The Shocking TRUTH About Root Rot Most People Get Wrong

Symptoms

Let’s talk about the symptoms of root rot first, to which there are many, to help you identify when you might have a problem. The roots of a plant are its foundations, and without a base to grow from, it will crumble into a heap.

Healthy roots equal a healthy plant. The classic first sign is a general and gradual yellowing of the plant. This is normally accompanied by a general unexpected decline with some drooping of the leaves and stems.

• Yellowing Leaves: Roots failing to draw up nutrients.
• Browning Tips: Too much water in the leaf cells causing them to burst.
• Mushy Leaves and Stems: Excess water rotting them from the inside.

I saw this last summer with my Philodendron Birkin. It was suffering from some root rot, and the new leaves were coming out brown and mushy until they died and fell off. Growth abnormalities such as misshapen leaves and stunted growth are also normally evident, so it’s important to act so you don’t have Frankenstein’s plant on your hands.

Causes

So why does all this happen? What is causing the roots of your plant to rot? The conventional wisdom here is that water is the killer. Give your plant too much water, and the roots will start to rot. But this is only half the story.

If this were the case, then plants wouldn’t be able to live in water like so many of them do.

Not enough information is out there regarding this issue, and the general advice always seems to be “Don’t give the plant too much water.” That advice is kind of lazy, honestly. Water isn’t the killer here. The lack of oxygen is.

Or at least it’s one of the two reasons. I’ll come back to the second reason shortly, and it’s one that might shock you.

If a plant’s roots are not getting enough oxygen, they will suffocate in much the same way we would suffocate without oxygen. This should be your primary concern when caring for your plant. Are the roots getting enough oxygen and not necessarily is the plant getting too much water?

Now don’t get me wrong, too much water is a major problem, but it only compounds the issue and speeds up the rotting process, so we do have to get the watering right too. Put your plant in a potting media that has enough oxygen, and you’ll struggle to kill your plant unless you really go for it. This is why I always bang on about not potting up your plant in just soil or compost.

Soil and compost are generally very dense with very few air pockets that suffocate the roots. Add water to this, and you’ve got an accident waiting to happen. You’re adding moisture to a pre-existing problem, generally making things worse.

One of the worst things you can do as an indoor gardener is to dig up some soil from your garden and use it for your tropical houseplants. This is especially true if you have clay-like soil. It’s just far too dense and will suffocate the roots.

I know it’s essentially free soil, but it won’t be free if you end up losing your plant. This is why perlite is plant gold in the houseplant community. Perlite is a lightweight granular volcanic rock that looks and feels like polystyrene.

It’s added to plant soil as a means to increase oxygen for the roots. Perlite is used as a soil amendment because it has high permeability and low water retention, helping to prevent soil compaction. I always add perlite to all my soil mixes, and my plants love it.

I’ve drastically reduced root rot issues in my houseplants since I started using it. My general mix is about five parts soil to two parts perlite, and for succulents, I increase this to four parts perlite to really give my succulents a nice airy mix. The soil of your plant won’t become a bog because perlite is effectively acting as a drain and keeping the soil moist but not wet, as well as providing valuable oxygen around the roots.

Fungus

Let’s talk about the second main cause of root rot in houseplants, and this might actually shock you. Fungus! Yes, fungus is the second reason your plant is rotting and is usually much more damaging than a lack of oxygen. You see, fungus may be present in the soil of your plant but remain dormant for a long time until the soil becomes waterlogged, and the spores come to life and attack the roots, causing them to rot and die.

When I first realized this, it kind of blew my mind. I had no idea this was a fungal issue. For the longest time, I just thought it was a watering issue.

The reason this is usually so much more damaging for your plant is because once a problem starts, it can quickly spread to healthy roots even if the soggy conditions have been rectified, and this can result in plant death. There are three main types of fungus likely to attack the roots:

• Pythium
• Phytophthora
• Rhizoctonia

Like I said, they can remain dormant in the soil and only come alive when the soil becomes waterlogged. So keep your plant in a well-draining mix and water only when needed.

And unless you really know what you’re doing, keep your plant in a plastic nursery pot with drainage holes inside a decorative pot. This will allow the excess water to freely drain through the plant and out of the bottom, which you can then easily discard. You never want your plant sitting in standing water for long, and by long, I mean a couple of days.

Something else you should consider is only watering when the plant needs it, and this means checking to see if the soil is actually dry before giving it water. If you don’t do this, then the soil is at risk of being constantly saturated, leading to a lack of oxygen for the roots and for water spores to become activated. For this, I always recommend the trusty moisture meter.

Watering Tolerance

Every plant’s tolerance to overwatering is different, and this is key. Some plants like to have consistently moist soil, whereas others really need the soil to dry out thoroughly. The obvious examples of this are cacti and succulents that store water in their thick leaves, so they aren’t relying on water in the soil as much.

Saturate the soil often, and they will start to suffer with the leaves rotting from the inside. On the other hand, Calatheas tend to prefer moist soil to prevent their leaves from going brown, which is one of my personal bugbears. If you’re unsure of your plant’s tolerance, then I would always do a little bit of research using Google or even ChatGPT—it really pays off.

So you’re sitting there now, reading this article, and the alarm bells are going off in your head. Maybe you’ve got a plant that is showing the classic symptoms I went through earlier, and you’ve been watering every couple of days, oblivious to the dangers. How should you treat suspected root rot? As in most things in life, prevention is always better than the cure, but I know that doesn’t really help you when you’ve got a plant at death’s door in your hands.

You need to take the plant out of its pot, remove the soil, and closely inspect the roots. You’re looking for any roots that are black or turning black and mushy. Healthy roots should be off-white and plump.

If they’re black and mushy, then cut them out. It can be quite aggressive as well. You don’t want anything suspect remaining because you risk this spreading to healthy roots.

It’s a little-known fact that plants actually benefit from being root-pruned, so make sure you cut everything out that is rotting. Once you’ve done that, repot into fresh soil that’s been amended with perlite and watch your watering. Your plant should bounce back.

Plant World Hydroponics

Transferring plants from soil to water can be a great alternative to soil for healthy roots. How? Because water is made of one part oxygen and two parts hydrogen, making it perfect for plants, and this has a name in the plant world: hydroponics. This is why I remove all the soil from the plant before transferring to water.

You can’t mix the two; this kills the oxygen and rots the roots. Of course, I know what you’re going to say: Water that is left to go stagnant loses oxygen over time and will eventually kill the plant. This isn’t necessarily true.

Stagnant water does indeed undergo less internal mixing, meaning there is less dissolved oxygen for the plant’s roots, but the remedy here is to change the water every week or at least every couple of weeks. I carefully tip the existing water out and then run fresh water over the top for a couple of minutes to freshen everything up.