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Annual Biennial

Helianthus annuus 'American Giant'

sunflower 'American Giant'

A vigorous, erect annual growing to 4.5m tall, with oval to heart-shaped, hairy, toothed, mid-dark green leaves. Sturdy stems bear large, bright yellow flower heads in Summer followed by edible seeds

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Ultimate height

4–8 metres

Time to ultimate height

1 year

Ultimate spread

0.1–0.5 metres

Chalk

Clay

Loam

Moisture

Moist but well–drained

pH

Alkaline, Neutral

	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

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)

Botanical details

Family: Asteraceae
Native to GB / Ireland: No
Foliage: Deciduous
Habit: Columnar upright
Genus: Helianthus can be tall, erect annuals, tuberous or rhizomatous perennials, with coarse simple leaves and large daisy-like flower-heads
Name status: Unresolved

How to grow

Cultivation

Sow seeds in humus-rich, moist but free-draining soil in full sun in Spring. Alternatively, seeds can be sown indoors, three weeks before the last frost, in modules then planted out.

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
Wildlife gardens
Cut flowers
Flower borders and beds

Pruning

Cut back after flowering

Pests

May be susceptible to slugs and snails

Diseases

May be susceptible to powdery mildew, sclerotinia diseases

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Helianthus annuus 'American Giant'

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