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Herbaceous Perennial

× Heucherella 'Onyx'

heucherella 'Onyx'

A clump-forming, semi-evergreen perennial, to around 25cm high, with lobed, glossy dark purple leaves that appear almost black. Slender stems bear clusters of tiny, bell-shaped white flowers in early summer

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Ultimate height

0.1–0.5 metres

Time to ultimate height

2–5 years

Ultimate spread

0.5–1 metres

Clay

Loam

Sand

Moisture

Moist but well–drained

pH

Acid, Neutral

	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

Full sun
Partial shade
Full shade

Aspect

East–facing or North–facing or South–facing or West–facing

Exposure

Sheltered

Hardiness
Hardiness ratings
All ratings refer to the UK growing conditions unless otherwise stated. Minimum temperature ranges (in degrees C) are shown in brackets
H1a: under glass all year (>15C)
H1b: can be grown outside in the summer (10 - 15)
H1c: can be grown outside in the summer (5 - 10)
H2: tolerant of low temperatures, but not surviving being frozen (1 to 5)
H3: hardy in coastal and relatively mild parts of the UK (-5 to 1)
H4: hardy through most of the UK (-10 to -5)
H5: hardy in most places throughout the UK even in severe winters (-15 to -10)
H6: hardy in all of UK and northern Europe (-20 to -15)
H7: hardy in the severest European continental climates (< -20)

Botanical details

Family: Saxifragaceae
Native to GB / Ireland: No
Foliage: Semi evergreen
Habit: Clump forming
Genus: × Heucherella are hybrids between Heuchera and Tiarella, and are evergreen, clump-forming perennials with ovate or rounded leaves and open panicles of small bell-shaped pink or white flowers over a long period
Name status: Unresolved

How to grow

Cultivation

Thrives in fertile, moist but well-drained soil in dappled or afternoon shade, or in full sun if the soil is reliably moist. Mulch annually, and divide every few years to prevent the rhizomes rising to the surface

Propagation

Propagate by division. Lift the plant once in spring growth, taking small vigorous sections from around the edge. Each section should have good roots and 2-3 shoots

Suggested planting locations and garden types

Cottage and informal garden
Patio and container plants
Flower borders and beds
Garden edging
Ground cover
Underplanting of roses and shrubs

Pruning

No pruning required, but old leaves and flower stems may be removed to improve appearance

Pests

May be susceptible to vine weevil, especially when grown in containers

Diseases

Generally disease-free

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