Saffron – a delicate, exotic and expensive spice from far away lands? Not necessarily so. Saffron spice consists of the dark red-gold, dried stigma of the saffron corm flower and has traditionally been grown outdoors on a commercial scale in countries such as Spain, India and Iran where the climate is warm and dry and labor cheap for the time consuming process of harvesting. However, saffron is not difficult to grow indoors and these days saffron bulbs are readily obtainable at the right time of year for those who want to grow some of their own exotic spice. While saffron bulbs may take up little space, their yield is somewhat low – it takes around two pounds of fresh flowers to give 2.5 ounces of red stigmas, which when dried results in a yield of 0.4 ounces of usable spice. Each saffron corm usually produces between one and three flowers in a season so yields per square foot are perhaps one of the lowest of any hydroponic plant. On the other hand, most recipes only require a few strands of dried saffron, so production from a square foot of growing space is usually sufficient for most gourmets.

What is saffron?

There are many imitations and cheap substitutes for saffron on the culinary market. Some of these consist of counterfeit strands while others are just color substitutes of cheaper spices such as turmeric. Saffron, although having a long shelf life, is best used within a year of drying and it is difficult to tell if product many years old is being sold as top quality spice. Nothing equals the intense color and subtle flavor of true saffron and some even claim that there are slight flavor variations between saffron grown in different regions of the world. Saffron is the world’s highest priced spice and is often sold by the gram or half gram of the best quality product. As with most crops, it is likely that the growing conditions, soil type, nutrition, temperatures, plant health and harvesting, handling and drying practices play a major role in the final quality and flavor of this spice. Hydroponic production where we have control over basic nutrition and supplements and indoors where temperature, light and the growing environment can be manipulated, give the potential for some extremely high quality saffron to be grown.

The saffron plant

The saffron crocus (Crocus sativus L) grows from a small rounded corm (similar to a bulb). The corms are purchased while dormant, and planted out in late summer or early fall when they rapidly burst into life with the production of small crocus flowers. This exotic spice is made from the dried red-gold stigma which forms inside the blue/purple flower. Each flower produces on average three stigmas which give three strands of saffron. After flowering, the plant resumes vegetative growth of thin, dark green strap like leaves and then multiplies itself with the production of many small daughter corms.

Nowadays saffron corms are sold by various seed suppliers and nurseries in small quantities for home gardeners to purchase. However bulbs are not usually available year round and are commonly advertised for sale in mid to late summer through until fall. When buying corms for the first time, it is important to realize that like many flowering bulbs, the corms come in size grades from very small (0.6 grams) which would be a non flowering type requiring an additional season’s growth, to very large (24 grams). The smaller corms are usually less expensive, but they may not produce flowers in the first season or produce a much lower yield of saffron and a lower number of daughter corms after flowering. The best planting grade for hydroponics is around 15 grams which is usually over an inch in diameter. The corms arrive dry in a dormant state ready for planting out.

Indoor Saffron

Indoors, there are two ways of running a saffron system – the dormant corms can be purchased, planted, flowered, harvested and the corms discarded, all over a six week period. Or after the short flowering period, the bulbs can be grown on, producing vegetation and new daughter cormlets over a period of many months, until they become dormant in mid summer. The first system means the corms are planted at a high density since they won’t be grown on and multiplied. This sort of bulb ‘forcing’ could also be carried out in solution culture systems such as those used for tulips and other flowering bulbs where the corm is supported with its base in water The second system needs more space for the plants to fully develop and many months of caring for the corms after they flower, although the reward is a supply of new corms which could be sold or given away to others and a higher yield of flowers in the next year. Tying up your hydroponic system with vegetative saffron for nine to 10 months however may not be attractive to those with limited space, although trays of saffron plants are cold hardly and can be put outside for winter and spring if necessary.

Corms can be stored in a dry place and planted out when the hydroponic system is ready. The spacing should be approximately four to five inches apart and 1.5 to two inches deep, in a tray of free draining, sterile growing media such as coconut fiber with some perlite mixed in. The media needs to support the plants, but at the same time be friable enough for the young corms to form without deformities so any substrate used for baby root crops would be suitable.

The flowers will have already been initiated in the corms during the summer dormancy period and flowering will occur when moisture is provided and temperatures start to drop in fall. Flowering is triggered by environmental conditions such as temperate and moisture which is easily manipulated in a hydroponic grow room. The ideal conditions during flowering are 16 hour day length with day temperatures of 62oF and night temperatures of 53oF. An indoor grow room or greenhouse situation means the flowers are protected from rain, moisture, wind and the lack of weeds makes harvesting of high quality flowers much easier.

The Grow Room

After flowering the foliage grows best at 60 to 65o F, with 12 to 14 hours of light to keep enough photosynthesis going to bulk up the developing cormlets. Saffron typically flowers in autumn over a short period, then produces a number of strap-like leaves which grow through winter, spring and into summer, providing food reserves for the corm and developing new cormlets. After flowering and harvest in autumn, foliage will develop quite rapidly and during this time, a standard vegetative nutrient should be given to the plants as required. Recommended EC levels are 1.2 – 1.4 during this stage. Leaf growth will continue until summer when the young corms start to rapidly develop around the mother corm.

In their natural environment, the saffron plants’ foliage dies back in mid to late summer, after the young corms have matured and as conditions become very warm and dry. The corms then go into a dormancy period which is essential for initiating the next season’s flowers which will bloom in the cooler, moist conditions of fall. In hydroponics we can easily replicate this by drying the media back after the cormlets have formed and the foliage has died down. Having a dig around one of the plants will soon reveal if the corms are ready for harvest and dormancy. The tray of saffron corms, once fully dried, can be harvested and stored away in a dry, dark place until they need to be planted out for flower production. This is a time consuming process as the saffron plant needs many months (nine to 10) after flowering, until harvest of the new corms with only one harvest of flowers per year obtained. However, each mother corm, after flowering will produce a number (four to 10 or more) young cormlets that can be used to produce more flowers and greater harvests of saffron spice in the following season.

Flowering and Harvesting

Flowering of the corms will typically occur quite quickly after planting; within a few weeks the first emerging flower buds should be seen. The flowers will fully open within three to five days and be ready for harvest. As each flower blooms, it should be plucked or snipped from the plant and taken away for processing. Inside the flower there will be two or three thinner dark red colored stigmas which form the saffron spice when dried; there will also be three, shorter, wider, golden colored anthers which usually have pollen on their surface – these are not part of the spice and should be discarded. The easiest way of removing the saffron stigmas from the centre of the flower, is to pull back and remove all the petals and then snip the red strands at the base. These will then need to be dried before storage. Saffron is very delicate and the strands should be placed on white paper and allowed to air dry and fully desiccate. Any slight breeze will blow the strands away and home dehydrators are not well suited to this. Being small and very light, the saffron will dry within a week in most cases and can then be stored in air tight glass jars. A small package of silicon desiccant can be used to make sure any additional moisture on the strands or in the air does not cause any storage problems. Insufficiently dried saffron can go moldy, so additional air drying time is recommended if humidity levels are high.

While it has become possible for home gardeners to grow a container or pot with a few saffron bulbs outdoors, often just for the novelty of seeing the flowers, there has not been a great deal of research into hydroponic or aeroponic production of this spice. It is likely that the best system will be similar to the hydroponic production of forced tulips and other bulbs with the actual flowering phase being carried out indoors or under protection to give the highest possible blooms, while the plants are propagated and bulbs grown outdoors through until dormancy. Outdoor producers are restricted to one crop of saffron per season, however with an indoor grow room, the environment can easily be manipulated to give the dry warmth of summer to initiate flowering followed by cooler, damper conditions to induce flowering whenever it is required.

References:

`The Growth of Saffron (Crocus sativus L.) in Aeroponics and Hydroponics’ Fredric V Souret and P J Weathers. Published in: Journal of Herbs, Spices and Medicinal Plants, Volume 7, Issue 3, 2000. ISBN 1049-6475

Supplies of saffron corms:

 http://www.nicholsgardennursery.com/

 http://www.whiteflowerfarm.com/

 http://www.richters.com/

The basic principles of plant propagation have been used for centuries, but these days, we have a whole host of new technology and knowledge to make the process faster and more reliable, and it’s only getting even more high-tech… 

Ever since the dawn of agriculture, plant propagation techniques have been under intensive study. Without reliable methods of plant multiplication we would have no crops to harvest and no way of creating future generations of improved genetic stock. While the basic principles of plant propagation have been understood and used for centuries, these days we have a whole host of new technology, equipment, products and knowledge that have made vast improvements in the reliability and speed of this process. Furthermore, researchers are still delving into many aspects of plant multiplication and uncovering new information to further improve the process of propagation of a wide range of species.

As indoor gardeners we have a major advantage when it comes to propagation. With precise control over the environment, heat, humidity, light, oxygenation, CO2 and other factors, propagation becomes a more reliable process. Couple this with advances in hydroponic equipment and products specifically designed for the nurturing of new plants, seed production and treatment technology, and knowledge of root formation compounds, hydroponic growers have all the tools required for successful propagation.

While high-tech equipment provides some valuable assistance with propagation, growers still need some basic knowledge about the best methods to use for different species. Ideally, even beginner growers should be able to multiply plants via seeds and cuttings and clones as well as know which method is best for each crop. In the early days of gardening this was relatively simple. Growers would sow seeds or take cuttings and clones from plants, poke them into the soil someplace warm and hope for the best.Often the results were not great and a certain failure rate was to be expected. Nowadays we have come to expect a high success rate with propagation due to advances in technology, the indoor gardening environment and a great deal more information.

Clones or seedlings?

The two main methods of propagation used by indoor gardeners are via seed and via cuttings and clones. There is actually a large number of techniques used on different species for propagation, such as bulbs, rhizomes, corms, air layering, root layering, division, offsets and plantlets produced on stolons and others. However, the majority of vegetable and herb species we grow hydroponically are produced via seeds and cuttings.

The advantage of cuttings is that the resulting new plant will be genetically identical to the mother plant the material was taken from. This means all the good characteristics of the plant are retained and we know exactly what to expect in terms of growth and yields from the propagated plantlets. The disadvantage is that pests, diseases and viruses carried on the mother plant can be transferred to the daughter plants. Cuttings also require a mother or stock plant to be maintained in a healthy state for cuttings to be taken from, so genetic material can’t be stored for extended periods of time in the way that seeds can. Cutting material, depending on species, can take anywhere from a few days to many months to form new roots, although most of the species we grown indoors are relatively quick to do so. Cuttings are often a preferred way of multiplying plants that are very slow or unreliable from seed. For example, a stem cutting of mint will form roots in water in a few days, whereas the tiny seeds take many weeks to produce a seedling large enough to plant out.

Seeds have the advantage of being small, portable and easy to store for a relatively long period of time. Most vegetable and herb seed germinates quickly, within a few days for most, and commercially produced seed usually has a very high percentage germination rate. Hybrid seed will have uniform genetics and has been bred for adventurous characteristics. However, open pollinated seed will not produce new plants identical to the parents. As you can see, genetics can be fairly random when hybrid seed is not used. 

Cuttings or clones?The technology

Some softwood species will easily root quickly, often in a jar of water; however, most species we want to clone benefit from some assistance, care and attention. After carefully selecting and preparing the cutting material from a healthy stock plant, a root promotion product should be applied. Back in the old days, there were just basic powders or solutions of an auxin hormone used by commercial propagators, these days we have a wide range of highly advanced and effective rooting compounds and bio stimulants formulated into easy to use gels, powders and solutions.  Based on extensive research into root promotion compounds, rooting gels now contain not just IBA or NAA, which are auxin plant growth regulators, but also other stimulants and bioactive compounds shown to be beneficial for this process. 

Auxin (IBA and NAA) are plant growth regulators which stimulate root development by inducing root initials that differentiate from cells of the young secondary phloem, cambium and pith tissue of the cutting material. IBA is most commonly used in these products as it is relatively stable and doesn’t break down due to enzymes within the plant. It’s well proven that use of a product containing an auxin such as IBA increases the percentage of rooted cuttings, the number of roots and the speed of root formation. However, advances in plant research over the last few decades and even quite recently have also discovered other root formation substances which are synergistic with IBA.

Since the 1950s it’s been known that boron (B) is essential for the development of adventitious roots on stem cuttings. Many researchers have found that whereas roots are initiated in response to auxin, boron was essential for the subsequent growth of roots. Thiamine (vitamin B1) is another root promotion substance in cuttings of many species. Studies have shown thiamine assists with promotion of rooting in terms of speed and number of roots formed. Many highly effective hydroponic rooting gels and other products contain boron, thiamine, humic or fulvic acids and a host of other vitamins, minerals and bioactive compounds that might be beneficial to root formation on cuttings.

More recently we have seen a range of microbial products being developed specifically to help promote root formation on cuttings and young seedlings. These microbial products are not new –the beneficial effect of mycorrhizal fungi on rooting of woody plant cuttings was reported in the 1970s; however, its only more recently that shelf-life stable and effective products have been available for smaller growers to purchase. These plant growth promoting rhizobacteria are thought to enhance root development either directly by producing phytohormones, or indirectly by inhibiting disease pathogens.

Along with increasingly effective rooting promotion gel products and bio stimulates, advances in propagation substrates and systems have seen sometimes miraculous improvements in percentage germination and cutting take rates. Root formation and germination are highly reliant on the correct environment as well as freedom from certain pathogens such as pythium and other root rot diseases. Sterile, highly aerated propagation media such as oasis, rockwool, foam substrates, coconut fibre, vermiculite and many new types of starter cubes are a vast improvement on trays of sand and peat historically used for propagation. Many of these new mediums have been created with specific air to water ratios to boost oxygen around the newly forming root initials or germinating seed. 

Other new propagation products are highly specific to hydroponics and include a wide range of different sized propagation systems–often termed `cloning machines’that mist highly aerated water and nutrients inside a chamber, maintaining the optimum environment for root formation. These types of systems are particularly useful for harder wood cuttings and difficult on root species as they speed up the rate of root formation.

Seeds: the technology

Just as with cuttings, seed germination has also seen some advances in technology and specialised materials. Most hydroponic gardeners these days raise seedlings in specially designed propagation mediums. These can be sterile foams, rockwool, oasis or any of wide range of synthetic materials or more organically based mixes of coconut fibre, composts and propagation cubes made from a bound matrix of these materials. As with cuttings, there are a range of bio stimulant products for seed germination and seedlings, including those based on humic and fulvic acids, vitamin and minerals and microbial inoculants. Along with a suitable germination medium, growers can utilize a range of propagation equipment from the easy to use heating pad to an enclosed germination chamber which maintains the right degree of heat, humidity and light once the seedlings emerge.

Seed technology itself has also improved in modern times. Many small and difficult to handle seeds such as lettuce can be purchased in pelleted form. For species such as lettuce, thermo pelleting assists the seed to germinate in a wider range of temperature conditions, while other seeds can be coated in growth promotants or fungicides to help control pre- and post-germination rot pathogens. Other seeds might be primed to promote rapid germination and most are viability tested before they are sold.

Tissue culture: small-scale technology

A newer technology as far as home gardeners goes has been the introduction of home tissue culture kits and equipment. Tissue culture is a way of rapidly bulking up huge numbers of plants from a small amount of material and has largely been in the realm of commercial propagators for decades due to the requirement for aseptic conditions under which to carry this process out. Recent technology has seen the use of scaled down tissue culture equipment being used by small growers and indoor gardeners, although a certain degree of skill is still required to carry this process out correctly.

There are a number of different tissue culture methods; however, the most commonly used is called adventitious shoot formation, where a small piece of plant is taken (like a root, leaf, bulb, scale or similar) then induced to produce many small shoots through application of plant growth hormone contained in the tissue culture gel medium. Normally, such plant parts would not produce new shoots, let alone masses of them, but the conditions inside the tissue culture flask and the application of the plant growth regulator causes this growth to occur. These shoots, once sufficiently developed, are divided up into individual clumps and grown on in another flask where they are induced to form tiny roots by application of another plant growth hormone in the agar gel substrate. Then the plantlets are grown until they are large enough to leave the protected environment of the flask, be potted up and grown on as normal plantlets. This procedure can be used for a wide range of plants; however, beginners often start learning tissue culture methods using an easy species such as African violet.

Current technologies used to increase the speed and reliability of plant propagation are a major boost for keen indoor gardeners. From simple seed germination to advanced tissue culture, we have access to specific equipment and products to make this a fun and productive process. No doubt in the future we will see further advancements in propagation technology and tools as research into these plant processes is continually ongoing.

References and sources of information

R G Linderman and C A Call, (1977). “Enhanced rooting of woody plant cuttings by Mycorrhizal fungi”. J. Amer. Soc. Hort. Sci 102(5): 629-632.

E Benizri, E Baudoin and A Guckert, (2001). “Root Colonization by inoculated plant growth promoting Rhizobacteria.”  Biocontrol Science and technolog Vol 11(5): 557-754.

W Middleton, B C Jarvis and A Booth, (1978). “The boron requirement for root development in stem cuttings of Phaseolus Aureus Roxb.”   New Phytologist Vol 81(2): 287-297.