How can I kill a plant by overwatering it, yet propagations of the same plant will grow in water?
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Roots need oxygen in the same way leaves need carbon dioxide.Soil is porous and roots absord oxygen from the spaces in the soil. Too much water can cut off the supply of oxygen to the roots ( roots need O2 from air ). Some water if fine as long as it is aerated.Too much water and the plant goes to live on a farm with all the other overwatered plants.
Overwatering is not about the amount of water, it’s about the frequency of waterings, In fact you can literally inundate most common houseplants in tons of water and they’ll be completely fine as long as you let them dry thoroughly afterwards. If you keep the soil damp all the time, not letting it dry up properly between waterings, it will grow bacteria and molds which will suffocate the roots and kill off those delicate root hairs, making the plant unable to suck up water, which will ultimately kill it. This is not a problem in water simply because the lack of soil prevents molds and bacteria from building up.
Roots that develop in water are different from roots that develop in soil. https://www.yourindoorherbs.com/differences-between-soil-roots-water-roots/
The water isn’t what’s killing the plants, the constantly-moist soil promoting rapid fungal and bacterial growth, and/or constantly washing nutrients out of the soil and starving the plant is what kills them.
If someone was drowning all your food in water for a couple of hours before serving it to you, you’d have much the same issues.
It’s usually not the water that’s the problem, it’s the mold and bacteria that grows when the soil is damp for long periods of time.
Mold and bacteria need water, oxygen, nutrients, and surface area to grow.
In soil, there’s nutrients and oxygen readily available and a lot of surface area to promote growth. Damp soil provides the water.
Letting the soil dry out between waterings dries the mold/bacteria out, killing off most of it and keeping bacteria growth under control.
In a glass of water, there’s not much nutrients and oxygen, and also importantly very little surface area. Only the surface of the plant roots are available for bacteria growth. A full-water environment doesn’t make for ideal bacteria growth conditions.
Changing the water once a week or two can keep algae growth down, and that’s easy enough.
Mold cannot grow submerged in water because it needs sufficient oxygen to survive, but mold can grow on the surface of water if there are enough nutrients for it. When you overwater a potted plant, you create soil that is damp but still breathable and full of nutrients, the perfect environment for mold.
Fun fact: This is the principle behind brewing and fermenting. Anything properly submerged in liquid remains safe to consume because you create an environment that is inhospitable to mold, mildew, and most bad bacteria.
Roots need oxygen. Overwatering in a pot displaces the oxygen in the spaces of the soil by oversaturation of the water table.
Oxygen exchange improves as the water surface is increased (like in a jar) and with agitation. In a regularly changed jar of water the plant will have better oxygenation at the root zone compared to an overwatered pot with low drainage.
It’s not the water that’s so much the issue, it’s the growth of bacteria, mold and all that fun stuff that hurt the roots. The germs (when they get to “hungry” in the sense think “let’s eat this big thing! It looks tasty” and then they eat the roots.
In plain water, it’s a lot harder for bacteria to live and be fuckin, but they still are. That’s why the propagation water should be changed every 2-3 days.
The plant can be fine in straight water, because it will move energy that would be used for growing leaves and bigger, down into growing roots to get nutrients.
I am guilty of this. Killed a peach tree last year, never could figure out why in spite of watering it daily. What about in places like Costa Rica during the rainy season where it rains every day, why dont the plants die out there?
I do aquaponics. Roots need to breathe also. If you are growing in just water, you need to aerate the water either by circulating or using an aquarium bubbler. Soil is like a sponge. If you water too much it doesn’t allow enough air for roots to breathe. If you have proper drainage, allow the soil to dry some or have a medium that doesn’t pack as tight as soil, roots can breathe
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