Some people suggest saffron is a spice made of red gold. We ask three important questions: what makes it so special, why is it so expensive and should we try to adapt it for growing in CEA?
Zafferano Siciliano Crocus produces large saffron stigmas.
Saffron (Crocus sativus L., a member of the Iridaceae family) is prized for its unique yellow color in culinary dishes and loved by chefs for its flavor in many of our foods. The high cost comes from the fact that it needs to be grown in a particular climate and the long red stigma must be laboriously collected by hand.
In the US, saffron is traded for up to $10,000 per kilo but this is highly dependent on the final graded product (graded 1- 4, 4 is the best quality and has a high safranal content with the red stigma separated from the yellow anther). The problem is, it takes around 150,000 flowers to produce 1kg of dried saffron. So we want to know, is it really worth it for CEA farmers? Let’s take a closer look at saffron’s history and the pros and cons of growing the most expensive spice in the world.
A long illustrious history of production
Ancient artworks revealed saffron was domesticated around 300 to 1600 BC and was thought to have been originally harvested as a mutant of Crocus cartrightianus which was abundant around the time in the Mediterranean.
The origins of saffron agronomy date back to Iran and today the country is responsible for producing over 90% of the world’s saffron where it has both historical and ceremonial importance in Persian culture. Other areas of production stretch across the Mediterranean where conditions are perfect for growing most notably North Africa, Morocco, Spain, Greece, Italy and India. The Spanish love the color in traditional paella whereas the Italians use it for signature risotto dishes like Risotto alla Milanese.
How does it grow naturally?
Visible two to three flowers per saffron corm
Saffron is adapted to arid regions and has an annual life cycle, but it is generally cultivated as a perennial crop by controlling corm bulb growth for the following year. It is a sterile triploid geophyte and is relatively slow to replicate through daughter corms each year. In the field, corms that die back after flowering and unusually have no cold requirement to break their dormancy. They can be lifted from the field during this time and stored in a dry shed before planting out again in spring, although they are hardy and can withstand low soil temperatures.
Saffron has immense health benefits
Saffron is abundant in phytochemicals, particularly picrocrocin which breaks down during the drying process to form safranal, which gives it the distinctive earthy taste. Another carotenoid pigment crocin, produces the golden yellow color when mixed with rice. Saffron also contains non-volatile antioxidants including lycopene and zeaxanthin which we identify with a Mediterranean diet, that are great for a long healthy life.
Crocus sativus L. has a wide array of medicinal and nutritional uses. Traditionally it goes way back as a drug alternative for many conditions such as heart disease, obesity, Alzheimer’s and diabetes. Several studies confirm the medicinal effects of the plant. Antioxidant effects demonstrate free radical scavenger activity that modulate inflammatory mediators, humoral immunity and cell-mediated immunity responses.
There are several clinical studies of these effects in its derivatives, safranal, crocin and crocetin. Researchers in Iran recently identified saffron as an effective treatment for mild postnatal depression. Saffron has since been shown to have mood altering effects thought to be the result of balancing neurotransmitters serotonin, dopamine and norepinephrine in the brain. In placebo comparison trials saffron had significant effects on levels of depression and displayed similar antidepressant efficacy to pharmaceuticals.
A double blind study of more than 80 people found the effects of the spice effective in treating depression in adolescents, without any side effects or fear of withdrawal symptoms when stopping the saffron. Saffron extract (affron®) was given for 8 weeks and it was found to improve anxiety and depressive symptoms in youths with mild and moderate symptoms. Adults reported more mixed results so more studies are needed to be conclusive in the understanding and role of saffron in the treatment of depression.
Why do we need high value crops like saffron in CEA?
Growing saffron in a controlled environment can have many advantages; it’s cleaner, free from pests and disease, nutrients are delivered directly to the root mass, aeration with dissolved oxygen increases biomass, temperature can be maintained without fluctuations and light intensity can be well managed. Saffron needs high intensity light and this can be delivered by high efficiency LEDs without fluctuation, eliminating weather dependent uncertainty in the field.
Despite the relative ease and low maintenance of growing in a controlled environment, it is the high flower numbers required to produce the end product and subsequent labor intensive ‘picking’ time that are the limiting factor. While in the field it is possible to grow three or more flowers per bulb per season (due to the daughter corms still being attached) the spacing requirements are more difficult to estimate in CEA until trials show optimized growth in a square meter space as smaller daughter corms will produce smaller stigma. We have no knowledge of large scale CEA production data and comparison to field harvests but scaling up in CEA may be more prohibitive due to labor costs. Perhaps automating this process in the future with robotic tweezers or re-engineering tissue culture pickers to use image analysis software with an ability to pick out the red stigma and separate from the anther would be useful, but we are some way off that at present.
Saffron has a high Market Value
Regardless of the issues, saffron continues to be of interest to CEA growers due to its high value and growing global demand as a medicinal plant and diverse applications in the food industry as well as for cosmetics and dyes.
The global saffron market size is expected to reach USD 721.5 million by 2028, according to a new report by Grand View Research, expanding at a CAGR of 8.5% over the forecast period.
Buyer beware! If you buy saffron and it seems cheap it’s more than likely to be fake!
Fake saffron is rife within this market and includes corn silk threads, safflower (an unrelated thistle), coconut filaments or even dyed horse hair, or shredded paper.
Safflower (in tissue culture above) Carthamus tinctorius, is the most likely culprit. It is a highly branched, herbaceous, thistle-like annual plant in the sunflower family Asteraceae and is often substituted for saffron. Each flower head contains 20–180 individual florets that can be confused with saffron to the untrained eye but the color gives it away as they are less intense than saffron stigma.
Dyes used to color fake saffron will dissipate quickly and this can be tested easily in water. Despite this, safflower has some excellent qualities as an oil in its own right and is commercially traded in the EU.
Temperature, light intensity/spectrum and humidity are particularly important in saffron cultivation. According to researchers in Vermont there are five main phases to the lifecycle of saffron production, sprouting, flowering, vegetative phase, production of replacement corms, and the dormant phase. Leaf area index, crop growth rate, relative growth rate, net assimilation rate, and leaf area ratio are all important.
A few entrepreneurs are paving the way by growing saffron in CEA. Dr Ardalan Ghilavizadeh pictured above is an expert hydroponics saffron grower from Iran and currently working in Berlin.
Saffron is a short-day plant so requires a period of around 12 hours in the dark and 10-12 hours per day lights on (16-18hrs during flowering). According to Urbanleaf, saffron can be grown indoors and they suggest it will require a DLI of 15+ mols/m²/d to flower. They go on to propose that 24W light bulbs can be placed around 6 inches away from the top of the plants to deliver a PPFD of 500 μmol/m²/s. Ideal temperatures for saffron flowering are around 70°F but anything between 50 and 100°F grows well. We have some preliminary trials with saffron but experimenting with light spectrum may achieve the best results to promote flowering and maintain a stable temperature during flowering. Growing in hydroponics follows similar conditions to other flowering plants and saffron displays a wide pH range of 5.5 – 7 but it’s best stay around 6 for maximum nutrient uptake at EC 1.4.
As with any production, IPM is important since saffron is prone to many diseases. Pathogens include fungal corm rot, nematodes, bacteria, and viruses. Diseases mostly appear as a consequence of physical damage or attacks by insects particularly mites and aphids.
Propagation of Saffron Corms
Saffron male seed is sterile so it is propagated vegetatively using corms. Flower yield is highly dependent on corm size and density but lack of availability and diversity of plant material presents a major constraint for large scale CEA saffron production. A large corm above 8 grams produces three to four small daughter corms, which take 2 to 3 seasons (in the field a season is one calendar year but in CEA there is potential for four harvests annually) to achieve the size and weight for flowering.
Forcing the bulbs through regular dormancy periods via CEA may help to promote cormogenesis.
Crocus sativus corms like rock wool for support to protect them against getting too wet. The method of hydroponics i.e. NFT or aeroponics must not allow the bulb to get too wet so it should sit proud of the rock wool substrate. They will root very quickly, around a week in our experience with aeroponic growing.
Saffron is relatively slow to propagate and only produces a few vegetative corms on the main plant annually in late summer after flowering has finished and the leaves die back. Breeding programs are needed to increase diversity of the corms and micropropagation may provide a solution to access of clean stock material. Saffron research is limited with only a handful of teams working on genetics in India, Iran and Europe. This crop needs preservation of genetic biodiversity to protect its quality and sustainability for future agricultural production.
Genetic diversity in corm supply is an issue so indirect organogenesis may provide new routes to improve cultivation of saffron. Tissue culture micropropagation, somatic embryogenesis, organogenesis, gene editing and in vitro cormogenesis can all help regenerate pathogen free reproduction of this plant. We are working to perfect this process.
Harvest first thing in the morning according to Dr Sally Francis, a field grower from Norfolk in the UK. The stigmas must be dried soon after harvest as they can become moldy. Besides the important role that dehydration plays in the preservation of saffron, it is also a necessary process to generate organoleptic properties in fresh stigmas. Dehydration treatment brings about physical and chemical changes necessary to achieve the desired quality of saffron. But be careful drying as over 150F can cause degradation of the phytonutrients.
Economics of growing Saffron in CEA – is it worth it financially?
The high retail value of saffron is maintained on world markets predominantly because of labor intensive harvesting methods but if this was not an issue could growing saffron in a CEA farm give a good profitable return?
The circle of saffron: daughters accumulate after the mother’s die back during dormancy, sometimes there is a large variation in size depending on fertigation. We can achieve this easily in hydroponics applying fertilizer at the correct intervals to increase corm density.
Let’s examine a theoretical scenario growing saffron in CEA reaching the highest market value of $10,000/Kg and play a game of dpi or in this case cpi, corms per inch.
On a 1 meter square shelf with a light intensity PPFD of 500 μmols/m2/s we can potentially grow 150 saffron bulbs (and assuming they each produce one dominant flower) with a spacing at least an inch apart to allow for flower development. Assuming they are forced to produce flowers 4 times per year, this rate could produce 600 flowers in a 1m2 area annually. If 150 flowers produce 1g dry weight, a yield of 4g of dry weight saffron is possible from 150 corms per square meter annually (four harvests).
Assuming a 10 layer shelf with lights spaced 20” apart, there is potential to scale up to 40g in a vertical space and 10 bays could reach 0.4kg (in reality it should be higher depending on how many flowers the corm produces). Depending on the grade this could net a return of $4,000. Not a bad return if you exclude capital startup costs. However high energy consumption and revenue costs may substantially reduce profits per meter square. Calculations are difficult as it will depend on an hourly rate for a picker and the uncertainty of rising energy costs could also hamper the return on running such a facility.
Issues that affect future stability of growing saffron
The adverse effects of global warming and climate change on saffron flower induction could alter the way saffron is grown. As the global north becomes warmer and extreme weather events become more frequent we will begin to find these crops in more protected geo locations. Wars and poverty also play a role in agriculture and instability in the region could lead to reduced world availability.
Niche high value product for the food service market – is that why we should grow it?
While saffron may not be an obvious choice for most larger commercial CEA growers, it should not be discounted as a high value crop for the service industry, fitting with more niche restaurant based container farms. Saffron is fairly low maintenance until harvest and some are even automating growing, which will reduce labor costs as the stigma can be picked by the restaurants when required without post processing and delivered straight to the chef’s palette. The advantage is it can be grown anywhere, close to restaurants, in cities and of course we are biased but it may also go well with sushi and a side of real wasabi.
Janet Colston PhD is pharmacologist with an interest in growing ‘functional’ foods that have additional phytonutrients and display medicinal qualities that are beneficial to human health. She grows these using a range of techniques including plant tissue micropropagation and controlled environmental agriculture to ensure the highest quality control.
Unless otherwise stated all images are courtesy of The Functional Plant Company and property of Urban Ag News.