Microgreens in hydroponics - what you should know
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Microgreens are seedlings. In other words, young plants in the germination stage. They have the advantage that they do not need fertiliser and can be grown on a moist "mat". Even cereals such as rice, oats, wheat, maize and barley as well as pulses such as chickpeas, beans and lentils are sometimes used for microgreens. They are rich in nutrients and very easy to cultivate hydroponically. A simple, moist growing mat is all that is needed to grow them. Therefore, microgreens are very popular in indoor farming. |
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First an overview of which genera are suitable:
- Brassicaceae family: cauliflower, broccoli, cabbage, watercress, radish and rocket.
- Asteraceae family: lettuce, endive, chicory and radicchio
- Apiaceae family: dill, carrot, fennel and celery
- Amaryllidaceae family: garlic, onion, leek
- Amaranthaceae family: amaranth, quinoa, chard, turnip and spinach
- Cucurbitaceae family: melon, cucumber and pumpkin
Since their introduction to the Californian restaurant scene in the 1980s, micro-vegetables have steadily grown in popularity. These aromatic and nutrient-rich vegetables, also known as micro herbs or vegetable confetti, are rich in flavour and easy to grow.
Get an overview here.
Most of them do not need any fertiliser at all. The seed contains enough to get by on water alone until the first germination. Make sure that the water is slightly acidic. In the range between pH 6 and 7 you often have good results, depending on the variety. Here you will find a guide to pH and Ec values if you do not trust rainwater or leachate alone. In principle, all those useful plants and thus herbs and vegetables can be grown and consumed as microgreens where the leafy greens are edible.
Nightshade plants such as tomatoes and aubergines are not suitable because they contain solanine in their leafy greens and this substance is toxic.
The following seeds are good
Herbs
- Dock (Rumex)
- Anise (Pimpinella anisum)
- Basil (Ocimum basilicum)
- Dill (Anethum graveolens)
- Garden orchid (Atriplex hortensis)
- Chervil (Anthriscus cerefolium)
- Coriander (Coriandrum sativum)
- Mint (Mentha)
- Parsley (Petroselinum crispum)
- Lemon balm (Melissa officinalis)
Vegetables
- Cauliflower (Brassica oleracea var. botrytis)
- Broccoli (Brassica oleracea var. italica)
- Beans (Phaseolus vulgaris)
- Peas (Pisum sativum)
- Strawberry spinach (Blitum virgatum)
- Fennel (Foeniculum vulgare)
- Spring onion (Allium fistulosum)
- Carrot (Daucus carota subsp. sativus)
- Chard (Beta vulgaris subsp. vulgaris)
- Pak choi (Brassica rapa subsp. chinensis)
- Radish (Raphanus sativus var. sativus)
- Beetroot (Beta vulgaris)
- Red cabbage (Brassica oleracea convar. capitata var. rubra)
- Rocket (Eruca sativa)
- Celery (Apium graveolens var. dulce)
When the microgreens are ready to be harvested, they should be processed quickly, as they quickly begin to rot. Unfortunately, microgreens are also not well suited for freezing and lose some of their healthy ingredients in addition to their crunchy texture.
Mould could form when growing microgreens, as a certain level of moisture is important. If you notice mould on your microgreen crop, you should compost it directly and not consume it under any circumstances.
The health aspect:
Nutrient content varies slightly, but most varieties are rich in potassium, iron, zinc, magnesium and copper (1). Microgreens are also a good source of beneficial plant compounds such as antioxidants (2).
In addition, their nutrient content is concentrated, which means they often contain more vitamins, minerals and antioxidants than the same amount of mature greens (3).
Research comparing microgreens to mature greens has found that the nutrient content of microgreens can be up to nine times higher than that of mature greens (4).
Research also shows that they contain a greater variety of polyphenols and other antioxidants than their mature counterparts (5). In one study, the concentrations of vitamins and antioxidants were measured in 25 commercially available microgreens. These values were then compared to those recorded in the USDA National Nutrient Database for mature leaves.
Although the levels of vitamins and antioxidants varied, the levels measured in microgreens were up to 40 times higher than those recorded for mature leaves (1).
However, not all studies come to similar conclusions.
For example, one study compared the nutrient content of sprouts, microgreens and adult amaranth plants. It was found that the adult plants often contained as much, if not more, nutrients than the microgreens (5).
So although microgreens generally appear to have a higher nutrient content than mature plants, this can vary depending on the species.
Sources
1) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5362588/
2) https://pubmed.ncbi.nlm.nih.gov/22812633/
3) https://www.sciencedirect.com/science/article/abs/pii/S0889157514001513
4) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3915300/
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