How to grow Helianthus
From the Greek helios, the sun, anthos, a flower. (Compositae). Sunflower. A genus of tall, coarse-growing plants, annuals and perennials, gross feeders which dominate the border in which they are planted. H. annuus, the common sunflower, is a plant of some economic importance, as the seeds are fed to fowl and produce an edible obi', and the flowers yield a yellow dye.
Perennial species cultivated H atrorubens (syn. H. sparsifolius), 6-8 feet, golden-yellow, September, 'The Monarch, with flowers 6 inches across is a good cultivar. H. decapetalus, 4-6 feet, tough, sharply toothed leaves, sulphur-yellow flowers, August to October. Cultivars include 'Capenoch Star', lemon yellow, single, good for cutting; 'Capenoch Supreme', large, single, pure yellow 'Loddon Gold', double, rich yellow; 'Soleil d'Or', double, sulphur-yellow, quilled petals. H. laetiflorus (syn. H. rigidus), 5-7 feet, yellow, September and October. 'Miss Mellish', orange-yellow, is the best cultivar of this, but both are very rampant plants. H. salicifolius (syn. H. orgyalis), 6 feet, small yellow flowers, September and October,
willow-like leaves. H. tuberosus, Jerusalem artichoke, 6-8 feet, yellow, October. Cultivation The best plants are grown in a stiff loam in full sun. Seeds of annual kinds can be sown in situ in April. To get the largest flowerheads, water and give liquid feeds occasionally up to flowering time. The perennials can be divided in autumn or spring. H. laetiflorus needs constant checking to prevent it from dominating the surrounding area and is best planted in rough corners where it will provide useful flowers for cutting.