Something Old, Something New: New Crops for Hydroponics

Trying a new crop in your hydroponic system is always exciting, especially if it’s something fresh and exotic and equally delicious.

Plant breeders are continually coming up with new cultivars, but some of the most interesting new prospects for hydroponics are actually ancient crops with great potential for indoor gardens. Here’s a few new crops to try at home.

How to Grow Hydroponic Salanova Lettuce

One of the most exciting new crops for hydroponics is salanova lettuce types, a recent innovation from Rijk Zwaan seeds in the Netherlands, which can now be purchased by home growers.

Salanova lettuces are unique because they produce a full-sized, mature lettuce head that consists of baby-sized, uniform leaves. The core of the Salanova is removed with a specially designed corer and the lettuce head falls into numerous small, tender leaves.

The Salanova range includes red and green butterhead, oak leaf, incised leaf and green frisee lettuce. These lettuces are fast growing and uniform under indoor growing conditions, as they were largely bred for indoor production.

Salanova lettuce can be grown alongside traditional hydroponic lettuce types and the plant is particularly well-suited to nutrient film technique, aeroponic and solution culture systems.

Seeds are best raised in soilless propagation cubes to prevent any transplant shock. A well-balanced, grow hydroponic nutrient at an EC of 1.8 to 2.4 mScm-1, combined with additives such as silica, humic and fulvic acid products all assist with production in NFT systems.

Adjusting the pH with a high-quality pH down solution to between 5.8 and 6 and checking the nutrient solution temperature under warm growing conditions are all vital for lettuce production.

Ideal nutrient solution temperatures for lettuce are cooler than other crops—around 57 to 66°F. This crop benefits from installing nutrient chilling equipment for summer growing.

How to Grow Hydroponic Oca and Ulluco

Of the ancient crops that adapt well to hydroponics, there are a couple of tuber-producing plants that can provide an exotic and different taste sensation to meals.

These are oca (Oxalis tuberosus) and ulluco (Ullucus tuberosus), both staple tuber crops from the highland areas of the Andes. Ulluco produces strikingly colored tubers in shades of yellow, pink, purple, red, spotted and striped with a taste and texture similar to that of a new, waxy potato with slightly nutty overtones.

Oca produces rounded or long cylindrical tubers that range in color from white to deep purple and red, and the flavor of the flesh is slightly tangy and starchy when fully cooked.

Both ulluco and oca are small, easy-to-grow plants propagated from tubers, which are left to sprout, like potatoes, then sown into a suitably friable and free-draining hydroponic grow medium.

This is one area where hydroponic growing has a major advantage, as these tuber-producing crops thrive in a well-balanced and blended soilless substrate, which not only enhances nutrient uptake and growth, but also helps the development of large, uniformly shaped tubers.

Suitable mediums for root crops include many of the top-quality coco coir products specifically designed for hydroponics, some of which have been pre-blended with beneficial microbes, organic additives and perlite. Coco coir and perlite mixtures in 70:30 and 50:50 ratios are also ideal.

Suitable hydroponic systems for small tuber crops are usually drip irrigated with a substrate depth of one foot or more.

Hydroponics retailers can provide advice on the best type of hydroponic system and equipment for growing root crops, including the right selection of indoor lighting, both in terms of intensity and spectrum.

Tuber crops, like many other plants, benefit from balanced, full-spectrum lighting with some enhanced UV output.

Both oca and ulluco plants require warm growing conditions (60 to 77°F) with a low to moderate EC (1.0 mScm-1) and a general-purpose nutrient solution.

Plants grow steadily for a few weeks and then require a shortened photoperiod of 12 hours per day to initiate the production of new tubers, as would naturally occur in autumn outdoors.

Under these conditions, ulluco produces stolons (stems originating from the leaf axils) that penetrate the soil, and tubers are formed at the end of these stems.

Ulluco is also a dual-purpose crop, as the foliage can be eaten, steamed or boiled similar to spinach. After harvest, oca and ulluco tubers can be stored in the same way as potatoes, and steamed, boiled and baked before eating.

How to Grow Hydroponic Elephant Garlic

Elephant garlic (Allium ampeloprasum) is another novel crop fairly new to hydroponic production. It can produce spectacularly huge and tasty bulbs and is much more productive than standard garlic.

Elephant garlic is not actually true garlic, but a leek variant. Its flavor is milder than garlic and often more palatable when used raw. The bulbs can grow to enormous dimensions (up to a pound in weight), making this a productive hydroponic crop for media bed systems.

For planting material, the individual cloves are separated and sprouted in water for one or two days until green shoots appear.

These are planted into a suitable substrate such as pre-conditioned and pre-blended coconut fiber, coco coir perlite mixes, rockwool or organic mediums and grown in a similar way to other onions.

The grow medium for these types of bulb crops can also be inoculated before planting out the garlic cloves with products containing blends of microbes such as trichoderma, mycorrhizae and other beneficial bacteria.

The substrate should be well saturated with water once in place in a warm growing area, then inoculated with products containing these beneficial microbes and left for a few days to allow populations to establish and colonize the growing medium.

Once the garlic cloves have been planted, these beneficial microbes can help to suppress any rot pathogens that are a risk during the first week or two of establishment.

If fungus gnats become a problem during the development of the garlic crop, the surface of the grow medium can be covered with either black plastic film, chunky perlite or a recycled glass product developed specifically for gnat control.

Elephant garlic needs a long, warm growing season with a day length of at least 14 hours for bulb formation. The foliage consists of broad flat leaves, similar to a large leek, but the plant remains compact enough for indoor gardens and can be grown at a high density.

How to Grow Hydroponic Peanuts and Water Chestnuts

Some other old crops that are new to hydroponic cultivation include peanuts and water chestnuts. The peanut plant (Arachis hypogaea) is a legume species in the bean and pea family that can be sprouted and grown under warm, high light (full-spectrum artificial lighting) conditions until they flower.

The small, bright yellow flowers of the plant will then produce pegs—stems that grow and burrow themselves in the grow medium. Young nuts form below ground in their shells at the tips of these pegs.

One of the main issues with growing peanuts, even in soilless systems, is fungal pathogens attacking both the germinating nut and later the young plant.

Because of this sensitivity to disease attack, growers should inoculate with trichoderma-containing additives throughout the plant’s growth cycle and watch carefully for any signs of disease. Fungicides are an alternative for use during the germination phase.

Using a free-draining growing medium and restricting nutrient solution application to keep the root zone slightly dry is also important with this crop to help prevent root rot pathogens. Substrates such as a 50:50 coco coir to perlite pre-mix growing medium are ideal for this. Peanuts might not be that productive on a small scale, but they are a fun and novel crop to try.

Chinese water chestnuts (Eleocharis dulcis) are semi-aquatic plants and thus well-suited to hydroponics. They are also a delicacy and eaten fresh are a tasty alternative to the tinned variety commonly used in Asian cuisine.

The edible chestnut is a white-fleshed, crisp and crunchy corm with dark skin on the stolon root system of a small reed-like plant that thrives in nutrient-rich, warm water on the edges of ponds.

Ebb and flow, deep flow solution culture, pond systems and even aeroponics can be used to grow water chestnuts.

Good results have also been obtained with the flood and drain type hydroponic set-ups where the system doesn’t completely drain during the ebb cycle so that the plants are always sitting in a shallow depth of nutrient solution (1 to 2 in.), but also receive fresh oxygen and nutrients with each cycle.

Young water chestnut seed corms are initially planted in a substrate that will hold the corm firmly in place while it develops a strong root system to anchor the plant.

Any substrate that does not float is suitable, including some grow rock products, pea gravel and rockwool cubes.

Nutrient solution is run at an EC level of 0.5 to 0.8 mScm-1, starting with a grow nutrient formulation product and switching to a bloom product as young corms start to form. The addition of silica-containing nutrient additive products is often beneficial for this type of aquatic plant.

Once established, water chestnuts require a warm (78 to 89°F) growing period of around six months and high light levels as the reed-like foliage develops, followed by the production of stolons and new corms.

At harvest, the hydroponic system can be completely drained and the water chestnut corms collected, saving any smaller corms as seed for the next crop.

Alternatively, larger corms can be harvested by carefully rummaging around under the growing plants as they reach a sufficient size and the plant left to grow and crop year-round.

Water chestnuts grown hydroponically have less pests than those grown outdoors in ponds where slugs, snails, ducks, fish and other predators can take their share of the crop, but they can develop the usual run of garden pests including aphids and mites.

Spray applications of neem or pyrethrum-based products are usually effective against most insect pests and will not harm the water chestnut plants.

Hydroponics is a great tool for trying new crops or even reinventing old ones into a modern-day gourmet garden with a unique, but productive edge.

Most plants adapt well to soilless culture provided the correct type of hydroponic system, grow medium and environment are provided, so some research into the requirements of those lesser-known crops is a good place to start. Information coupled with some experimentation leads to a rewarding experience.

Read More: Hydroponics: Pros and Cons of Hydroponic Gardening