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Propagating house plants is one of those things that seems so easy, but can simply…not work.
Before the cutting has had a chance to grow roots, it’s rotted past the node.
As an experienced house plant propagator, it can be annoying, but generally, I can tell what the issue is by a process of deduction (nine times out of ten it’s because I haven’t changed the water in four months -_-).
But what about beginners? It can be such a demoralising thing, ESPECIALLY if you’re trying to propagate so-called easy plants like Pothos.
Let me tell you now, there is no such thing as a universally easy-to-propagate plant. No. Such. Thing.
For every ten people that think Pothos is easy to propagate, there will be one poor soul that can’t get that node to explode (I’m not sure if I’m proud of or horrified by that phrase).
Different plants suit different environments (even if we can’t perceive much of a difference) and there isn’t much we can do about that.
There are, however, things we can try to boost our chances of rooting cuttings and stopping our cuttings from rotting before they root.
Why do cuttings rot?
It’s commonly believed that cuttings rot because they’re submerged in water. This is kind of true, but also not at all.
Plants can live in water forever. I keep my Thai Constellation in water, and she’s thriving.
The reason cuttings rot is that over time, the oxygen level of the water drops unless it’s moving or oxygen is added.
Not only do plants need oxygen in order to grow roots (and, indeed everything else), but the bacteria that cause rotting thrive in low-oxygen environments.
So we have a double whammy – low oxygen means no root growth AND bacterial infection (in the form of root rot).
As long as you keep oxygen levels up (and a few other things) your plant won’t rot.
***Leaves will rot if they’re submerged (unless they’re aquatic plants), because leaves will close their stomata when they’re wet, and won’t photosynthesise until they’re dry***
How to stop cuttings from rotting
Sometimes you can just be unlucky. Do all of these things and the cutting will still rot BUT more often than not, good oxygenation and a bit of warmth will work wonders.
Roots really like warmth, because one of the quickest ways to make a cutting root faster is to put it on a heat mat.
Try to keep it at about 24oC/75oF for optimal root growth. Any hotter and you risk the plant going into survival mode and shutting down all operations.
A warm windowsill also works, but studies have shown that roots grow better in the dark, so perhaps wrap the propagation jar in something to block out the light. Obvs the leaves still need light, so don’t put the whole thing in a cupboard.
Increase the amount of oxygen
Lack of oxygen is the main cause of root rot, so oxygenating the water can go a long way to stop cuttings from rotting. There are three main ways to do this:
- Add an air pump
- Change the water every few days
- Add oxygenating plants
Most casual propagators just stick with changing the water every few days. I like to change it twice a week because although once a week will probably suffice, if I forget (which I will) it can quickly become two weeks.
I change the water in props on Tuesdays and Fridays. Yes, I need set days, or else it simply won’t be done. Habits are powerful, people.
The air pump idea is great – they’re pretty cheap and don’t use much power. The problem is that they’re noisy, however silent they claim to be (though putting them on a teatowel can muffle it). They also need a power source, so can limit where you put your propagation station.
If you have an aquarium, stick them in there _ you can get clips that sucker onto the side, or you can float them in slices of pool noodle
I’m a massive fan of using aquatic moss to oxygenate the water – it’s what I use to keep the water my Thai Constellation oxygenated, and I only need to change the water a couple of times a year (though I really should change it more often and add fertiliser. I can’t really just add fertiliser every six weeks without changing the water because it’ll build up to toxic levels).
Try fertiliser in the water
So for many years we were all told not to add fertiliser to propagations because it would only stress the cuttings
Turns out that was a load of crap.
I recently did an experiment where I took ten (I think) cuttings from my Philodendron brasil and propagated them all in different ways. In the beginning it seemed like the one in Superthrive was winning, but currently the one in fertiliser water is WAY ahead.
One of the things about propagating is that it isn’t always easy to see the winner – the plant that roots quickly may take the longest to produce new growth, so it’s not a done deal yet (and since I started this in February they’re all taking their sweet time to root) but it is pretty interesting.
Also, no new roots – they’re all emerging from old aerial roots:
As you can see water is falling waaay behind, and superthrive has produced a little root but from the stem, not the aerial roots. The superthrive one also goes moldy quickly and has a very displeasing gelatinous quality, that I am NOT a fan of.
Fine-tune the lighting
I touched on this before, but the gist is that whilst leaves are likely to benefit from a bit of extra light when you’re trying to propagate, the roots would prefer to stay in darkness.
Now, I don’t cover my propagation jars, but if you’re struggling to root before the cutting rots then it’s something you could try. All you need to do is tape some black paper around the glass.
Outrun rot by chopping larger cuttings
This is something I learned from Harli G and it makes so much sense – cut your cuttings longer. Especially if you have leggy cuttings, which is often why we’re propagating in the first place.
When you take your cutting, take it as close to the next node down as you can, so you have an extra bit of stem. We’re basically expecting a bit of rot, so we’ve got an extra bit of plant as insurance
I’ve marked it out on my Rhapidophora decursiva, and I’d like you all to ignore the fact that there’s two nodes on the cutting, because there’s only tiny internodal spacing so I can’t demonstrate what I mean.
I’ve circled the node I want to root (again, imagine the one further to the left doesn’t exist). I’ve put a dotted line where one might normally cut (though it’s maybe a bit close to the node), and a solid one where I would cut if I were worried about rotting.
Let the cutting callus over
I’ve got an in-depth article coming up on whether letting cuttings callus over is necessary when propagating plant.
My research unearthed that, no, it’s not necessary to let cuttings callus over before propagating HOWEVER if you’re struggling, it’s worth a go, especially considering how easy (and free!) it is.
After you’ve taken your cutting just leave it for a few hours (or overnight, it doesn’t seem to matter) so the wound can heal a bit, then continue propagating as normal.
Try an alternative to propagating plants in water
Some plants simply won’t propagate in water for me, one of them being Rhaphidophora tetrasperma. If you look at the comments on that post you’ll see that someone cannot BELIEVE that I struggle to root these because they’re SOOOO easy.
I tried in moss, and that worked well. Tip layering also worked, which is like air layering but rather than wrapping the node in moss you stick it back in the soil.
Propagation is something you’ll get better at with experience. It’s a bit like baking bread – it’s great to do your research and collect as much info as you like, but the final result ultimately depends on finding the right environment and setup that works for you.
Also, don’t give up. If you’re sick of mutilating your plants fruitlessly, try air layering.
You root the plant whilst it’s still attached to the mother plant, so it’s faster (because the plant can draw energy from the main root system to grow a secondary one) and if for some reason it doesn’t work and the plant doesn’t root, you won’t lose the original cutting.