Helianthus maximiliani

RHS Plant Profile

Maximilian sunflower

Synonyms

Coreopsis maximiliani

Herbaceous Perennial

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A clump-forming herbaceous perennial with green hairy stems, long lance-shaped leaves and fragrant, yellow daisy-like flowers borne all the way up the length of each stem

Position

Full sun

Soil Types

Chalk, Clay, Loam, Sand

Max Height

1.5-2.5 metres

Max Spread

1-1.5 metres

Size

Time to Maturity: 1 year
Max Spread: 1-1.5 metres
Max Height: 1.5-2.5 metres

Growing Conditions

Chalk Clay Loam Sand

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

Position

Full sun

Aspect: West–facing or South–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): H4

Colour & Scent

Fragrance Flower

Season	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family: Asteraceae
Native to GB/Ireland: 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
Plant Range: N America (MO, TX, S. Canada)

How to Grow

Cultivation

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

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
Cottage and informal garden
Wildflower meadow
Wildlife gardens
Prairie planting
Low Maintenance
Flower borders and beds
Cut flowers
Wall side borders

Pruning

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

Pests

May be susceptible to slugs and snails

Diseases

May be susceptible to powdery mildews and sclerotinia diseases