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BeddingHerbaceous Perennial

Dahlia 'Knockout'^PBR (Sin)

dahlia 'Knockout'

A tuberous-rooted perennial to about 75cm, with very dark bronze, almost black, foliage, blooming from mid-summer until the first frosts. Single flowers have broad, lemon yellow petals, and a dark brown central disc opening to orange

Synonyms

Dahlia 'Mystic Ladies Knockout'
Dahlia 'Mystic Knockout'
see moreDahlia Mystic Sun
Dahlia Mystic Illusion

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Ultimate height

0.5–1 metres

Time to ultimate height

1–2 years

Ultimate spread

0.5–1 metres

Clay

Loam

Sand

Moisture

Moist but well–drained, Well–drained

pH

Acid, Alkaline, Neutral

	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

Full sun

Aspect

South–facing or East–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: Asteraceae
Native to GB / Ireland: No
Foliage: Deciduous
Habit: Bushy
Potentially harmful: All parts may cause severe discomfort if ingested and may irritate skin. Wear gloves and other protective equipment when handling
Genus: Dahlia are tuberous rooted perennials with pinnately divided leaves and showy flowerheads, double in many cultivars, in summer and autumn
Name status: Adopted
Horticultural Group: Single-flowered dahlias have flowerheads usually less than 10cm across, with one or two rows of spreading ray florets, surrounding a central boss of small tubular disc florets which are valuable for bees and butterflies

How to grow

Cultivation

Grow in fertile, humus-rich, well-drained soil, enriched with organic matter and general purpose fertiliser, in full sun. Pinch out growing tips to encourage bushy plants and stake (see staking perennials). Water freely in dry periods. Lift and store tubers in autumn to replant or use as a source of cuttings in spring

Propagation

Propagate by softwood cuttings taken in spring from shoots from stored tubers, or divide the tubers ensuring each division has a viable bud

Suggested planting locations and garden types

Cottage and informal garden
City and courtyard gardens
Patio and container plants
Wildlife gardens
Cut flowers
Flower borders and beds

Pruning

Deadhead to prolong flowering. Cut back to near ground level in the autumn, before lifting and storing for the winter

Pests

Leaf miners, aphids, glasshouse red spider mite and slugs are common pests. Earwigs sometimes damage blooms. Capsid bug and caterpillars are occasional pests

Diseases

Powdery mildews can be damaging in dry conditions. In wet weather grey moulds and other fungal rots can be a problem. Fungal rots can also damage stored tubers. A virus may cause stunting, leaf markings and distortion

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