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Hydroponic farming: More on growing leafy vegetables

We look at more leafy vegetables that are suitable for closed systems.

It is very important that a thorough economic viability study be done before a crop is planted to make sure that the market to be supplied is also viable.

Crops grown in tunnels should achieve higher prices on the market than the same crop grown in the open field.

Hydroponics is used to ensure that a better quality crop is produced, and the price must complement the quality.

SPINACH or SWISS CHARD?

When we talk about “spinach” (Spinacea oleracea) in this article, we mean Swiss chard, which looks a lot like “true” spinach, but has much broader leaves, thick stems and contains more vitamin A.

  • Spinach is an annual plant cultivated for its succulent, nutritious leaves.
  • It contains considerable quantities of minerals and is rich in iron, sodium, calcium, vitamin A and B2.
  • Researchers have found, however, that the calcium in spinach is available in the oxalate form, which is not very healthy, especially for children.

As a result, and also because the yield is low, cultivation of Swiss chard (Beta vulgaris L var cycla (L) urich) has become more common. It belongs to the beetroot family, and is often incorrectly referred to as spinach.

CLIMATIC REQUIREMENTS AND GROWTH PERIOD

  • Swiss chard is a cool weather crop with optimum temperatures of 16°C to 24°C.
  • The period from transplanting from seed trays to harvest is 35 to 45 days.
  • Leaves can be harvested for approximately 80 days, but once the stem becomes too long, the quality of the leaves declines.

SPACING

  • Spacing in the GFT system is 200 mm x 200 mm to 250 mm x 250mm.
  • Most spinach cultivars have a flat, open growth habit.
  • If you want to force these cultivars to grow upright, plant them closer together.

Also read: Hydroponic farming: The basics – popular systems

COLE CROPS

  • The cost of producing cole crops (cabbage, cauliflower, etc.) hydroponically limits its potential to high-value products such as baby cauliflower and Chinese cabbages.
  • Cole crops are extremely sensitive to deficiencies of the 2 trace elements, molybdenum and boron.
  • These elements can be applied to seedlings as a foliar spray about a week before transplanting.

CHINESE CABBAGE

  • There are 2 types of Chinese cabbage, Pe-Tsai (Brassica pekinensis) and Pak-choi (Brassica chinensis).
  • The Pe-Tsai group has loose, curly, rectangular leaves that don’t form heads.
  • Pak-choi produces loose leaves, like Swiss chard.
  • The flowering Pak-choi (Brassica parachinensis) is grown for its thick-stemmed flowering shoots and leaves.
  • Chinese cabbage came from East Asia and is preferred to the ordinary cabbage in Asia.
  • Flowering Pak-choi is particularly popular in Hong Kong, and is harvested as soon as the yellow flowers start to open.
  • Chinese cabbage is mainly used in salads and soups, but it can also be used in stir-fries and stews.
  • Pak-choi and flowering Pak-choi can be cooked in the same way as Swiss chard, and tastes more or less like spinach.
  • Various cultivars of Chinese cabbage are available and seed companies will advise the producer in selecting the best cultivars.
  • They may also identify which cultivar is preferred by the consumer.

CLIMATIC REQUIREMENTS

  • Chinese cabbage prefers relatively cool climatic conditions.
  • The optimum temperature is about 19°C, with a range between 9°C to 25°C.

GROWTH PERIOD

  • Some cultivars can be grown throughout the year, and some are ready for marketing in about 60 days.
  • Growth declines considerably when night temperatures drop below 2°C.

SPACING

Chinese cabbage comes in different sizes and shapes, so ask your seed merchant for the correct spacing for the cultivars you have chosen.

HERBS

  • Hydroponic herb production is fairly easy.
  • Several kinds can be grown in hydroponic systems, including parsley, basil, chives, mint, oregano, sage, thyme, watercress and mustard.
  • Some herbs are perennial, and their roots develop vigorously within a few months.
  • When the root mat becomes too thick, replace the herbs with a new crop.
  • Seedlings are usually grown in seedling trays.
  • They are transplanted once they are strong enough and easy to handle.
  • Mint and watercress can be propagated by taking cuttings that can be rooted directly in a medium in pots or in seed trays before transplanting.

Also read:
Hydroponic farming: How to produce vegetable seedlings
Hydroponic farming: Growing lettuce in a closed system

  • This article was written by Erika van den Heever, Martin Maboko and Silence Chiloane and first appeared in Farming SA.

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