Many of us take great pride in our house plants, so it’s annoying when they become unhealthy. Or even worse, they die. House plants can be expensive, making it doubly frustrating when things go wrong.
On top of pests and diseases, there are issues we sometimes cause that harm our plants. Root rot is one such issue. It’s mostly preventable with just a few simple techniques.
If you love houseplants and want to keep them as healthy and attractive as possible, learn more about root rot now.
What We’ll Cover:
What is Root Rot in Houseplants, and What Causes It?
As the name says, root rot is exactly that – the roots of the plant rot. If left too long, the rot will spread, eventually killing the plant. Root rot will spread quickly once it starts, so if you suspect it, act fast. It never gets better on its own.
Depending on the plant, the demise can be slow or swift, but either way, catching it early and treating it is key.
Root rot generally starts from either over-watering or from the roots sitting in water for an extended period of time. This can be because the soil isn’t draining properly or you have simply watered too much.
Overwatering is common in winter because we sometimes forget that in cooler weather, plants don’t need as much water because some are semi-dormant, and water doesn’t evaporate as readily in humid winter environments. The lower amount of light also reduces evaporation.
Overwatering essentially drowns the roots and makes the plant unable to absorb and move water and nutrients around.
The other cause of root rot is fungi or bacteria. These causes can be in isolation, but often infest a plant due to overwatering. Many pathogens require high moisture to survive and reproduce, and overwatered plants are stressed, leaving them open to problems.
Pathogens That Cause Root Rot in Houseplants
There are two main types of pathogens that contribute to root rot.
Fusarium is a common fungus in the soil of houseplants. There are multiple species of Fusarium, but they all lie dormant in the soil until the conditions are favorable. Usually, this means an overly wet medium and moderate temperatures.
Fusarium favors a cut or wound to enter the plant, but often, the wound is caused by dying roots due to over-watering.
Pythium is a bacterial pathogen that can cause root rot in houseplants. It eats decaying matter, so if your plant’s roots are dying due to overwatering, this opportunistic bacteria will move in.
Pythium can be spread by the fungus gnat, a common houseplant pest. They will spread the bacteria with their feet as they move from plant to plant. The bacteria may sit in the soil until the moisture content is too high or the roots begin to rot.
Signs of Root Rot in Houseplants
Unfortunately, the initial signs of root rot are similar to many other plant conditions, so you must examine the roots to determine if root rot is present.
Be on the lookout for root rot if the plant begins to wilt and the foliage turns yellow or brown. The leaves might develop brown spots or tips, and brown areas might be soft rather than dry and crispy. Stunted or halted growth is also common.
Although wilting, browning, and yellowing are the first signs of many issues that cause a plant to become stressed, pay attention to how the plant shows the signs.
A plant with root rot will often begin to show signs of stress in the lower foliage. Once those leaves or foliage turn yellow and fall off, the symptoms move their way up the plant. This may happen slowly, depending on the overall health of the plant and the severity of the rot.
In order to determine if your plant has root rot, visually examine the root system.
Remove the plant from its container, and gently remove the soil from the root ball. If it’s a larger plant, you may need help, so enlist a friend.
Healthy roots should be white, tan, or cream with a firm texture on most species. Some may be dark brown or even black, but the firm texture is key. No matter the color, they shouldn’t feel slimy, soft, or smooshy at all.
Roots with root rot will be:
- Dark in color, especially if other roots of the same plant are white or cream
- Soft or mushy
- Drop off or fall apart
- Have a terrible decaying smell
Treating Root Rot in Houseplants
If you suspect root rot is the issue, it’s best to start the treatment as soon as you can. Be warned, though: If the disease is too far advanced, you will lose the plant.
Move the infected plant well away from any other plants to avoid spreading any pathogens that may be present. Lay down newspaper or another material that you can dispose of after you have treated the plant.
Make sure you have sterilized equipment to cut away the dead roots. A pair of sharp scissors or secateurs works well. Wipe them well with hot, soapy water, isopropyl alcohol, or a 10% bleach solution.
Gently remove the plant from the container over the newspaper or material. Brush away any growing medium that is surrounding the root ball. If the soil is dry, it should fall off easily.
If the soil is wet, it may fall off in clumps and take some of the infected roots with it, or you will need to remove it manually. Wash the soil away with a gentle stream of water.
Now that you can see what you’re working with, trim away the rotting roots. Avoid damaging or accidentally cutting any remaining healthy roots, but you will need to prune about an inch into the healthy root to ensure you cut away all the dead material.
Re-sterilize your tools and use them to cut off any dead or heavily symptomatic leaves and stems.
Even if you have caught the root rot early and there isn’t a lot of affected foliage, you still need to remove some leaves. With fewer roots, the plant can’t support as much foliage. As much as it hurts us, we need to remove leaves to give the plant a good chance at survival.
The basic rule is to remove the same ratio of leaves as the removed root system. So, if you remove a third of the roots, remove a third of the foliage. Unfortunately, this may mean trimming quite a bit of foliage or height, but it’s necessary for long-term health.
Throw the soil away, including any left in the container.
If you didn’t wash the roots when you removed the plant, do this now and gently dry them with a paper towel. Then, spray them with copper fungicide.
If you are re-using the same container, wash it well with hot soapy water and sterilize it well with a 10% bleach and water solution. If you’re re-potting in a new pot, head to our guide to learn that process.
Repot the plant with a new, good-quality potting mix. Water lightly, but don’t saturate the soil. We want to give the plant some time to recover. Don’t fertilize the plant while it is recovering, as this will cause stress.
Going forward, reduce the amount of water you’re giving by half, or wait until the leaves just start to wilt. You can also stick a finger in the soil and make sure it’s dry before adding water.
You will also want to soak the soil with copper fungicide every three weeks for a few months to kill any remaining pathogens.
How to Avoid Root Rot in Houseplants
Although treatment, especially if started early in the disease process, can be effective, it’s always best to avoid the problem in the first place. To do this:
Use the Right Medium
Use good quality potting mix, and don’t reuse old potting mix unless it’s been sterilized. Don’t be tempted to use garden soil. This may introduce pathogens, but it will also cause the medium to become compacted, affecting drainage.
Over time, no matter how good, potting mix will become compacted. You should replace your potting soil every five years or so.
Use the Right Container
The container you choose should be able to drain well and be the correct size for the plant. If it’s too small, the roots become crowded and too compact. If the potting mix is a heavy one, add peat moss, pumice, or perlite.
Make sure there are enough holes in the container to drain water away from the soil. You may need to add some.
Once you water, empty the drainage catchment pot after 30 minutes. If the water sits there, it will be soaked back up into the soil.
You should also avoid using a pot that is too large. It sounds counter-intuitive, but a large container contributes to root rot.
Understand Your Plants’ Water Needs
Some plants need more water than others. Some are thirsty, and others only need water once a month, at most.
It’s not just about watering on a schedule, either. You should always check the soil moisture level before watering. The water may evaporate more slowly when the humidity is higher or when the weather is cloudy.
Don’t assume that just because the calendar says it’s time to water, the plant needs moisture. Stick a finger in the soil or use a soil moisture meter like this one from Amazon.
It’s not enough to have a moisture meter, you also need to know what amount of water your plant needs. Some plants should be watered to a 7 on the meter. Some shouldn’t be watered again until the meter registers a 3. Get to know your individual plant.
For example, a mother-in-law’s tongue needs hardly any water, but pepromias like more frequent watering.
Then, water needs may change over the year and the plant’s life. Younger plants usually need more water, and older plants get by with less.
If your plant goes dormant in cooler winter months, it may need hardly any water over this time.
Don’t Over-Fertilize
Overfeeding houseplants can weaken them, and excess fertilizer use can upset the balance of a good potting mix. This can stress a plant out, making it more susceptible to fungi and bacteria.
Again, get to know the specific needs of your plants. Some require fertilizer frequently and some hardly ever.
Keep Plants Healthy
Given that stressed plants are more likely to succumb to root rot or the pathogens that cause it, provide the plant with things it requires to stay healthy. That means providing the right amount of light, heat, and airflow, in addition to water and fertilizer.
