.27 m)

   full size

About 3 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 with the crown at soil level, not buried.
• Water at the base when the upper soil starts to dry; containers need more frequent checks.
• Apply a thin layer of compost in spring, keeping it clear of the crown.
• Use a modest slow-release feed in containers in spring; avoid heavy feeding in borders.
• Divide every three to four years if the centre becomes woody or the crown rises above the soil.

Pruning. In early spring, remove dead or badly weathered leaves without cutting into the crown. Cut spent flower stems back to their base after flowering.

Early spring

Remove damaged leaves and check for crowns lifted by frost; gently firm or replant them at the correct depth.

Spring

Plant or divide clumps and apply a thin compost mulch, leaving the crown exposed.

Late spring

Check container plants for vine weevil damage if they wilt despite moist soil.

Summer

Water during dry weather and provide afternoon shade where heat scorches the leaves.

Late summer

Remove spent flower stems, leaving healthy foliage intact.

Late autumn

Clear wet fallen leaves from the crown and check that pots and planting areas drain freely.

• Edge a partly shaded path with repeated dark mounds for a clear, low border.
• Pair with lime-green hostas or golden grasses for strong foliage contrast.
• Use in containers with ferns and small shade-tolerant perennials, ensuring good drainage.
• Plant beneath deciduous shrubs where filtered light shows off the glossy foliage without exposing it to hot afternoon sun.

Garden styles it suits: Woodland, Modern, Modern courtyard, Cottage garden, Small-space and Blues and silvers.

Plant it with: Hostas, Japanese painted fern, Japanese forest grass, Brunnera, Hellebores and Foamflower.

Wildlife: The small flowers can provide nectar and pollen for bees and other visiting insects. Its main garden value is foliage rather than a large floral display.

• Vine weevil larvae eat roots, especially in pots, causing sudden wilting or loose crowns. Inspect roots and use locally approved biological controls when conditions suit.
• Crown rot develops in wet soil or when planted too deeply. Improve drainage, keep the crown exposed and remove badly rotted plants.
• Leaf scorch causes crisp brown patches in hot sun or dry soil. Provide afternoon shade and water consistently.
• Frost heave can lift shallow crowns out of the ground. Check after winter and replant at the original depth once the soil is workable.

Not known to be toxic to cats, dogs, horses or people; no part is recognised as seriously poisonous. It is an ornamental plant, not intended for eating.

• Coral bells 'Palace Purple' (Heuchera 'Palace Purple')

  Usually has more bronze-purple, less uniformly black foliage and more angular leaves; colour varies with growing conditions.

• Coral bells 'Black Pearl' (Heuchera 'Black Pearl')

  Also nearly black, but typically has more strongly ruffled, scalloped leaf edges; 'Obsidian' has a smoother outline.

• Foamflower (Tiarella cordifolia)

  Usually has green leaves with dark markings rather than uniformly purple-black leaves, and produces conspicuous fluffy flower spikes.

Heuchera honours the German physician and botanist Johann Heinrich von Heucher, while 'Obsidian' refers to the cultivar's dark, glossy leaves resembling black volcanic glass.

Propagation. Divide healthy clumps in spring, retaining rooted sections with sound growing points. Seed-grown plants will not reliably retain the colour and form of 'Obsidian'.

Accepted botanical name

Heuchera

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