Prota 14: Vegetable oils/Oléagineux
Sp. pl. 2: 830 (1753).
2n = 24
Safflower, false saffron (En). Carthame, safran bâtard (Fr). Açafroa, saflor, açaflor (Po). Kartamu, alizeti ya miba (Sw).
Origin and geographic distribution
Carthamus tinctorius is known only from cultivation and probably originated in the Middle East. Other centres of diversity are Afghanistan, Ethiopia and India. Carthamus tinctorius has long been domesticated, initially for the orange dye obtained from the flowers for which it was already grown in Egypt in 2000 BC. Its use as an oil crop probably came later, but also dates back to pre-Christian times. The ‘Revenue Laws’ papyrus of Ptolemy II of 259–258 BC states that the king had a monopoly of production and marketing of safflower along with sesame and castor oils. Safflower was probably introduced into China around 200–300 AD, where it was initially cultivated for its dye and grown extensively, particularly along the Chang Jian and in Sichuan. From China safflower was introduced into Japan, where it became an important source of cooking oil. From the Middle East the crop also spread westward into Europe and the Americas. Sudan, Ethiopia, Kenya and Tanzania are the main producers in tropical Africa.
The edible oil extracted from the seed is now the main product of safflower. Although the oil is suitable for paint production, it is used mainly in cooking and for making salad dressings and margarine. Cultivars with a high oleic acid content make safflower oil a major olive oil extender, one of the reasons for the crop’s rapid expansion in Spain. In Australia cultivars yielding oil with a high linoleic acid content are preferred. The oil has industrial uses. In India it has been used traditionally to make ‘roghan wax’ used in the batik industry.
Safflower has long been grown for the dye extracted from the flowers. Depending on the dyeing procedure and the addition of other colorants and mordants, it imparts a yellow, red, brown or purple colour to cloth. With the introduction of cheap synthetic dyes, its importance as a dye source has greatly declined. However, dyes are still produced on a small scale for traditional and religious purposes. As a natural food colorant it is a substitute or adulterant for true saffron and flowers are commonly mixed with rice, bread, pickles and other food to give them an attractive orange colour.
The seed cake is used as animal feed. The cake from undecorticated seeds (botanically the fruit) containing matairesinol-glucoside is only suitable for ruminants. After removal of the bitter compounds, the cake from decorticated seed would be excellent feed for monogastric animals too, but decortication is generally too costly. Safflower meal and flour from decorticated seed are used in the production of high-protein human diet supplements. The flour can be added to wheat flour to make breads and pies. The hulls have been used to make potting mixtures for nurseries, packing and insulation materials, and as filler for bricks.
In Asian countries the young leaves are eaten as a vegetable, the seeds are used in cooking and the fruits as bird feed. Safflower herbage is valuable as green fodder and may be stored as hay or silage. The straw is also used as fodder.
Safflower has a prominent place as a cosmetic ingredient and to a minor extent in medicine. In China the flowers are used to treat illnesses such as cerebral thrombosis, male sterility, rheumatism and bronchitis, to induce labour and as a tonic tea to invigorate blood circulation and the heart. Safflower-based medicines also show beneficial effect on pain and swelling associated with trauma. In Mauritius the flowers are used to treat jaundice, while the seeds are considered laxative. The sap is believed to reduce salivation. The oil is applied to treat scabies. Some cultivars are grown as ornamentals, and safflower is also popular as a cut-flower, fresh or dried.
Production and international trade
World production of safflower has steadily declined since the mid-1970s, when world production of oil was about 630,000 t and exports about 210,000 t. In recent years production has increased again to about 800,000 t in 2005. The decline was mainly due to competition from hybrid sunflower and Brassica oilseed and the great expansion of soya bean production in South America. Major producers of safflower are India, the United States, Mexico, Kazakhstan, Ethiopia, Argentina, Australia and China. Most growers now market their crop domestically and only export the surplus.
Fruit of white-hulled commercial safflower is composed of 30–40% hull and 60–70% kernel (botanically the seed). The kernel may contain 35–60% oil. The proportion of hull was higher in the past and a handicap to commercial production, but the recently introduced thin-hulled types may hamper mechanical harvesting and processing. The kernel contains a drying oil. Two types of cultivars yielding different oils are recognized: oleic safflower oil and linoleic safflower oil. The fatty acid composition of the former is: palmitic acid 5–6%, stearic acid 1.5–2%, oleic acid 74–80%, linoleic acid 13–18% and traces of linolenic acid and longer chain fatty acids; the fatty acid composition of linoleic safflower oil is: palmitic acid 5–8%, stearic acid 2–3%, oleic acid 8–30%, linoleic acid 67–83(–89)% and also traces of linolenic acid and longer chain fatty acids. Safflower types producing oil with an intermediate fatty acid composition also occur. Safflower oil is stable and does not alter at low temperatures or when heated. It is pale or golden yellow and has a bland or nutty flavour depending on the processing method. The oil’s high linoleic acid content, low colour values, low free fatty acids, low content of unsaponifiable compounds and absence of linolenic acid and waxes make it suitable for the production of high quality paints, alkyd resins and coatings. After oil extraction, the residual cake of undecorticated safflower contains: protein 20–22(–25)%, hull 60%, residual fat 2–15% and crude fibre 30–40%. The presscake from decorticated fruit contains up to 42% protein. The high fibre content limits the value of undecorticated cake as livestock feed, but removing the hulls is costly. Undecorticated meal can only be used to supplement a grain, lucerne or silage ration to fatten cattle. It cannot be fed to pigs, except in small quantities, nor to poultry. However, hulled seedmeal can be given to pigs.
The flowers of safflower contain two major pigments: the water-soluble, yellow carthamidin and the formerly important dye carthamin, a flavanone which is orange-red and soluble in alkaline solutions. Flowers contain 0.3–0.6% carthamin. Flavonoids, glycosides, sterols and serotonin derivatives have been identified from the flowers and seeds, including matairesinol, one of the main lignan precursors in dietary fibre.
Erect, much-branched, glabrous, annual herb, up to 180 cm tall; root system well developed, brownish grey, taproot thick and fleshy, penetrating up to 3 m deep, horizontal lateral roots thin, occurring mainly in the upper 30 cm; stem cylindrical, solid with soft pith, woody near the base, grooved, greenish white. Leaves arranged spirally, sessile, simple; stipules absent; blade oblong to ovate-lanceolate, 4–20 cm × 1–5 cm, margins more or less spiny toothed, glossy dark green. Inflorescence a terminal, urn-shaped head, 2.5–4 cm in diameter; involucral bracts numerous, arranged spirally, outer ones oblong, constricted above the base, 3–7 cm × 0.5–1.6 cm, hairy outside, pale green, upper part leafy and spinescent, inner bracts lanceolate, 2–2.5 cm × 1–4 mm, apex bearing a spine; receptacle flat to conical, with abundant, whitish bristles 1–2 cm long and 20–80 bisexual flowers and a few sterile marginal ones. Flowers tubular, sessile, regular, 5-merous, c. 4 cm long, glabrous, mostly orange-red becoming dark red during flowering, sometimes yellow; corolla with 18–22 mm long tube and spreading, narrowly oblong to linear lobes 7 mm × 1 mm; stamens with filaments 1–2 mm long, anthers c. 5 mm long, fused; ovary inferior, ellipsoid, 3.5–4.5 mm long, 1-celled, style slender, c. 30 mm long, glabrous, stigma c. 5 mm long, bifid, yellow, with short hairs. Fruit an often obliquely obovoid achene 5.5–8 mm × 3–5 mm, 4-angled, glabrous, glossy white but often pale brown near the top, innermost fruits in a head often with pappus of bristles c. 6 mm long. Seed without endosperm. Seedling with epigeal germination; taproot strong; hypocotyl greenish white; cotyledons leaflike, obovate, c. 6 cm × 1.5 cm, greyish pale green; first leaves lanceolate with tapering base; juvenile plants with leaf rosette.
Other botanical information
Carthamus comprises about 15 species. Section Carthamus comprises Carthamus tinctorius and its 5 closest relatives, all annual species from western Asia with n = 12.
Because Carthamus tinctorius has been cultivated over a wide area since ancient times, and because cross-pollination is fairly common, variability in safflower is large. The morphological differences are most obvious in branching (height, density), leaves (presence or absence of rosette leaves, more or less spiny leaves), involucral bracts (form, pubescence, spiny or not), inflorescences (number and size of heads), flower colour (reddish, orange, yellow, white), and achenes (size, presence or absence of pappus).
Growth and development
Safflower generally lacks seed dormancy and can germinate in the head if rainfall occurs at harvest time. After germination, the seedling enters the rosette stage, characterized by slow growth, production of a rosette of leaves and development of a deeply penetrating taproot. When sown in spring, safflower generally has no rosette stage, while a long rosette stage occurs when it is autumn-sown. During the rosette stage plants are tolerant of frost, which allows them to overwinter. Cultivars in Ethiopia do not form rosettes, but form a stem immediately. Safflower is generally a long-day plant. Flowering is normally initiated by approximately 14 hours of daylight, but this can be modified by temperature, high temperatures accelerating flowering. Salinity may also accelerate the onset of flowering. Cultivars differ in sensitivity to daylength and daylength-neutral cultivars exist. In contrast to its relatively slow initial growth, safflower grows rapidly after the stem begins to elongate. When the plant is 20–40 cm tall, lateral branches start to develop. Stem elongation and branching are followed by the development of a flower head at the tip of each stem and branch. After the completion of growth of secondary branches and the formation of flower heads (75–100 days after sowing), flowers start to appear in the heads. Flowering begins in the head of the main axis, followed by the main branches; secondary and tertiary branches follow sequentially. Flowering normally begins at the head’s margin, proceeds towards the centre and takes 3–5 days to complete. Total flowering extends over 10–40 days. Safflower is basically self-pollinated, pollination ensuing as the style and stigma grow through the surrounding anther column at the base of the corolla. However, a high degree of crossing can occur, particularly in thin-hulled types. Bees or other insects are generally necessary for optimum fertilization and maximum yields. Male and female sterility occurs. Structural male sterility is linked with the thin-hull character and delayed anther dehiscence in this type is used to produce hybrid seed. A well-developed safflower head contains 15–30 or more achenes which mature in 4–5 weeks after flowering.
Safflower is basically a crop of semi-arid, subtropical regions, but its range has been greatly expanded by selection and breeding. It is distributed between latitudes 20°S and 40°N and its cultivation has recently even spread into Canada. In the tropics it is mostly grown at 1600–2200 m altitude, but large-scale commercial production is concentrated in semi-arid areas below 1000 m. Seed yield and oil content fall with increasing altitude. Seedlings can tolerate –7°C, some cultivars even down to –12°C. They become more susceptible to frost damage after the rosette stage. Average temperatures of 17–20°C appear to be best for vegetative growth, while the optimum temperature for flowering is 24–32°C. Adequate soil moisture reduces the adverse effect of higher temperatures.
Safflower requires about 600 mm of rainfall with a major portion falling before flowering. Under dry, windy conditions, which are most suitable for safflower production because it favours low disease incidence, 800–1000 mm are required. In places where there are no hot, dry winds, reasonable yields can still be produced as long as 300 mm of rain is available before flowering. Because of its extensive root system, safflower can be grown largely on residual soil moisture. If pre-planting soil moisture covers about two-thirds of the total water requirement, the remainder can be supplied by rainfall.
In the United States and Australia 1500–2500 mm of irrigation water is required to produce a high-yielding commercial crop. In Israel safflower needs a minimum of 600 mm rain plus a similar amount from irrigation. In Tanzania 400 mm rainfall plus 450 mm irrigated water are the minimum requirements, but crops supplied with 2250 mm of irrigation water in the dry season produce twice the wet season yield, partially due to less damage from diseases and pests. A rain-fed crop in India requires 650–1000 mm, but in the dry season under irrigation it needs 1800–2100 mm (less if the preceding crop is rice).
Safflower is grown by smallholders on a wide range of soils with pH 5–8. For large-scale production, fairly deep, well-drained, sandy loams of neutral reaction are preferred. Highest yields are obtained in dry regions on sandy loams with irrigation. Regardless of their fertility, shallow soils seldom produce high yields, and this is invariably due to insufficient moisture. Safflower is considered salt-tolerant, although many commercial cultivars are salt-sensitive. It is especially tolerant of sodium salts, but less so of calcium and magnesium salts. Salinity delays seedling emergence, while very high levels reduce germination. However, safflower is a suitable crop for saline soils, especially the recent highly salt-tolerant cultivars.
Propagation and planting
Chisel ploughs or subsoilers should be used to fracture compacted soil layers within the root zone because safflower is deep-rooted. Ideally, safflower should be sown 3–5 cm deep into moist soil, but when topsoil is dry and loose, seed may be planted 10–15 cm deep. The 1000-seed weight is 40–80(–100) g. Most seed drills are suitable for sowing safflower, but should be calibrated. It is sometimes recommended that furrow-openers be fitted to seeder units and the furrows to be only partially closed after sowing. Seed rates depend on cultivar and growing conditions. For large-scale rain-fed crops, seed rates are 10–15 kg/ha in very drought-prone regions to 30 kg/ha under higher rainfall conditions. Under irrigation and when cultivars with minimum branching are grown, 40–60 kg/ha is used.
Wide rows, 35–60(–90) cm with close in-row spacing, generally give the highest yield. Safflower can compensate for spatial variation by producing more secondary and tertiary heads per plant. However, while the seed yield may be little affected, less oil will be produced as seeds from these heads are generally smaller and have a low oil content.
Safflower is readily integrated into mechanized small grain production. During the rosette stage, safflower is a poor competitor with weeds. Mechanical weeding of young safflower is difficult, and pre-planting harrowing should aim at maximum weed reduction. While safflower is still small, finger weeders and rotary hoes can be used, but when plants reach about 15 cm in height, weeding should be limited to the inter-row. However, careful hand-weeding gives the highest yield. Pre-emergence herbicides combined with mechanical inter-row weeding are widely used in commercially grown safflower.
Nitrogen is the most important nutrient, phosphate requirement is moderate, and potassium is required only where there is a major local deficiency. At the levels normally applied, fertilizers generally have little direct effect on seed composition or oil percentage. However, by increasing seed yield, they increase total oil yield. Contact between seedlings and fertilizer should be avoided and N applications should be split when the rate is above 100 kg N/ha. Up to 150 kg N/ha is applied to current high-yielding cultivars grown under irrigation. Rainfed crops are given about 50 kg N/ha. Phosphate fertilizers are normally residues from animals and crops or rock phosphate. However, 5–12.5 kg P/ha has been recommended for smallholder crops in India, Iran, Pakistan and Afghanistan.
Intercropping safflower is possible and in Ethiopia safflower cultivation is closely associated with the distribution of teff (Eragrostis tef (Zuccagni) Trotter) and barley (Hordeum vulgare L.) with which it is mostly intercropped, Elsewhere, intercropping is not common because the yields are low as a result of competition. Safflower should not be planted on the same land for two consecutive years because it is susceptible to soil-borne fungal diseases.
Diseases and pests
Many diseases have been recorded on safflower, but few limit commercial production. Rust, caused by Puccinia carthami, is the most important disease attacking young safflower. Foliar diseases are prevalent in places where rainfall occurs between the late bud stage and near maturity; the most serious and widespread is leaf blight caused by Alternaria carthami. Root rots caused by Fusarium oxysporum and Phytophthora spp. including Phytophthora cryptogea and Phytophthora drechsleri are widespread and very damaging. Phytophthora drechsleri is especially serious in surface-irrigated safflower and its incidence and severity are increased if the crop has undergone moisture stress.
The majority of insects that attack safflower are of little economic importance and do not require control. However, the safflower fly Acanthiophilus helianthi can be very damaging and virtually preclude safflower growing. Pesticide use is often uneconomical and it is always necessary to balance control costs against allowable damage. Early planting and growing short-duration cultivars help reduce damage by evading infestation. Condica capensis (synonym: Perigea capensis) attacks at all stages of development and is common in India, Pakistan and South-East Asia. Bollworm (Helicoverpa spp.) and black cutworm (Agrotis ipsilon) occur in all countries that grow safflower and are of varying importance.
Harvesting of safflower usually begins 35–40 days after maximum flowering, when plants are quite dry but not brittle, involucral bracts on heads turn brown and fruits have a moisture content below 8%, preferably 5%. While harvesting is done manually in many areas, grain combine harvesters are quite suitable although they cannot cut as fast as in wheat or barley. Harvesting safflower is comparatively simple since the crop does not generally lodge or shatter. A mature crop is relatively immune to damage and may be left standing in the field for one month with little loss. Light cold rain or frost does little damage. However, certain cultivars germinate in the head if periods of warm wet weather occur at maturity. For smallholders, the extended harvesting period allows individual heads to be collected as they ripen. Generally, however, plants are uprooted, heaped and dried in the field for a few days and threshed to remove the seeds.
For the dye production, flower heads are collected every second to third day before they fade. Harvested flowers are washed and later dried.
The average seed yield of safflower grown under rainfed, intensive cultivation has increased steadily to 1500 kg/ha and nearly twice this under irrigation. Average yields in Ethiopia and India are about 500 kg/ha. Yields of straw are larger than those of small grain crops and may reach 5 t/ha.
Handling after harvest
Safflower fruit can be stored in bulk, where possible in grain bins, provided the seed moisture content is 5–8%. Safflower can be processed by most commercial oilseed plants either by pressure, solvent extraction or a combination of both. There are no special requirements. Carthamin is extracted from the flowers by first washing out the carthamidin in ample water and subsequently extracting the flowers with a sodium carbonate solution. Carthamin is precipitated from the solution using diluted acid.
Considerable research into safflower’s genetics and breeding has been done, including work on related species considered valuable sources of genetic material. Evaluation of germplasm collections showed large variability in agronomically important characters, including spininess, seed yield per plant, flower heads per plant, hull percentage, crop duration, rosette period, dry matter production and days to maturity. Resistance to the pest Acanthiophilus helianthi has not yet been found. The ARS-GRIN Western Regional Plant Introduction Station, Pullman WA, United States maintains a germplasm collection of 2300 accessions of Carthamus tinctorius and many related species. The Institute of Oil Crops Research, CAAS, Wuhan, Hubei, China holds 2300 accessions, the Regional Station Akola, NBPGR, Akola, Maharashtra, India 2000 accessions.
Reducing the hull percentage is a major objective in breeding safflower. Current cultivars with less fibre (17% of the fruit and 38% of the seed) and a higher protein content are preferred by stock feed manufacturers. Seed composition, oil content and quality (in terms of component fatty acids) are influenced by environment, including latitude, altitude, day and night temperatures and amount of rainfall during flowering and seed setting.
The discovery of a gene causing partial male sterility allowed more detailed study of heterosis and related processes. A mass emasculation technique has been developed, and in-vitro techniques enable large-scale production of selected strains. A variety of other methods under the general heading of genetic engineering are being reported. There is a major need to expand safflower’s adaptation through genetic research and breeding.
In industrialized countries where research has linked health and diet, demand for unsaturated oils has increased, thereby creating a growing market for such oils as health foods. This may lead to an increasing demand for and production of safflower. Potential yield levels, yield stability and improved pest control need research attention. The large genetic diversity gives ample scope to develop improved cultivars.
The use of dyes from natural sources in food products is gaining popularity because of possible harmful effects from synthetic colourings.
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Sources of illustration
• Oyen, L.P.A. & Umali, B.E., 2001. Carthamus tinctorius L. In: van der Vossen, H.A.M. & Umali, B.E. (Editors). Plant Resources of South-East Asia No 14. Vegetable oils and fats. Backhuys Publishers, Leiden, Netherlands. pp. 70–76.
Correct citation of this article:
Oyen, L.P.A. & Umali, B.E., 2007. Carthamus tinctorius L. In: van der Vossen, H.A.M. & Mkamilo, G.S. (Editors). PROTA 14: Vegetable oils/Oléagineux. [CD-Rom]. PROTA, Wageningen, Netherlands.
1, plant habit; 2, flowering branch; 3, detail of head; 4, lower part of flower; 5, upper part of flower (opened); 6, achene.
flowering plants in field
head in cross section with developing achenes