Helianthus 'Double Whammy' (d)

RHS Plant Profile

sunflower 'Double Whammy'

RHS / Joanna Kossak

Herbaceous Perennial

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A clump-forming perennial to around 90m tall with rich green, ovate leaves.Double golden-yellow flowers up to 15cm across are borne from summer into autumn and comprise a ring of elliptic ray florets surrounding a central mound of tubular disc florets

Position

Full sun

Soil Types

Chalk, Clay, Loam

Max Height

0.5-1 metres

Max Spread

0.1-0.5 metres

Size

Time to Maturity: 2–5 years
Max Spread: 0.1-0.5 metres
Max Height: 0.5-1 metres

Growing Conditions

Chalk Clay Loam

Moisture: Moist but well–drained
pH: Alkaline or Neutral

Position

Full sun

Aspect: East–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): H5

Colour & Scent

Season	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family: Asteraceae
Native to GB/Ireland: No
Foliage: Deciduous
Habit: Columnar upright
Genus: Helianthus can be tall, erect annuals, tuberous or rhizomatous perennials, with coarse simple leaves and large daisy-like flower-heads
Name Status: Accepted

How to Grow

Cultivation

Grow in a moderately fertile, humus-rich, moist but well-drained, neutral to alkaline soil in full sun. Needs a long hot summer to flower well. May need support

Propagation

Propagate by seed or division. Divide established clumps every 2-4 years to both increase plants and retain vigour. See sowing seeds indoors for further advice

Suggested planting locations and garden types

Cottage and informal garden
Prairie planting
Wildlife gardens
Patio and container plants
Flower borders and beds
Cut flowers
Wall side borders

Pruning

Cut back after flowering

Pests

May be susceptible to slugs and snails

Diseases

May be susceptible to powdery mildews and Sclerotinia diseases