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Herbaceous Perennial

Helianthus giganteus

giant sunflower

A clump-forming perennial, up to 2.5m in height, with narrow, coarse green leaves and small flowers in late summer and early autumn, with dark yellow centres and yellow ray florets on dark reddish to green stems

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Size
Ultimate height
2.5–4 metres
Time to ultimate height
1–2 years
Ultimate spread
1–1.5 metres
Growing conditions
Chalk
Loam
Sand
Clay
Moisture
Moist but well–drained, Well–drained
pH
Neutral, Alkaline
Colour & scent
StemFlowerFoliageFruit
Spring Green Red Green
Summer Green Red Yellow Green
Autumn Green Red Yellow Green
Winter
Position
  • Full sun
  • Partial shade
Aspect

South–facing or West–facing

Exposure
Sheltered
Hardiness
H4
Botanical details
Family
Asteraceae
Native to the UK
No
Foliage
Deciduous
Habit
Clump forming
Genus

Helianthus can be tall, erect annuals, tuberous or rhizomatous perennials, with coarse simple leaves and large daisy-like flower-heads

Name status

Correct

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How to grow

Cultivation

Grow in a moderately fertile, humus-rich, moist, well-drained, neutral to alkaline soil in full sun. May need support. See staking: perennials

Propagation

Propagate by seed sown in-situ, or in pots or modules, in spring

Suggested planting locations and garden types
  • Cottage and informal garden
  • Wildlife gardens
  • Coastal
  • Wildflower meadow
  • Prairie planting
  • Cut flowers
  • Flower borders and beds
  • Wall side borders
Pruning

Deadhead to prolong flowering

Pests

May be susceptible to slugs and snails

Diseases

May be susceptible to Powdery mildews and sclerotinia diseases

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