Hydroponic Ginger & Turmeric Production
Bored with growing tomatoes, peppers, and lettuce? Try growing spicy rhizomes!
Ginger and turmeric are members of the Zingiberaceae family of tropical and subtropical plants. They are well-suited to protected cultivation in a warm, humid environment with plentiful nutrients and moisture-retentive substrate beds.
Fresh rhizomes of ginger and turmeric have long been recognized for their culinary properties. They provide a slightly different, more aromatic flavor profile than their dried counterparts, owing to the presence of volatile compounds that are released when the rhizomes are cut or grated.
Aside from their use in edible dishes, ginger and turmeric both have several medicinal uses, with fresh ginger used to alleviate nausea, while turmeric has long been used for its digestive, antioxidant, and anti-inflammatory effects. Turmeric contains many powerful compounds, including different curcuminoids and volatile oils like zingiberone, turmerone, and atlantone. Ginger contains gingerol, a natural bioactive compound known to have anti-inflammatory and antioxidant properties, as well as be useful as a digestive aid and as an antibacterial agent.
Along with these medicinal and culinary properties, a well-developed ginger or turmeric plant provides a lush, tropical feel to any indoor garden, with their large, lime-green, attractive leaves. Turmeric plants also have the advantage of producing beautiful exotic blooms if conditions are conducive to rapid growth and development.
Growing ginger and turmeric hydroponically ensures the rhizomes can be harvested at any stage. Fresh, young ginger rhizome has a crisp and juicy texture that lacks the fibers of older rhizomes. Its flavor is subtle and ideal for slicing thinly to eat raw or to make into pickled ginger for use in Japanese cuisine. Fresh turmeric has a mild, earthy flavor, and a finger-staining, intense yellow color that is often used as a natural dye. Young harvested turmeric rhizome can be used immediately, grated into curries and other dishes, or blended with fruit and vegetable juices to create a supercharged smoothie. The harvested rhizomes may also be air dried and will keep for many months before replanting for the next crop or being consumed.
Ginger & Turmeric Propagation
Ginger and turmeric are surprisingly easy to propagate from rhizomes purchased from the supermarket, specialist Asian grocery market, or online. Both are sold as fresh rhizomes, although they may have been in storage for several weeks to months before sale. In this dormant state, the buds present on the sides of the rhizomes remain relatively flat and difficult to see. Once conditions become sufficiently warm, these buds start to swell. Small buds forming on ginger rhizomes kept in a warm kitchen after purchase are common, but turmeric often needs to be sprouted under warm and moist conditions before the young sprouts will form and become large enough to see.
Turmeric contains plenty of buds on the sides and ends of the rhizomes, and even old and dried up rhizomes can spring back to life once planted out into moist substrates. After obtaining fresh rhizomes, they can be broken into fingers or side shoots to increase the number of plants obtained from each—even small sections of rhizome usually contain at least one bud that will form a new shoot and young roots once planted.
Optimal growing mixes during the propagation stage are sterilized perlite, vermiculite, coconut fiber or rockwool, which helps retain moisture but at the same time won’t become oversaturated, which can encourage rhizome root. Pieces of rhizome are pushed into the growing substrate in a shallow tray to a depth of around two inches with any visible buds facing upwards. The tray is then best placed on a heated propagation mat or pad to speed up the rate of shoot formation. Ideal temperatures surrounding the rhizome pieces are around 82-90 oF in the growing media at this stage. Buds should start to swell and grow along the sides of the rhizomes within two to four weeks, and as they emerge, young roots will form around the base of the shoot.
The First Shoot
After the first leaf has emerged and unfurled, the sprouted rhizome can be transplanted to a larger container or growing bed and the first application of dilute nutrient solution applied. As the rhizomes are developing the first shoot, a moderate level of light that is typically used in a propagation area for clones and cuttings can be used, with a relative humidity level of 80 to 90 per cent. Because the plants produce an underground crop of rhizomes, a soft, friable, moisture retentive growing substrate is ideal. Coco fiber fines mixed with 20 per cent perlite or a vermiculite/perlite mix is ideal, although the plants are quite adaptable to a range of other substrates. Large pots, buckets, and beds are ideal, provided the depth of substrate is at least 12 inches to allow for the large size of the root system at plant maturity.
Hydroponic Systems & Growing Conditions
Drip hydroponic systems are most suitable for growing ginger and turmeric, and these heat-loving plants will happily grow alongside tomatoes, capsicums, cucumbers, melons, and other fruiting plants because they have similar nutritional requirements. Once ginger and turmeric plants have two to three leaves, light levels can be increased to full strength, with similar intensities as many other high light crops grown in indoor gardens. While shading can be tolerated and doesn’t detract from the attractive nature of the foliage, it does reduce rhizome yields and increases the time to harvest. Ginger plants are best mounded up as the rhizomes develop. Mounding refers to adding more growing medium around the base of the plant, which helps increase yields and quality of the harvested product.
Day length is not an issue with these plants, but they do need warmth with optimal levels of 72-86°F, although both will happily grow at temperatures higher than this. Cool conditions will slow or prevent growth, so these plants are ideal candidates for growing outdoors in summer and bringing inside to overwinter and continue producing in winter in the tropical heat and light of a well-lit indoor garden.
Ideally, ginger and turmeric prefer humid conditions of 70 to 90 per cent. By growing them in large, densely planted clumps, they can create their own micro climate of humidity, and this, combined with a damp growing medium, tends to lead to optimal growth. Low humidity will cause the lower, older leaves to develop slight tip burn, which can be trimmed if necessary. Placing ginger or turmeric plants in the most humid area of an indoor garden is the best course of action.
General-purpose nutrient solutions at an EC of 2.2-2.6 can be applied to ginger and turmeric crops. However, switching to a fruiting or bloom formulation at a higher EC seems to assist with intensifying the flavor and aromatic profile of the rhizomes. Your pH levels are best maintained around 5.7-5.8 to maximize nutrient uptake.
Reaching Maturity & Harvesting Ginger & Turmeric
While both plants are long-term crops, turmeric will produce harvestable rhizomes more rapidly than ginger plants. Under ideal growing conditions, with sufficient heat, the first small turmeric rhizomes grown hydroponically can be harvested in as little as six months, with main crop yields taking around eight to nine months. Ginger can also be harvested relatively young and small; however, full-sized, large rhizomes can take anywhere from 12 to 18 months from planting.
Ginger plants at maturity are generally larger than turmeric, although this depends somewhat on variety and growing conditions. Ginger plants should be spaced 18 inches apart, and turmeric plants 12 to 14 inches apart, provided light levels are sufficiently high. This will give a dense canopy of foliage that makes a tall backdrop for smaller ornamental foliage and flowering plants in amenity plantings. While the flowers of culinary ginger are insignificant and not particularly attractive, turmeric blooms are delightfully exotic, won’t affect rhizome development, and are even edible, so these alone are worth growing the plants for.
Harvesting ginger and turmeric is relatively simple. Turmeric plants will develop foliage yellowing and dieback once the rhizomes are fully mature. Plants can be harvested before this stage as young rhizomes are tenderer and fully usable, but they won’t store for extended periods of time. Plants can be pulled from the growing substrate, which has been allowed to dry down for a few days, and the rhizomes plucked from the root system.
Alternatively, a rhizome or two can be generally removed form the plant while it is still growing by digging down around the base of the stem and removing the largest that has formed, then replacing the substrate. The plant will continue to direct reserves into the remaining rhizomes, allowing a longer period of fresh rhizome harvest. Once harvested, the skin on ginger and turmeric rhizomes is so thin it can be gently washed before immediate use. For longer term storage, they require air drying to cure the outside layers of the rhizome or stored wrapped in plastic under refrigeration.
Under optimal growing conditions, ginger and turmeric are relatively hassle-free crops and seem remarkably immune to common exotic plant problems such as root rot or die back due to overwatering. They can, however, suffer from common pest issues. With an indoor garden or greenhouse these typically include fungus gnats during the propagation phase, and mites, thrips, and whiteflies on more mature plants, which can all damage and discolor the foliage rapidly.
Early identification and control of pests is recommended, and the large, dense canopy may also provide a suitable environment for the use of integrated pest management (IPM) with introduced predator and parasite insect controls. The foliage of turmeric can be prone to spray damage from the regular use of insecticide oils, so these are best avoided unless plants are close to harvest maturity when leaf marking is less of an issue.
While ginger and turmeric may be familiar as dried spices readily available in pre-packaged form, the young rhizomes freshly harvested from a hydroponic garden provide a more powerful punch when it comes to flavor and bioactive compounds. They are also fun and attractive to grow, so why not shake things up this year and give it a try?
Written by Lynette Morgan | Author, Partner at SUNTEC International Hydroponic Consultants
Dr. Lynette Morgan holds a B. Hort. Tech. degree and a PhD in hydroponic greenhouse production from Massey University, New Zealand. A partner with SUNTEC International Hydroponic Consultants, Lynette is involved in remote and on-site consultancy services for new and existing commercial greenhouse growers worldwide as well as research trials and product development for manufacturers of hydroponic products. Lynette has authored five hydroponic technical books and is working on her sixth.