Bishop of Llandaff Dahlia

Overview

The Bishop of Llandaff Dahlia (Dahlia 'Bishop of Llandaff') is a heritage cultivar prized for the striking contrast between its dark, near-black bronze-purple foliage and its glowing scarlet-red flowers. Unlike the big blowsy dinnerplate dahlias, it carries open, single to semi-double peony-form blooms that let pollinators reach the golden centre. It is one of the most recognisable and enduring dahlias in the trade and holds the RHS Award of Garden Merit.

Origin & Background

The genus Dahlia is native to the uplands of Mexico and parts of Central America, where the wild species grow in seasonally dry, sunny conditions. 'Bishop of Llandaff' is a garden hybrid, generally credited to the Welsh nurseryman Fred Treseder of Cardiff and introduced in the mid-1920s. It was named for the Bishop of Llandaff (a district of Cardiff) and went on to found a whole informal "Bishop" series of dark-leaved, single-flowered dahlias.

Appearance

The foliage is the defining feature: deeply cut, fern-like leaves in a dark bronze-maroon that reads as near-black in strong light. Against this sit flat, open flowers of intense scarlet-red, roughly 8 to 10 cm across, single to semi-double with a small ring of central florets showing yellow anthers. Mature height is typically 90 to 110 cm (about 3 to 3.5 ft) with a spread of 45 to 60 cm. The dark leaf colour is strongest in full sun and holds through the season, while the blooms open from midsummer and continue in flushes until the first hard frost blackens the top growth.

Why People Grow It - Qualities & Benefits

• Bold, long-season colour contrast that few other border plants match
• Open flower form is genuinely useful to bees and hoverflies, unlike double dahlias
• Long bloom window from midsummer right up to frost, especially if deadheaded
• Excellent cut flower and a strong structural accent in mixed borders and large containers

Care

Light: Full sun is best; it needs at least six hours of direct light for the darkest foliage and heaviest flowering. Water: Moderate to high through the growing season; keep the soil evenly moist but never waterlogged, watering deeply in dry spells once tubers are established. Soil: Fertile, humus-rich, moisture-retentive but free-draining soil, ideally slightly acidic to neutral (pH about 6.0 to 7.0). Hardiness: USDA zones 8 to 11 where tubers can overwinter in the ground; in zones 3 to 7 it is grown as a lifted tender perennial. Bloom or Season: Midsummer to first frost, roughly July to October, with repeat flushes over several months. Extra: Tall stems flower heavily and may need discreet staking. Note: dahlias are mildly toxic to cats and dogs, so site or supervise plantings where pets browse.

Planting & Propagation

Plant dormant tubers outdoors after the last frost, setting them 10 to 15 cm deep with the old stem base pointing up, spaced about 45 to 60 cm apart. In cold zones, start tubers under cover a few weeks early for a longer season. Named cultivars like this one do not come true from seed, so propagate by lifting and dividing the tuber clumps in autumn or spring (each division needs an intact "eye" at the crown), or by taking basal cuttings from sprouting tubers in late winter. In frost-prone areas, lift the tubers after the first frost, dry them, and store them cool, dark and frost-free over winter.

Common Problems & Pests

• Slugs and snails shred young shoots and can strip emerging plants overnight
• Aphids, capsid bugs, earwigs and spider mites disfigure buds and foliage
• Powdery mildew and tuber or crown rot in soggy, poorly drained soil, plus frost damage to unlifted tubers in cold zones

Toxicity & Safety

Dahlias, including 'Bishop of Llandaff', are considered mildly toxic to cats and dogs. Ingestion of the leaves, stems or tubers typically causes mild gastrointestinal upset such as drooling, vomiting or mild diarrhoea, and contact with the sap can cause mild skin irritation or dermatitis in sensitive animals and people. Reactions are usually mild and self-limiting, but keep pets from chewing the plant and wear gloves if you are prone to skin irritation; contact a vet if a pet eats a large amount or symptoms persist.

Pros & Cons

Pros

• Dramatic dark foliage and vivid flowers give unusually long-lasting colour
• Pollinator-friendly open blooms and reliable, well-known garden performance

Cons

• Tubers need lifting and frost-free storage in colder zones, adding annual work
• Tall stems can flop and need staking, and slugs love the fresh growth

Best Suited For

• Sunny mixed borders and cottage-garden schemes wanting a bold focal plant
• Gardeners who want cut flowers and pollinator support and do not mind autumn tuber care

FAQ

Do I have to dig up the tubers every winter?

Only in colder regions. In USDA zones 8 to 11 tubers can usually stay in the ground with a protective mulch, but in zones 3 to 7 you should lift, dry and store them frost-free, then replant after the last frost.

Why are the leaves so dark and will they stay that way?

The near-black bronze foliage is a genetic trait of this cultivar, and it holds all season. The colour is deepest in full sun; in too much shade the leaves green up and flowering drops off.