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This is confusing me since I am new to the idea of hydroponics. I have read that it is possible to damage a plant by overwatering it, so how can plants live with their roots submerged in pure water? Is it only possible to grow specific plants using hydroponics? Or is there a large misunderstanding regarding overwatering?

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Given the previous answer, which covers hydroponic growing, I'll just add an explanation of how it's possible to over water a plant which is growing in potting compost, and thereby cause plant death or disease.

The key is in the word 'clean' - hydroponics requires clean water, principally. When a plant has its roots in soil or compost, this isn't clean in the same way. The planting medium is full of bacteria, fungal spores and a wealth of other micro organisms and bio diversity, most of which are supportive of the plant's growth. If you leave this pot with its plant sitting in water permanently, the conditions in the soil change, usually from life supporting to toxic in some way. Gas exchanges are affected, some bacteria multiply and others simply die, and fungal spores may overgrow, thus providing a very toxic environment for the plant trying to survive with its roots in that soil. This is not true of all plants - some grow very well in soggy, wet soil, but the vast majority do not.

  • So, youre saying it is possible to overwater the soil but not the plant itself? – Nick Apr 9 '13 at 21:41
  • Well you could say that, but its not entirely accurate - the roots of the plant are in the soil, ergo, the soil is overwatered and so are the roots, and obviously, the plant. You could overwater, then empty out the water or drain it, and the plant wouldn't be overwatered - leave the water, without emptying or draining, and the plant will become overwatered, with the definition of 'over watered' for the plant being suffering ill health/death. As I said in the answer, its the growing medium which makes the difference. – Bamboo Apr 10 '13 at 11:44
  • Then how is it possible to grow plants in pure water? – Nick Apr 10 '13 at 19:47
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    I just realised why you're confused, but you need to re read the second part of my answer, which explains why permanently wet soil is toxic to most plants, whereas clean water on its own, with a few nutrients added, is not. – Bamboo Apr 12 '13 at 10:40
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    Hydroponics requires aerated water. If you leave a terrestrial plant sitting in stagnant water, then the oxygen is consumed and then the roots become hypoxic as the water is not being refreshed with new water containing oxygen. – Graham Chiu Jan 10 '16 at 1:37
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It is possible to overwatering plants, when their stems (being into soil) get too much water and no light. In fact, most of the problems of plants comes from an error in the relationship between water and lighting.

The hydroponic cultures can be made in two ways.

  • The plant (or rather, a cutting of a plant) is partially immersed in water in a transparent glass container, where it get new roots. look at the picture into answer
  • A plant, with already its roots, is introduced into a special container, where it is not in contact with the water and, through a grid, reaches the water only with the roots.

casa vaso http://www.wikinoticia.com/images2//www.jardineria.pro/wp-content/uploads/2012/04/hidro1-400x300.gif

In the first case, the stem enters the water that stimulates the production of roots. But the stem in contact with the water rots, little by little, so that it must be periodically cleaned, ie removed from the container and washed under warm running water. Then put back into the container with clean water. The roots must receive plenty of light. The light, however, also contributes to the formation of green algae that suffocate the roots and remove the light itself. For this reason, plants, containers and water should always be kept clean, as in aquariums.

In the second case the stem does not touch the water. For the roots to be immersed in water or not makes no difference. And light is not so necessary. Then the containers can be colored (but transparent, in any case).

The water, in both cases, must always be very clean. The food is provided by special fertilizers. The hydroponics is easy and comfortable. It is very hard to wrong and, vice versa, it is easy to correct the errors.

Not all plants can be grown hydroponically. Of course not all succulents and plants that do not bear a lot of watering. The house plants, however, are almost all suitable to give cuttings to grow in water. Indeed they are mostly tropical plants from rainforests, rich in water. Although almost all plants of industrial agriculture are arable with this method.

Salad hydroponic on roofs of New York (here, not translated) k

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    I don't think this is true. In aquaponics the water is certainly not "very clean". The essential thing is that the water is oxygenated otherwise the roots will drown. – Graham Chiu Jan 12 '16 at 2:57
  • @GrahamChiu Oxygenated water to me means movement and constant replacement and very very clean. Only NECESSARY chemicals are added versus 'food for the plants'...This is fascinating. What is the definition of CLEAN? I've always thought that in aquaponics the water was MOVING to enhance oxygenation and not allow any organic thing to reproduce, such as algae. In fish tanks, I know this stuff well, we have ways to keep the water oxygenated and moving with bubblers. Changing the water is critical. Testing the pH is a big deal. Wish I knew more and looks like I am going to be learning more... – stormy Dec 22 '16 at 22:17
  • @GrahamChiu Is this article sounding reliable? I just now! learned the difference between aquaponics and hydroponics. Wow. Aquaponics uses the water that fish live and poop in. Let's call this water, dirty. Aquariums use all kinds of chemicals to maintain. Is there a feedback system to the aquarium? Using some of these chemicals requires GLOVES. I drew the line at most. Where should the water be sourced? TAP? I now know that hydroponics is without FISH. Just plants, correct? – stormy Dec 22 '16 at 22:25
  • homeaquaponicssystem.com/basics/… – stormy Dec 22 '16 at 22:25
  • I think that article is biased. Many places can't do aquaponics because there's no suitable fish for the climate available. Fish food may not be sustainably sourced, eg. Slave labour on fishing boats. Most aquariums don't use any chemicals. Just fresh water. Tap water is usually fine once it's been dechlorinated. – Graham Chiu Dec 22 '16 at 23:51

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