Astilbe × arendsii 'Koblenz' — Clump-forming, upright plumes above a mound of foliage

Overview

Astilbe × arendsii 'Koblenz' is a clump-forming, upright plumes above a mound of foliage perennial in the genus Astilbe, part of the Saxifragaceae family, with deciduous; deeply divided and toothed, often bronze-tinted when young foliage. Astilbe × arendsii 'Koblenz' grows best in partial shade; full sun only where the soil stays reliably wet, and tolerates fertile loam or clay enriched with organic matter soils and neutral to slightly acid pH. Its UK hardiness is rated H7. Suggested uses include shade gardens, woodland borders, moist perennial beds and alongside ponds or streams..

About

Astilbe × arendsii 'Koblenz' is a clump-forming perennial producing upright flower plumes above a mound of deeply divided, toothed, deciduous leaves that are often bronze-tinted when young. It flowers from June to August. The plant suits reliably moist, sheltered positions in partial shade. It will not tolerate drought.

About the genus

Astilbe is a genus of 18 species of rhizomatous flowering plants within the family Saxifragaceae, native to mountain ravines and woodlands in Asia and North America. Some species are known by the common names false goat's beard and false spirea.

Wikipedia contributors, "Astilbe", CC BY-SA 4.0 — Astilbe

In the garden

Astilbe × arendsii 'Koblenz' belongs to the Saxifragaceae and sits within the Astilbe group of clump-forming perennials. It carries erect, feathery flower plumes above a mound of deeply divided, toothed foliage; new leaves commonly show a bronze tint before greening. Flowering runs from June to August. Sit it in partial shade, or in full sun only where soil remains reliably wet. It prefers fertile loam or clay enriched with organic matter and a neutral to slightly acid pH. Soil must be kept reliably moist to boggy — the cultivar will not tolerate periods of drought — and choose a sheltered, north-, east- or west-facing aspect to reduce drying winds. Its UK hardiness rating H7 means it is fully hardy in British gardens when sited correctly. Use 'Koblenz' in shade borders, woodland edges, moist perennial beds or beside ponds and streams where moisture is constant. Allow the foliage to form a compact mound beneath the flower spikes so the plumes sit clearly above the leaves; avoid exposed, drying sites if you want the upright flowers to hold through the summer months.

Growing conditions

Best soil and position for Astilbe

Sunlight: Partial shade; full sun only where the soil stays reliably wet
Soil type: Fertile loam or clay enriched with organic matter
Soil pH: Neutral to slightly acid
Soil moisture: Reliably moist to boggy; will not tolerate drought
Aspect: North, east or west facing
Exposure: Sheltered
UK hardiness: H7

Plant details

Astilbe × arendsii 'Koblenz' size, habit and characteristics

Plant type: Perennial
Habit: Clump-forming, upright plumes above a mound of foliage
Foliage: Deciduous; deeply divided and toothed, often bronze-tinted when young
Suggested uses: Shade gardens, woodland borders, moist perennial beds, alongside ponds or streams.

Care notes

Pruning and caring for Astilbe × arendsii 'Koblenz'

Cultivation: Moisture is everything - an astilbe that dries out scorches at the leaf margins and the plumes shrivel before they open. Plant in ground improved with plenty of organic matter, mulch generously each spring, and site out of hot afternoon sun unless the soil is genuinely wet. They are excellent in the damp shade where little else thrives.
Pruning: No pruning needed. Leave the spent plumes standing for winter structure and cut the whole clump down in late winter before new growth begins.
Propagation: Divide congested crowns in early spring; the woody rootstock may need a spade or a saw. Species can be raised from seed but cultivars will not come true.
Pest resistance: Largely trouble-free, though vine weevil grubs attack the roots of container plants.
Disease resistance: Healthy in suitable conditions. Powdery mildew appears on plants under drought stress, which is a symptom of the wrong site rather than of disease pressure.

Frequently asked questions

How do I grow Astilbe × arendsii 'Koblenz'?

Moisture is everything - an astilbe that dries out scorches at the leaf margins and the plumes shrivel before they open. Plant in ground improved with plenty of organic matter, mulch generously each spring, and site out of hot afternoon sun unless the soil is genuinely wet. They are excellent in the damp shade where little else thrives.

Where is the best place to plant Astilbe × arendsii 'Koblenz'?

Astilbe × arendsii 'Koblenz' prefers partial shade; full sun only where the soil stays reliably wet. It suits sheltered positions.

What soil does Astilbe × arendsii 'Koblenz' need?

Astilbe × arendsii 'Koblenz' grows best in fertile loam or clay enriched with organic matter soil. It prefers neutral to slightly acid soil. Aim for soil that stays reliably moist to boggy; will not tolerate drought.

How do I prune Astilbe × arendsii 'Koblenz'?

No pruning needed. Leave the spent plumes standing for winter structure and cut the whole clump down in late winter before new growth begins.

Is Astilbe × arendsii 'Koblenz' hardy in the UK?

Astilbe × arendsii 'Koblenz' has an RHS hardiness rating of H7, meaning it is fully hardy throughout the UK, tolerating temperatures below -20°C.

How do I propagate Astilbe × arendsii 'Koblenz'?

Divide congested crowns in early spring; the woody rootstock may need a spade or a saw. Species can be raised from seed but cultivars will not come true.

More in the Astilbe genus

Browse all Astilbe →