I’ve touched on this topic a couple of times in other aerial roots articles, but I thought the whole ‘aerial roots in water’ deserved its own moment in the spotlight.
There’s a lot of misconceptions about what happens when you put aerial roots in water, and all the advice out there is pretty polarising.
It’s either ‘Try this one LIFE-CHANGING hack to DOUBLE your Monstera leaves overnight!!!’
Or, of course:
‘This one Tik Tok hack will KILL your Monstera in TWO WEEKS’
The reality is, of course, actually a bit more nuanced and, er, boring.
It also errs MUCH closer to being a growth hack than a sick, Monstera snuff trick dreamt up by sellers to double Monstera sales.
What happens if you put an aerial root in water?
When you put an aerial root in water (or any other substrate), it starts to change its physiology. Botanists haven’t cleared up all the hows and whys of this, but the basic idea is that it’s no longer an aerial root.
An aerial root has a specific function: it anchors climbing plants to whatever they’re climbing up. They can also absorb nutrients and moisture.
When you put an aerial root in water, it will start to change into a subterranean root, and play a much bigger role in absorbing nutrients and moisture.
We’re not 100% sure how they do this, but submerged aerial roots produce fewer raphides, which are calcium oxalate crystals that help the plant defend itself against predators.
Obvs, the submerged aerial roots won’t need to defend themselves (because they’re underground/water which explains why they don’t need as many, but botanists believe that they also help the plant function as a subterranean root.
Will putting Monstera aerial roots in water make the plant grow faster?
It might. In the short term.
There is a LOT of anecdotal evidence that suggests that putting aerial roots in water does help them to grow faster, and also a bit of science.
HOWEVER
This isn’t really going to change your Monstera dramatically in the long term.
When you put an aerial root in water, it develops the ability to uptake water, and increase the pressure in your plant (called turgor pressure).
It’s a bit like inflating bike tyres – they look rounder when they’re full, and can operate more efficiently, but it’s also not going to make the bike/plant perform significantly better than it was meant to. You’re just getting the pressure right.
If your Monstera is very big, and the new growth is very far away, increasing the turgor pressure can really help you out, especially if you have low humidity so the aerial roots can’t absorb much moisture from the air.
However, if you then take the water away, it’ll just droop again.
I tend to put my aerial roots back into the soil.
Will putting aerial roots in water make them rot?
The aerial root may rot, it’s very unlikely to cause widespread damage unless the plant was weakened to begin with.
One of the main reasons naysayers give for condemning putting aerial roots in water is that it can cause root rot that can spread to your plant.
I would be quite surprised if a rotting aerial root caused root rot to spread throughout the plant, because root rot doesn’t really work that way.
The bacteria thrive in oxygen-less environments, so whilst the root might rot, the bacteria likely won’t survive in any significant numbers more than a few inches away from the water.
If you want to try putting aerial roots in water, sure, there’s a risk to your aerial root, but aerial roots aren’t strictly necessary in your house – you have access to things like zipties, which a Monstera in the wild wouldn’t.
Besides, aerial roots in water rot only rot if you don’t take care of them properly, so there are things you can do to reduce the risk.
How to stop aerial roots from rotting in water
If you’ve read any of my articles on propagation, then the advice is broadly the same: oxygen, oxygen, oxygen.
- Change the water frequently
- Add an air stone/pump – the water movement allows oxygen from the air to dissolve into the water
- Add oxygenating aquatic plants to your water jar – my fave, because I’m lazy (I use java moss). My Thai Constellation lives in water, all her aerial roots go back into the jar she lives in, and I change the water twice a year. Every so often we harvest the moss because it grows pretty well in there
Can you put aerial roots in water to propagate?
Yes and no.
If I were trying to propagate a Monstera, I would probably ‘water layer’ it, by which I mean that I would put an aerial root in water, wait for it to grow roots, and then chop it (just below the node where the root grew from).
HOWEVER
It’s all well and good advising that, but what if the node you want to cut doesn’t have a long enough aerial root?
Well, you can still take a cutting with that small aerial root and propagate it. SOMETIMES, the aerial root will grow into a new root system, but not always. Sometimes roots emerge from the node first. I have no idea why this is.
I don’t have an example of a Monstera cutting to show you, but I recently propped a load of Philodendron brasil in about ten different ways, and the quickest ones to root were the ones in water and fertiliser (GH Flora Grow series).
The roots grew straight from the aerial roots. The next quickest was propped in Superthrive, and the roots came directly from the node.
What I’m trying to impress on you here, is that you don’t NEED an aerial root. Sometimes the plant uses it, sometimes it doesn’t.
Also, experience tells me that how fast cuttings root doesn’t impact how fast they grow new leaves. The one that roots in two weeks may take a year to produce new growth.
How long will it take aerial roots in water to grow?
It varies, but there are things you can do to speed up the process:
- Put the water on a heat mat – roots love warmth
- treat the mother plant very well – the more energy she has, the more she can divert to growing a little supplementary root system
- Increase the humidity of the room – higher humidity is a great way to give plants a tonne of extra energy
There are also a couple of things that might help, but aren’t that thoroughly research:
- Keep the roots in the dark. Root like the dark, and it can encourage them to grow. Wrapping th water jar in black paper is probably the easiest, and perhaps cover as much of the top as you can in tinfoil. Don’t do this if you use aquatic moss to keep the water oxygenated – it’ll need light
- Add fertiliser to the water – a lot of people (including me, actually) recommend not using fertiliser in propagations because it can stress out the plant, but I tried it for funsies, and I can’t really argue with the results. I’ll update if anything catastrophic happens!
Should I put my Monstera aerial roots in water?
It’s entirely up to you. It’s a fun experiment, but it’s unlikely to yield life-changing results.
However, if your Monstera is getting big and droopy, it can be an easy way to perk it up a bit.
Unfortunately, you’ll have to keep the water in place otherwise it’ll droop again, but adding some java moss to the jars means you won’t have to change the water often.
