Helianthus annuus
Annual Sunflower
Asteraceae
July to October
It is scattered throughout the country but is less
common in the North.
See the BSBI distribution map for Sunflower
It is a neophyte which has been grown in the UK since
the 1590s in gardens and allotments and in fields as
a crop. It has been known in the wild since the early
1900s.
It grows as an escape on waste ground, rubbish tips
and by roads.
Sunflower is a tall, eye-catching annual, growing
up to 3m. Flowerheads can reach 30cm across.
Flowers are in large numbers on a discoid receptical
or capitulum. Outer, ray flowers have golden yellow
ligules with 5 terminal teeth. Disc disc flowers are
tubular and brownish yellow.
Ray flowers may be male, female or bisexual. Disc
flowers are bisexual..
There is a single branched style with a yellow linear
stigma.
There are 5 stamens with fused anthers.
Each flower has 5 triangular scales.
The fruits are achenes.
There are 2 rows of large, herbacious, green, pointed
phyllaries.
Leaves are heart-shaped, and up to 40cm. Usually,
lower leaves are opposite and upper leaves alternate.
Stems and leaves are roughly hairy.
It is grown as a crop for the oil-bearing seeds.
As an escape or casual, it is on the increase.
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Next page: Sweet Chestnut
Sunflowers, Dorset
Ligulate ray and tubular disc flowers
Close-up of flowers - 2 linear stigmas
and 5 stamens with fused anthers
and stamens
Close-up of flowers - 5 triangular scales
Seed head
Close-up of seeds
Flowerhead with 2 rows of phyllaries,
rough hairy stem
Alternate leaves
Opposite leaves
Upper leaf surface
Lower leaf surface
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