- Family: Daisy Family – Compositae, subfamily Asteroideae
(formerly Aster Family – Asteraceae)
- Growing form: Annual herb.
- Height: Up to 3 m (10 feet). Stem unbranched, rough–soft-haired.
- Flower: Flowers 5–40 cm (2–15 in.) wide, single flower-like capitula surrounded by involucral bracts. Capitulum’s ray-florets yellow, tongue-like, neuter; disk florets brownish, tubular, small. Stamens 5. Gynoecium composed of 2 fused carpels. Involucral bracts in 2 rows, leafy, ovate, tapered. Capitula usually solitary, soon nodding.
- Leaves: Lower opposite, upper alternate, stalked. Blade usually broadly ovate, 10–40 cm (4–15 in.) long, at least lower down cordate based, large-toothed.
- Fruit: Long, flat-oval, slightly angular, smoothly haired–virtually glabrous achene, usually tipped with 2 withering bristles.
- Habitat: Harbours, railway yards, bird-feeding places, waste ground, rubbish tips, sometimes seashores. Also an ornamental and useful plant.
- Flowering time: August–September.
Common sunflower is native to the south-west of the USA, around the New Mexico area. As a feral plant it has probably completely disappeared due to cross-breeding, but it has spread with people all around the world. The sunflower is a versatile plant which Native Americans learned to make use of 2,000–3,000 years ago. The seeds are used in e.g. muesli, bread dough, yogurt and porridge, and they contain half their weight in healthy sunflower oil, which is used as a cooking oil and in the margarine industry. Lower grades are used in paint, linseed oil, lubricating oil and lighting.
Sunflowers can grow to astonishing heights and are a handsome addition to gardens and balconies. Their large capitula turn gracefully throughout the day, following the sun and attracting a wide range of wildlife to their abundant care. Butterflies suck their nectar, while bumblebees and honey-bees gather pollen. The flowers also attract many kinds of predatory insects, which control the numbers of aphids and other vermin in the vicinity. Sunflowers that are left to stand during the winter provide nutrition for birds that eat their seeds.
Sunflowers that grow wild in Finland usually spread from seed mixtures that are left out for birds to eat in winter. City cleaning spreads the seeds to dumps and roadsides, and the clearing away of earth, grit and snow from city streets also plays a part in transporting the seeds. Cypselas that end up in water can travel long distances; they are able to float for weeks on end. Some Finnish sunflowers have arrived straight from North America in unwashed maize and soya beans. Sunflowers in Finland do not usually have enough time for their seeds to ripen before winter sets in, so seeds must be imported every year.
Other Helianthus species
When people speak of sunflowers they are almost always referring to common sunflowers, although there are many other species. The sunflower that is most common in Finnish gardens is perennial sunflower (also known as showy sunflower, hybrid prairie sunflower, mountain sunflower, cheerful sunflower, H. x laetiflorus), an almost-native variety which is a tenacious natural hybrid of two species that can survive a long time in old gardens. One of it’s parent plants is Jerusalem artichoke (sunchoke, H. tuberosus) which is grown for its tubers and which is also a member of the sunflower genus.