Common Name: Sunflower

General Information

Helianthus annuus is a vigorous, erect, usually unbranched annual plant that can grow from 1 - 3 metres or more tall according to the variety. It usually produces a single, large flower head at the top of the stem.
Sunflower is a major commercial crop, grown widely in the tropical to warm temperate zones for its edible, oil-rich seed. The plant also has a very wide range of other, mainly local, uses including a source of medicines, fibre, dyestuff, green manure[, ]. A very ornamental plant, it is widely grown in gardens in temperate to tropical areas of the world[].

Known Hazards

The growing plant can accumulate nitrates, especially when fed on artificial fertilizers[].
The pollen or plant extracts may cause allergic reactions[].

Botanical References

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Range

Widely distributed throughout N. America. An occasional garden escape in Britain.

Habitat

Open dry or moderately moist soils on the plains[].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Annual
Height	3.00 m
Growth Rate	Fast
Pollinators	Bees, Flies
Self-fertile	Yes
Cultivation Status	Cultivated, Ornamental, Wild

Cultivation Details

Helianthus annuus is cultivated from the temperate zone through to the tropics, though most commonly in the subtropics and warm temperate zones. They can be grown at elevations up to 2,600 metres in the tropics, but are generally better below 1,500 metres and do not thrive in humid areas[, ]. When plants are grown in cooler latitudes the seed contains higher proportions of polyunsaturated fatty oils[]. They grow best in areas where annual daytime temperatures are within the range 17 - 34°c, but can tolerate 5 - 45°c[]. They prefer a mean annual rainfall in the range 600 - 1,000mm, but tolerate 300 - 1,600mm[].
An easily grown plant, it succeeds in most soils[, , ], including poor soils provided they are deep and well-drained[], but it grows best in a deep rich soil[, ]. Plants are intolerant of acid or waterlogged conditions[]. Especially when grown for its edible seed, the plant prefers a sunny position[, , , ] though it also tolerates light shade[]. Requires a neutral or preferably calcareous soil[]. Succeeds in soils with a pH in the range of 4.5 - 8.7[]. As sunflowers have highly efficient root systems, they can be grown in areas which are too dry for many other crops[]. Established plants are quite drought-resistant except during flowering[, ].
The growth cycle is usually about 120 days, but it ranges from 75 - 180 days depending on the environment and genotype. Sowing to seedling emergence takes 5 - 10 days, emergence to floral initiation 15 - 20days, floral initiation to first flowering 20 - 90 days, flowering 5 - 15 days and flowering to seed maturity 30 - 45 days[].
The plant is ready for harvesting when the heads have turned yellow-brown and seed moisture content is 10 - 12%, about 120 - 160 days after planting for tall, and 80 - 110 days for short cultivars[].
World average seed yield is 1.2 tonnes per hectare, though higher yields of 2 - 4 tonnes (1 - 2 tonnes of oil) are obtained in Europe and the United States from modern hybrid cultivars and maximum seed yields of 5 - 6 tonnes have been obtained in field experiments[].
Pronounced heliotropism is a characteristic of sunflowers. The young heads and leaves face east in the morning and follow the movement of the sun to face west in the evening. This heliotropism decreases gradually during flowering with most mature heads eventually facing east[].
Sunflower is allogamous with a rather complex system of sporophytic self-incompatibility. However, artificial self-pollination generally results in some degree of seed set and certain genotypes show a high degree of natural self-fertility[].
The young growth is extremely attractive to slugs, plants can be totally destroyed by them[].
Members of this genus are rarely if ever troubled by browsing deer or rabbits[].
Three distinct groups of sunflowers are cultivated:-
Giant types grow from 1.8 - 4.2 metres tall with flower heads 30 - 50cm in diameter. The seeds are large, white or gray in colour, sometimes with black stripes, and are the best for culinary purposes, though the oil content is lower than for other types. 'Grey Stripe', 'Hopi Black Dye', 'Mammoth Russian' and 'Sundak' are examples of this type[, , ].
Semi-dwarf types grow from 1.3 - 1.8 m tall, are early maturing and have heads 17 - 23 cm diameter. The seeds are smaller, black, gray or striped, the oil content is also higher. Examples include 'Pole Star' and 'Jupiter'
Dwarf types grow from 0.6 - 1.4 m tall, are early maturing and have heads 14 - 16 cm in diameter[269. The seeds are small but the oil content is the highest. Examples include 'Advance' and 'Sunset'[].
The plant has a strong taproot that can penetrate the soil to depth of 3 metres, it also has a large lateral spread of surface roots[].
Sunflowers grow badly with potatoes but they do well with cucumbers and corn[, , ].
A very greedy and vigorous plant, it can inhibit the growth of nearby plants[]. Plants tend to impoverish the soil if they are grown too often in the same place[].
A good bee plant, providing large quantities of nectar[, , ]. The flowers attract beneficial insects such as lacewings and parasitic wasps[]. These prey on various insect pests, especially aphis[].

Edible Uses

Seed - raw or cooked[, , , , ]. A delicious nut-like flavour, but very fiddly to extract due to the small size of the seed. Commercially there are machines designed to do this. Rich in fats, the seed can be ground into a powder[], made into sunflower butter or used to make seed yoghurt. When mixed with cereal flours, it makes a nutritious bread[]. Cultivars with up to 50% oil have been developed in Russia[]. The oil contains between 44 - 72% linoleic acid[]. The germinated seed is said to be best for seed yoghurt, it is blended with water and left to ferment[]. The sprouted seed can be eaten raw[]. A nutritional analysis of the seed is available[].

Young flower buds - steamed and served like globe artichokes[, , , , ]. A mild and pleasant enough flavour, but rather fiddly[]. Average yields range from 900 - 1,575 kg/ha of seed, however yields of over 3,375 kg/ha have been reported[].

A high quality edible semi-drying oil is obtained from the seed[]. It is low in cholesterol[], and is said to be equal in quality to olive oil[]. Used in salads, margarines, or in cooking[, , , , , , , ].

The roasted seed is a coffee and drinking chocolate substitute[, , , ]. Another report says the roasted hulls are used[].

The leaf petioles are boiled and mixed in with other foodstuffs[].

Medicinal

A tea made from the leaves is astringent, diuretic and expectorant, it is used in the treatment of high fevers[]. The crushed leaves are used as a poultice on sores, swellings, snakebites and spider bites[, ]. The leaves are harvested as the plant comes into flower and are dried for later use[].

A tea made from the flowers is used in the treatment of malaria and lung ailments[, ].

The flowering head and seeds are febrifuge, nutritive and stomachic[]. The seed is also considered to be diuretic and expectorant[, , ]. It has been used with success in the treatment of many pulmonary complaints[].

A decoction of the roots has been used as a warm wash on rheumatic aches and pains[].

Agroforestry Uses:

Sunflowers can be grown as a spring-sown green manure, they produce a good bulk of material[].
Smallholders often intercrop sunflower with groundnut, pulses and millets, plant it on banks around irrigated fields, or use it as living supports for beans and gourds[].
Root secretions from the plant can inhibit the growth of nearby plants[].

Other Uses

An edible semi-drying oil is obtained from the seed. Some varieties contain up to 45% oil[]. The oil is also used, often mixed with a drying oil such as linseed (Linum usitatissimum) to make soap, candles, varnishes, paint etc, as well as for lighting. The oil is said to be unrivalled as a lubricant[, , , , , ].
The oil obtained from the seeds is used as an ingredient in commercial cosmetic preparations as an emollient, opacifyer and skin conditioner[].

A blotting paper is made from the seed receptacles[, , , ].

A high quality writing paper is made from the inner stalk[, , , ].

The pith of the stems is one of the lightest substances known, having a specific gravity of 0.028[]. It has a wide range of applications, being used for purposes such as making life-saving appliances and slides for microscopes[, , ].

The dried stems make an excellent fuel, the ash is rich in potassium[]. Both the dried stems and the empty seed receptacles are an excellent kindling[].

A fibre from the stem is used to make paper[] and a fine quality cloth[, , ].

A yellow dye is obtained from the flowers[, , , ].
A purple-black dye is obtained from the seed of certain varieties that were grown by the Hopi Indians of S.W. North America[, ].

Propagation

Seed - sow in situ. Germination takes 5 - 10 days[].
Seeds show a dormancy for the first 30 - 50 days after harvesting, but this is easily overcome by rinsing them in water or exposing them to ethylene prior to sowing[].
Seed, harvested at 12% moisture content and stored, will retain its viability for several years[].

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