Helianthus × multiflorus

RHS Plant Profile
thin-leaved sunflower

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thin-leaved sunflower visionspictures.com
thin-leaved sunflower visionspictures.com
Annual Biennial

A clump-forming perennial species of sunflower to around 180cm in height with coarse, hairy, dark green leaves. Single or double almost dahlia-like golden yellow flowers with domed centres appear on multiple long, rigid stems throughout the summer

Position

Full sun

Soil Types

Chalk, Clay, Loam

Max Height

1.5-2.5 metres

Max Spread

0.5-1 metres

Size

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

Growing Conditions

Chalk Clay Loam
Moisture
Moist but well–drained
pH
Acid or 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)
H2

Colour & Scent

Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Asteraceae
Native to GB/Ireland
No
Foliage
Deciduous
Habit
Bushy, 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

How to Grow

Cultivation

Grow in moderately fertile, neutral to alkaline, humus-rich, moist but well-drained soil in full sun. This plant was included in the RHS Helianthus (sunflower) trial 2024 https://www.rhs.org.uk/plants/trials-awards/plant-trial-results/fleuroselect-sunflowers

Propagation

Propagate by seed (sown indoors) between April and May and keep in a sunny location, planting out in late spring or early summer when the risk of frost has passed. Also propagate by seed (sown outdoors) when the risk of frost has passed

Suggested planting locations and garden types

  • City and courtyard gardens
  • Cottage and informal garden
  • Wildlife gardens
  • Flower borders and beds

Pruning

Cut back to the ground in autumn or leave for birds to eat the seeds

Pests

May be susceptible to slugs and snails

Diseases

May be susceptible to powdery mildews and sclerotinia diseases