Sunflower

Profile

Family

Asteraceae

Habit

annual

Height

2.5 m

Spread

0.8 m

Growth

very fast

Lifespan

1 year

First yield

after 1 year

Hardiness

zone 7–9

Shade tolerance

partial shade

Soil

Sand, Silt, Loam

Soil moisture

dry – very moist

pH

5.9 – 8.1

Flowering & harvest

Times apply to the northern hemisphere in a temperate climate and shift with altitude and cultivar.

Uses

Edible: Sunflower seeds – raw or cooked. They have a delicious, nutty flavour but are difficult to harvest because of their small size. Specialised machines are available commercially. The fat-rich kernels can be ground into a powder, processed into sunflower butter, or used for sunflower yoghurt. Mixed with cereal flour they make a nutritious bread. In Russia cultivars with an oil content of up to 50% have been developed. The oil contains 44–72% linoleic acid. Sprouted seeds are best for sunflower yoghurt; they are puréed with water and fermented. The sprouted seeds can be eaten raw. A nutritional analysis of the seeds is available. Young flower buds – steamed and served like artichokes. They have a mild and pleasant flavour, but are somewhat laborious to harvest. The average yield is 900–1575 kg/ha, but yields above 3375 kg/ha have also been reported. From the seeds, a high-quality semi-drying edible oil is obtained. It is low in cholesterol and is said to rival olive oil in quality. It is used in salads, margarine or for cooking. The roasted seeds serve as a substitute for coffee and drinking chocolate. According to another report, the roasted seed husks are also used. The leaf stalks are cooked and mixed into other foods.

Other uses: From the seeds an edible, semi-drying oil is obtained. Some cultivars contain up to 45% oil. This oil, often mixed with a drying oil such as linseed oil (Linum usitatissimum), is used for the production of soap, candles, varnishes, paints etc. as well as for lighting purposes. It is regarded as an unsurpassed lubricant. From the seed capsules blotting paper is made. From the inner stem high-quality writing paper is obtained. The pith of the stems, with a density of 0.028, is one of the lightest substances known. It has many uses, for example for the manufacture of life jackets and microscope slides. The dried stems are an excellent fuel; the ash is rich in potash. Both the dried stems and the empty seed capsules are excellent for kindling. From the fibres of the stem, paper and fine fabrics are produced. From the flowers a yellow dye is obtained. From the seeds of certain cultivars grown by the Hopi Indians of southwest North America, a purple-black dye is obtained. Sunflowers are suitable as green manure in spring and yield a good quantity of plant material. Root secretions of the plant can inhibit the growth of neighbouring plants.

Growing

Sunflowers are easy to grow and thrive in most soils, including nutrient-poor ones, provided they are deep and well drained. They grow best, however, in deep, nutrient-rich soils. They tolerate neither acid nor waterlogged conditions. Particularly when grown for their edible seeds, they prefer a sunny position, but tolerate light shade. They require a neutral or, preferably, chalky soil. Since sunflowers have a very efficient root system, they can also be grown in areas that are too dry for many other crops. Established plants are quite drought-tolerant, except during flowering. Sunflowers tolerate an annual rainfall of 20–400 cm, a mean annual temperature between 6 and 28°C and a pH between 4.5 and 8.7. The young shoots are extremely attractive to slugs; the plants can be completely destroyed by them. Sunflowers are rarely if ever browsed by deer or rabbits. The sunflower is a very decorative plant, often grown in gardens and, owing to its edible seeds and many other uses, also an important crop. It grows well in Britain, but its seeds do not ripen reliably there, which is why it is currently not suitable for commercial cultivation. It is the state flower of Kansas. Three different groups of sunflowers are cultivated: Giant cultivars reach a height of 1.8 to 4.2 metres and have flower heads 30 to 50 cm in diameter. The seeds are large, white or grey, sometimes with black stripes, and best suited for cooking, although their oil content is lower than that of other cultivars. Examples of this type are 'Grey Stripe', 'Hopi Black Dye', 'Mammoth Russian' and 'Sundak'. Semi-dwarf cultivars reach a height of 1.3 to 1.8 metres, ripen early and have flower heads 17 to 23 cm in diameter. The seeds are smaller, black, grey or striped, and their oil content is higher. Examples of these are the cultivars 'Pole Star' and 'Jupiter'. Dwarf cultivars reach a height of 0.6 to 1.4 m, ripen early and have flower heads 14 to 16 cm in diameter. Some cultivars are bred for higher cold tolerance and should grow more reliably in Britain. The plants tend to grow better in the south and south-west of England. Most cultivars require a frost-free growing season of four months, although some Russian cultivars are harvestable after only 70 days. At cooler latitudes the seeds contain a higher proportion of polyunsaturated fatty acids. The plant has a strong taproot that can penetrate up to 3 metres deep into the soil, and a widespread, branched root system. Sunflowers get along poorly with potatoes but thrive with cucumbers and corn. Since they are very vigorous and lush, they can inhibit the growth of neighbouring plants. If sunflowers are grown too frequently at the same site, they tend to deplete the soil. This plant is a good bee magnet and yields plenty of nectar. Its flowers attract beneficial insects such as lacewings and parasitic wasps. These prey on various insect pests, especially aphids.

Propagation

Sowing – sow in spring directly outdoors. Alternatively you can sow 2–3 seeds per pot in spring in the greenhouse. Use a nutrient-rich potting compost. Thin the seedlings to the strongest one, feed them occasionally with liquid fertiliser to prevent nutrient deficiency, and plant out in late spring or early summer. Seed harvested and stored at a moisture content of 12% retains its germination capacity for several years.

Origin & habitat

Western North America. Occasional escapes from British gardens.

Open, dry or moderately moist soils on the plains.

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