Dahlia merckii (B)

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Merck dahlia

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Herbaceous Perennial
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A tuberous-rooted perennial to about 2m with many-branched stems and large, divided, mid-green leaves. Single flowers, in summer and autumn, may be pink, purple or white with a purple or yellow centre

Position

Full sun

Soil Types

Chalk, Clay, Loam, Sand

Max Height

1.5-2.5 metres

Max Spread

0.5-1 metres

Size

Time to Maturity
2–5 years
Max Spread
0.5-1 metres
Max Height
1.5-2.5 metres

Growing Conditions

Chalk Clay Loam Sand
Moisture
Moist but well–drained
pH
Acid or Alkaline or Neutral

Position

Full sun
Aspect
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)
H3

Colour & Scent

Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Asteraceae
Native to GB/Ireland
No
Foliage
Deciduous
Habit
Clump forming
Genus
Dahlia are tuberous rooted perennials with pinnately divided leaves and showy flowerheads, double in many cultivars, in summer and autumn
Name Status
Correct
Plant Range
Mexico

How to Grow

Cultivation

Plant tubers 10-15cm deep in fertile, humus-rich, well-drained soil, in full sun. Cut back to near ground level in mid-autumn. In mild areas, and on well-drained soils, leave the tubers in the ground and protect with a deep, organic mulch. In colder areas, or on heavy soils, lift and store the tubers and replant in late spring after all danger of frost has passed. See dahlia cultivation and our video How to plant dahlia tubers and care tips

Propagation

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

Suggested planting locations and garden types

  • Cottage and informal garden
  • Wildlife gardens
  • Flower borders and beds
  • Cut flowers
  • Wall side borders

Pruning

Deadhead to prolong flowering

Pests

May be susceptible to aphids, capsid bug, earwigs, caterpillars, slugs, glasshouse red spider mite and onion thrips

Diseases

May be susceptible to powdery mildews, dahlia mosaic virus, cucumber mosaic virus, tomato spotted wilt virus, storage rots, leafy gall, crown gall, dahlia smut, grey moulds, fungal leaf spot, phytophthora, sclerotinia and verticillium wilts