Cultivation of Saffron

Botany

Crocus sativus L. is a perennial plant having a depressed globule-shaped underground corm, 3–5 cm in diameter. The leaves are narrow, grass-like, 30–50 cm long. The flowers, one to four per corm, open before leaf emergence, and consist of six violet petals expanding outwards at the top. The pistil is made up of a bulbous ovary from which a slender style arises which is pale yellow and divides into a brilliant orangered, three-lobed stigma, 3–5 cm long. There are three stamens per flower, with twolobed anthers.

Climate

Saffron begins its growth in autumn, retains its leaves in winter, and enters a dormant state by the end of spring, so as to escape the high summer temperatures. A mild subtropical climate is considered most suitable for saffron cultivation.

The regions in which saffron is grown in Greece are characterized by a specific microclimate: annual precipitation exceeding 500 mm, 6–7°C average minimum temperature and 13.5–19°C average maximum temperature during October and November. The crop endures drought, but at certain stages of its growth water is indispensable. These critical times, when rain or irrigation is necessary, include March and April, when the corms grow, and September, for quantitative and qualitative improvement of the crop.

Soil

Saffron grows in a wide range of soils, but thrives best in deep, well-drained clay-calcareous soils that have a fairly loose texture and permit easy root penetration. The soils need not be rich in nutrients. However, low — and high-pH calcareous soils, as well as poorly drained ones, are unsuitable. An analysis of four typical soils in which saffron is cultivated in Greece is shown in Table “Analysis of four typical soils supporting saffron cultivation in Greece”.

Propagation — Lifting up of the corms

Saffron is propagated by corms. Each mother corm produces three or four new corms in the subsequent (second) year, while the mother plant itself decays. In the third year, 1–6 new corms are produced from each mother corm of the previous year, which also then decays. In the fourth year corm production declines, so only one or no corms are produced from a mother corm, which itself decays. This continues until the fifth and sixth years. Thus, in the position occupied by the initial corm in a new plantation (first year), one finds 3–4 corms in the second year, 20–22 corms in the third year and 18–20 corms from the fourth year onwards. The new corms begin to form after the November blossom and complete their development before the foliage dries out in May.

The plantation may be kept economically profitable until the seventh year by exploiting the flowers for a number of years. The lifting up and harvesting of corms to be used as propagation material takes place after leaf drop, from June to September, preferably from old (5 to 7 year) plantations, which can produce nearly 6–7 tons of well-formed healthy corms per ha. The corms are stored in a cool, dry place. Within a maximum of 2 months they can be transplanted in the field to establish a new plantation. For a hectare of new plantation, 2–3 tons are needed. A well-developed corm should be 22–25 mm diameter and 35–40 mm high on average. Before transplanting, the corms must be dipped into a fungicide solution (usually PCWB 75 W.P.) for 5 min. The suggested application rate for PCWB 75 W. P. is 150 g active ingredient per 100 kg of water.

Field Preparation Before Transplanting

A new plantation can be established between May and September. Before transplanting, the land should be well prepared to a depth of 30–35 cm by ploughing two or three times, depending on the prevailing climatic and soil conditions. The first ploughing is performed in July and the second in August. Before the second ploughing, 20–30 tons per ha of well-fermented animal manure are spread over the land surface, to be incorporated into the soil by the subsequent ploughing. The third ploughing is performed 8–10 days before transplanting for fine soil preparation and incorporation of mineral fertilizer. After the last ploughing, drainage troughs are formed every 10–12 m to ensure good drainage of the field in case of heavy rainfall.

Saffron: Corm Planting

The corms used to be planted in furrows formed with a plough. The workers placed the corms upright in the rows, 11–13 cm apart along the row at a depth of 15–17 cm. The corms were covered with the soil turned over by the plough as the next furrow was formed. The distance between the rows is 20–25 cm. Therefore 230,000– 250,000 corms per ha are needed to obtain a good plantation. Corm planting is followed by a light harrowing. Nowdays, the transplantation is carried out by machine, which was sophisticated by the growers themselfs. The best period to establish a new plantation is June. After that, no more cultivation is needed until September, when superficial chiselling can be performed to a depth of 6–8 cm.

Cultivation in the Old Plantation

When the plants in the old plantation (second to sixth years) begin to dry out in May, all the weeds are cut and removed from the field. The soil is then cultivated to a depth of 10 cm. The first cultivation consists of chiselling in early June, and this is then repeated in July and September.

Fertilization

At the last chiselling in September, 40 units of N, 30 units of P2O5 and 40 units of K2O per ha are applied and incorporated. Some growers apply another portion of 30 units of N the following March as a surface dressing in NO3– form. In some instances chlorotic symptoms are observed, and these are attributed to Fe or Mn deficiencies. To confront or alleviate Fe deficiency, chlorotic plants are watered with an organic Fe solution (Sequestrene 138, Fe), at a rate of 30 g of organic Fe per 10 m2 of soil, dissolved in a small quantity of water. When Mn is deficient, soil applications of 200 kg per ha MnSO4 are used, or the plants are sprayed with an aqueous solution of 1%o MnSO4.

Weed Control of Saffron

Many weeds compete with the crop. Most common are Anagalis arvensis L., Amaranthus blitum L., Avena fatua L., Capsella bursa pastoris L., Cichorium intybus Jacq., Fumaria officinalis L., Papaver rhoeas L., Sinapis arvensis L., and Sonchus oleraceous L.

The best weed-control method consists of hand-weeding, hoeing. These are the most effective and environmentally friendly ways, but also the most expensive. Another way is the light chisseling. The work begins after flower-picking in November and lasts till April. Over the past few decades, scientists have explored and experimented with the use of more and more herbicides for weed control. According to our trials, the best control is achieved with the herbicides Simazine (Gesatop 50%) and atrazine (Gesaprim 50%) at a rate of 10 kg per ha.

Diseases and Pests

The most serious fungal disease of saffron is Rhizoctonia crocorum (PERS) D.C. which causes corm decay. There are several ways to control this fungus: (a) removal and burning of the infected plants, (b) in fields heavily infested with this fungus, a 5-year crop rotation is advised, and (c) watering the root system of diseased plants when the first symptoms became apparent with a curative solution of the fungicide P.C.N.B. W.P. (Brassicol) at a rate of 1.5–3 g active ingredient per m2.

Other pests that cause serious damage to saffron plantations are rats, which eat the corms, and moles, which destroy them. Rats can be effectively controlled using poisonous baits and moles by using a smoking gas apparatus or poisonous-gasreleasing tablets placed at the entrance to their tunnel. Special handmade guns have also proven satisfactory against these pests.

Saffron: Flower Picking

Saffron flowers are ephemeral. If they are exposed for too long to sunny, windy or rainy weather, their stigmas and styles lose their colour and quality and their perfume deteriorates. Flowers must therefore be picked daily during peak flowering and every other day at the beginning and end of the flowering period. The flowering period starts around the beginning of October and lasts for about 30–40 days, depending on the prevailing weather conditions. Peak full-flowering coincides with the second decade of October. The flowering period of each plant may last for up to 15 days.

Flowers are picked by hand, from sunrise to sunset (). The flower is cut at the base of the petals with a slight twisting movement or with the fingernail. The cut flowers are collected in baskets. The largest saffron yields are obtained from third–and fourth-year plants. A product with excellent quality characteristics is reaped under temperatures ranging from 13°C to 19°C and a relative humidity of 60–65%. Rains 10–15 days before flower-picking provides excellent flowering and high production, whereas under drought conditions small flowers with small stigmas are expected.

Separation of Stigmas/Styles from Stamens

The separation of stigmas/styles and stamens from the petals is carried out at home within 1 day of collection. First, the flowers are placed in small quantities on a blanket made of goat’s wool. Second, with an airstream created by swiftly moving, specially manufactured, leather-bottomed frames in the old days — on which a thin layer of saffron flowers was spread-or by electric ventilators nowadays, petals are separated from stamens and stigmas, which stick to the goat’s wool blanket from where they are subsequently collected (). Next, the red (stigmas and styles) and yellow (stamens) saffron are separated, via one of two methods: (1) by hand, the best but also the most expensive method, used many years ago (2) using a wire screen with 6×6 mm holes, which can be either flat or cylindrical. A flat screen yields up to 80% separation, whereas a cylindrical screen yields 90% separation.

Drying

When stamens and stigmas/styles are dried together, the stamens’ pollen pollutes and deteriorates the red saffron. It is therefore recommended that they be separated first, before drying. The drying process consists of the following steps: The fresh saffron is placed on 40×50 cm trays with a silk-fabric bottom. A thin layer of saffron (4–5 mm) is spread along this fabric and then these trays are piled on frames with shelves 25–30 cm apart (). The frames are then placed in a dark room or in a storage room for drying, heated with a firewood stove, and the room temperature controlled. During the first few hours of the drying process, temperature is maintained at 20°C, it is then raised to 30–35°C. The drying process is terminated when the moisture content of the product has been reduced to 10– 11%, usually after 12 h. If the red (stigmas and styles) and yellow (stamens) saffron are still together after drying, they can be separated at this stage. At the same time, all foreign substances (soil, hairs, threads, etc.) are removed from the dried saffron product (). The pure dried saffron is kept in hermetically sealed glass vases or tin cans at 5–10°C.

Production

To produce 1 kg of fresh red saffron (stigmas and styles), one needs around 80 kg of fresh flowers. However, to produce 1 kg of dried red saffron one needs 120,000– 150,000 flowers, or 5 kg of fresh stigmas and styles. The yield of dry red saffron largely depends on weather and soil conditions and the culture treatments the crop has received. In a high-quality plantation, the following annual yields, expressed in dried red product, are expected:

In the first year after planting        3 kg per ha

In the second year after planting    10 kg per ha

In the third and fourth years after planting   15 kg per ha per year

In the fifth and sixth years after planting     10 kg per ha per year

On average, a hectare, within 6 years, produces (a) 60 kg of red saffron (stigmas and styles), (b) 20 kg of yellow saffron (stamens).

 

Selections from the book: “Saffron. Crocus sativus L.”. Edited by Moshe Negbi. Series: “Medicinal and Aromatic Plants — Industrial Profiles”. 1999