How come many houseplants will rot if their roots sit in waterlogged soil but when you propagate plants you let the roots sit in water to grow?


How come many houseplants will rot if their roots sit in waterlogged soil but when you propagate plants you let the roots sit in water to grow?

In: Biology

This is because of the presence of bacteria and other micro organisms in soil. Usually the soil is well aeriated but when it becomes water logged, the organisms start to compete and start to eat other competitors. That’s why the roots start to rot.

Hope this helps.

Also, if the presence of water is too much, and very little is used, then it forms a hypertonic condition in the roots and this causes the cell walls of the cells in the roots to break and causing the lysosomes to release chemicals ( I don’t exactly remember which) which break down the rest of the cells in the roots. This could also be a reason. I just remembered this.

You are supposed to change the water every few days when growing roots. Also, water by itself is less of a breeding ground for anaerobic bacteria as there’s less nutrients and more gas exchange.

If there’s water sitting in your soil, there’s basically zero gas exchange, so oxygen will deplete and anaerobic bacteria will thrive.

Waterlogged soil is anoxic – there is no oxygen for the roots to “breathe”, so the cells die and are consumed by soil microbes. Additionally, the roots which plants grow when cut and placed into water are slightly different than “soil roots” and are designed for metabolism in water rather than an aerated medium.

As been mentioned, it is due the the presence of oxygen in the water. Plants require oxygen for cellular respiration,, and obtain most of that oxygen through their roots. Standing water becomes anaerobic, meaning there is little if any oxygen in the water. So long as water is oxygenated, most plant can grow with roots completely submerged. This is how plants are grown hydroponically.

Plants need oxygen within the water and when they eat all of it out of the water then they will slowly starve. Hydroponics gets around this by constantly pumping oxygen into the water so it stays “fresh”

And to add on to all the points about bacteria that people have been making there’s also an abundance of beneficial bacteria.

I’m an amateur at some hobby hydroponics and one of the things that I’ve learned now the semi-hard way is that you can’t fight nature but you can harness it.

My most recent crop I nearly lost due to trying (and failing) to fight some sort of infection with peroxide and similar disinfecting agents. I talked to some more experienced hydroponics growers and ditched the h202 in favor of a concentrated beneficial bacteria product; In a week I went from literally losing all the protruding roots and nearly losing the plant to having almost the most root mass I’ve ever seen in plants this young.

It massively out competes the damaging bacteria in my reservoir *and* does a lot to help the plant grow stronger and faster.

I do hydroponics / aeroponics with plants, but mind you: only as a hobby. This is a hobbyists explanation. (Initially wrote this as a reply, but then decided it might stand on its own? You decide.)


Root rot is also a risk when you are “only” using water / a nutrient solution. Root rot is partly caused because the roots do not get enough oxygen, and partly can be / is caused by bacteria.

To keep the risk low, you keep the temps of your nutrient solution low and blow lots of air through it, using air stones like from aquariums. You can also add a bit of H2O2 to help keep your nutrient solution free from bacteria causing rot. At the same time this increases oxygen levels in your solution to prevent the roots from “suffocating”.


You CAN hang your plants directly into the reservoir / the nutrient solution, this is called “Deep water culture”.

Or you hang them into a container or pipe of some sorts and spray or drip your nutrient solution onto the roots, then let it flow back into the reservoir and repeat the cycle.

There is also a technique called “Ebb and Flow” which basically means you flood the plant roots with nutrient solution completely, then let it flow back into the reservoir and give the plant roots some time to dry off. Repeat cycle.

Plants develop “water roots” that require less oxygen. Soil roots cannot extract oxygen from water like water roots and those already developed soil roots will rot. Propagating stems in water promotes water roots to form, which can handle being submerged. You can then plant the cutting with water roots into soil and they sort of turn into soil roots. That’s my understanding anyway.

I know that bacteria and mold has something to do with it. I grow marijuana using deep water culture, the plant sits in clay balls and the roots grow down into a bucket of water. Soil can grow bacterias and house insects, but by using a black bucket that doesn’t refract light then mold cant grow. I also put bubblers in the buckets to create movement, which also stops algae. Just to be clear, im an idiot, I dropped out of highschool and grow weed. Don’t take what i say as gospel.

I’ve got two pretty plastic pots for plants, but they don’t have the little holes at the bottom or anything to allow water to escape. Should I use different pots? I guess these are made for different kind of plants or something?

Hey, horticulturalist here. When you’re propagating in water, or growing something hydroponically, you don’t have any of the yucky soil germs or bugs that lead to rot. Rot isn’t just the plant getting too wet, it’s the bacteria and fungus in that pot that eats away at it.

If you propagate in soil, rot’s pretty much the most common problem you’ll get.