Saffron, the world’s most expensive spice, has been used as a seasoning, fragrance, dye and medicine throughout history. Saffron refers to the three bright-red stigma in the male saffron flower. It is dried and used in cooking to colour, flavour and add a unique aroma to the meal.
Each saffron flower produces three red stigma. They are 25–30mm long and weigh, on average, 0.007 g combined once dried, so approximately 150 flowers are required to yield just 1 g of dried saffron. Harvesting the stigma is typically done by hand, peeling the leaves of the flower away and removing the stigma with a nail or knife. The manual labour involved in growing and harvesting saffron is one reason why it is so expensive by weight.
The use of saffron as a spice is thought to have originated in the eastern Mediterranean nearly 4000 years ago. Since that time, it has maintained its position as the world’s most expensive spice, worth more than its weight in gold.
Saffron is native to Mediterranean climates so prefers cold winters and warm dry weather in the summer. Therefore, in theory, saffron may seem like a marginal crop to grow in the Rotorua catchment, where some summers have a lot of rainfall. However, studies have shown that if the soil conditions are correct, it can be grown in other climates, hence its inclusion in the Rotorua Land Use Directory. It could be successfully grown in the parts of the catchment with the least rainfall.
Another plus for growing saffron in Rotorua is that the crop prefers cold winters and can withstand substantial frosts, which is an encouraging sign. Trials are required to ensure a crop in Rotorua can produce sufficiently high-quality saffron.
Saffron threads: The highest-quality saffron (which fetches the highest price) must be picked from the flower within 48 hours, and dried quickly. It is important to dry the saffron correctly because over-drying results in a loss of colour and aroma, but insufficient drying can result in rot. Saffron is a known source of potassium, zinc and copper. Scientists are researching its potential as an antidepressant and as a treatment for Alzheimer’s disease.
Saffron corms: There is potential to sell saffron corms to other growers. Wild About Saffron, located in North Canterbury, sells corms to commercial and private growers.
All saffron is produced from the flower of the Crocus sativus. There are various cultivars that give the saffron thread different characteristics in terms of colour and aroma, and these typically arise regionally due to climate, soil and other external factors.
The flowers coming from the crocus are actually sterile, meaning the only way to reproduce the corms is to use vegetative means, or by corm multiplication. They readily bulk up and small new corms are easy to divide from the parent.
There is potential to service the local market through boutique food stores, local restaurants and farmers markets, but there is also potential to export.
There is export potential to Australia. Wild About Saffron sell their product to a buyer in Australia who has pre-ordered their entire crop. A quarter hectare of about 12,000 corms yielded one kilogram of saffron thread which sold for between $15,000 and $20,000.
Export will put the producer in competition with countries like Iran that can produce a competitive price due to low labour rates. However, a high-quality product will fetch a higher price.
Saffron comes from the flowers of the autumn crocus. This small corm flowers in the autumn, has foliage in the winter that dies off in the spring, and the corm goes through summer dormant. Corm sales begin in November and run over summer for planting in December to March. One thousand medium corms cost $2012.50 through Wild About Saffron.
Traditionally, saffron is grown on raised beds to allow good drainage and easy access for picking. Flower yield is highly dependent on corm density and corm size, and there is a lot of literature explaining the different corm quantities, spacing and depth methods used in various countries.
According to the Otago Crop Database, saffron beds can be planted 1 m apart with 50 corms per square metre. A density higher than that will result in the need to dig up, divide and replant the corms earlier than the typical four years, so a lower density will save a lot of work.
Corms are planted out during their dormant period in summer. Recommended planting depths for corms vary from 7.5–10 cm to 15–22 cm. Planting depth affects corm production as more buds sprout from shallow-planted corms than from deep-planted ones, resulting in more daughter corms.
Corm size has a significant effect on the production of daughter corms, the production of flowers and the yield of saffron. The larger the mother corm, the more daughter corms will be produced in the annual cycle, which increases the potential for higher yields in subsequent years.
Crop and Food research shows each original mother corm above 30 g produced an average of six new corms (in the second year), while the mother itself decayed. In the third year, the total mean corm number had risen to 22 new corms from each original mother corm, while in the fourth year that total had risen to 65.
The weight of corms produced is also affected by the weight of the original mother corm. When the original mother corm is above 30 g, the total weight of replacement corms doubles in the second season, is 10 times heavier than the original in year three, and in year four is about 16 times heavier.
New saffron corms also grow above the old ones each season, so they creep towards the soil surface by 1–2 cm each year. Therefore, the crop needs to be lifted and replanted periodically. This occurs about every four years in Spain, but fields may last up to twelve years or more under non-irrigated conditions in Kashmir. Replanting is normally done when yields begin to fall due to overcrowding or damage to corms that are too close to the soil surface.
At a Clyde crop studied by Crop and Food, large corms were planted at least 10 cm deep, while smaller corms were planted at 7–8 cm. Saffron was grown in beds with four or five rows, each 20 cm apart. Corms were planted 10 cm apart in the row. This gives a final density of 50 corms/m2.
In traditional saffron culture, large amounts of farmyard manure are applied to the saffron fields before planting, and typically 20–30 tonnes per hectare are incorporated during cultivation. This material supplies nutrients, but its other major role is to improve soil moisture-holding capacity and structure under non-irrigated conditions.
Under traditional growing systems, no further fertiliser was applied after corm planting. However, recent data suggest that at least some annual fertiliser applications are beneficial and a base dressing of 80 kg P/ha and 30 kg K/ha followed by a split application of 20 kg N/ha in autumn and again immediately after flowering is recommended.
Some growers use a mulch of sawdust to cut down on the requirements for hand-weeding or the use of herbicides. Mulch is also a useful way of maintaining soil moisture.
Weed control is the main activity outside the harvest period. After about four seasons it is common for the beds to start to become crowded, and production drops. This is the time to lift the corms and divide to plant more area.
Harvesting saffron is an incredibly time-consuming and labour-intensive activity. Flowers are usually picked daily in the morning to catch the flower before it is open. This helps with the harvesting process. The flower is cut at the base of the flower stem with a slight twisting movement, or by cutting with the fingernail.
The flowers are then taken for processing, where they are opened by hand and the stigmas removed for drying. If this is not done immediately after harvest in the field, the flowers should be chilled.
A small domestic dehydrator set to 30°C for 24 hours will usually suffice for drying batches of stigmas. Once dried, the saffron must be carefully handled so it does not break. It is usually packaged in an airtight storage container for sale.
The drying process is extremely important to ensure a high-quality product. It should also be stored in the dark to avoid bleaching. The brightness of the saffron is an easy identifier of high-quality produce.
Requirements will vary depending on the type of production. Installing raised beds, for example, will add significantly to start-up costs.
Rain or cold during the flowering season spoils the saffron, so shelter may be required. Fences may be required for pest management. Irrigation may be required if there is not enough rain during the autumn-winter-spring seasons.
After preparing the ground and planting, most work on a saffron block is done by hand. This means requirements for a spray pack and kneepads. At harvest, a dehydrator is needed to dry the crop.
Saffron thrives in environments with cool to cold winters with autumn-winter-spring rainfall, and warm dry summers with very little rainfall. It can stand substantial frosts. Rain or cold weather during flowering spoils the saffron and persistent wetness and high temperatures encourage disease. If there is not enough rain in the autumn-winter-spring, irrigation may be necessary, so access to water and irrigation should be considered in the feasibility phase.
No research is available for nitrogen leaching of saffron but it is not considered to be high. Any land use change to saffron planned for the Lake Rotorua catchment would need to be modelled for nitrogen leaching.
Light, friable soils with high nutrient content are best, for example well-drained sandy or loamy soils. Saffron grows best in deep, well drained clay-calcareous soils with a loose texture that permits easy root penetration.
Pest and disease control
Rabbits, rats and birds can cause problems in saffron fields by eating or lifting corms.
Corm rot is a potential disease if conditions are moist/warm/humid in the spring and summer months, though this can be treated with anti-fungal agents.
To guard against possible fungal or bacterial diseases before planting, the corms can be dipped for five minutes in a solution of 20 g Benlate® and 10 g Captan® mixed in 10 litres of water.
Even though saffron is a low-growing plant, shelter from the wind is advisable. It will reduce the amount of damage to the plants and subsequent disease problems. Be careful with design to allow the plants to get the maximum amount of sunshine during the growing season.
 Crop & Food Research, (2003). Growing saffron – the world’s most expensive spice. Crop & Food Research [Broadsheet] Number 20, August 2003. Retrieved 7th March 2017.
Yields vary depending on location and grower experience. Research done at Redbank near Clyde in the 1990s showed yields varying between 3–5 g of dried saffron per square metre of bed.
Although some small sales have been completed returning $20/g to the grower, bulk sales to commercial entities in the overseas markets are likely to be $6–8/g. Saffron grown in Kashmir is available for as little as $2/g. Quality lines will always attract higher prices.
Wild About Saffron
Wild About Saffron is a North Canterbury lifestyle block producer selling saffron corms commercially.
Growing Saffron – the world’s most expensive spice Crop & Food Research August 2003 (http://www.boobookhill.com/Kiwi%20Saffron.pdf)
Morrell, N. (2013, November 27). ‘Growing saffron: troubleshooting problems’, The Rural (http://www.therural.co.nz/horticulture/growingsaffrontroubleshootingproblems)