About
Helianthus giganteus, the giant sunflower, is a clump-forming, tuberous perennial up to 2.5 m tall with narrow, coarse, dark-green leaves. Clusters of small, bright-yellow daisy-like flowerheads with dark-yellow centres are produced on dark reddish to green stems in late summer and early autumn. A bold and imposing perennial for the back of a sunny border.
About the genus
Helianthus, the sunflowers, are tall, erect annuals and tuberous or rhizomatous perennials with coarse, simple, rough-textured leaves and large, showy, daisy-like flowerheads in yellow, orange or occasionally red tones. Excellent for the back of a sunny border and important plants for pollinators.
Growing conditions
SunlightFull sun, Partial shade
Soil typeChalk, Loam, Sand, Clay
Soil pHNeutral, Alkaline
Soil moistureMoist but well-drained, Well-drained
AspectSouth-facing, West-facing
ExposureSheltered
UK hardinessH4
Plant details
Plant typeHerbaceous Perennial
HabitSpreading branched, Clump forming
FoliageDeciduous
Height2.5-4 metres
Spread1-1.5 metres
Time to full height1-2 years
Suggested usesCottage and informal garden, Wildlife gardens, Coastal, Wildflower meadow, Prairie planting
Care notes
CultivationGrow in a moderately fertile, humus-rich, moist, well-drained, neutral to alkaline soil in full sun. May need support. See staking perennials
PruningDeadhead to prolong flowering
PropagationPropagate 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
Pest resistanceMay be susceptible to slugs and snails
Disease resistanceMay be susceptible to Powdery mildews and sclerotinia diseases