Helianthus 脳 laetiflorus

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RHS Plant Profile

showy sunflower

Other common names

perennial sunflower, prairie sunflower, rough-leaved sunflower, stiff sunflower

Synonyms

Helianthus rigidus misapplied
Helianthus scaberrimus

Herbaceous Perennial

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A rhizomatous, clump-forming perennial to 2m tall with dark green, narrowly-ovate and toothed leaves. Bright yellow flowerheads with dark centres,10-12cm in diameter, are borne from late summer into autumn

Position

Full sun

Soil Types

Chalk, Loam, Sand

Max Height

1.5-2.5 metres

Max Spread

1-1.5 metres

Size

Time to Maturity: 2鈥�5 years
Max Spread: 1-1.5 metres
Max Height: 1.5-2.5 metres

Growing Conditions

Chalk Loam Sand

Moisture: Moist but well鈥揹rained
pH: Alkaline or Neutral

Position

Full sun

Aspect: South鈥揻acing or West鈥揻acing or East鈥揻acing
Exposure: Exposed or 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: Bushy
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

Requires a moderately fertile, moist but well-drained, alkaline to neutral soil in full sun

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

City and courtyard gardens
Coastal
Cottage and informal garden
Wildlife gardens
Cut flowers
Flower borders and beds

Pruning

Cut back old stems after flowering as they die down for the winter

Pests

Susceptible to slugs

Diseases

Powdery mildews and sclerotinia diseases may be a problem