The demise of any plant is hard to stomach. None more so than when the cause is root rot. This is a disease that will kill your plant.
Spot the signs early enough, you can do a course correction to dry the soil, prune off damaged roots, and repot in a healthy potting mix.
The question of how to save a plant from root rot is not so much about the repotting process.
It is more about restarting the root growth stage in a healthy mix that gives the plants’ rooting system the absolute best chance of recovery.
Read on to discover the early signs of root rot, whether your plant can survive, and if so, how so.
How to save a plant from root rot
Root rot kills plants from the bottom up. Catch it before it reaches the top of the plant, it can be revived. It will need old soil washed off, damaged roots pruned, and repotted in a suitable size of a plant pot, in well-draining soil with a little plant food to help its recovery.
What root rot looks (and smells) like
You probably already know that overwatering causes root rot. But it takes a while for it to take a grip on the soil.
Most potted plants can withstand some amount of neglect. Not weeks, but a few days in waterlogged soil will rarely rot the roots.
There is a difference between the damage caused by overwatering and the damage done by root rot.
Root rot is a disease that sets in when the roots are left sitting in waterlogged soil for too long.
If saturated soil is your only problem, hold back water to let the soil dry out and it will prevent root rot from setting in.
When it takes hold, the roots turn brown or black, depending on how long the soil has been saturated.
Brown roots are rotting, black roots are dead. None are of any use.
The only roots that can be salvaged are those that are white.
How to inspect the root system for root rot
When you suspect root rot, do not pull the plant out of the pot by the stem.
Root rot weakens the root system and causes the base of the stem to turn to mush. It will not have the strength to cope with being yanked. It will more likely snap.
To remove a plant from the pot to inspect its roots, tip the pot on its side, gently tap the container and smoothly slide it out.
Once the roots are exposed, look for discoloration, but use your nose too.
Rotting roots smell rancid. Like a musty and stale smell, much like damp.
The smell can be present in plants with a light infection of root rot. If it has been going on for a while, you may see fungal growth.
A common sign of root rot disease is mushrooms sprouting from the soil. This happens because mushrooms are a fungus. They grow from fungal spores in the soil and need moist soil to grow.
Mushrooms should not be confused with white fungus balls in soil. Different conditions can cause fungal colonies, but it does not always indicate root rot.
Mushrooms are indicative of the soil lacking oxygenation causing fungi to grow.
Also, have a look around the topsoil, the edges, and the bottom of the soil for white, yellow, or brown spots. Those will be fungal spores. They can start at the topsoil and spread to the deepest layer at the base of your plant pot.
By letting the soil dry out, the fungal spores will go dormant when they do not have sufficient moisture to thrive. They can return though, which is why the soil needs to be changed.
How to dry out overwatered soil
Before doing any work on the plants’ roots, let the soil dry. The soil should only be slightly moist or dry before repotting.
If the soil is holding onto too much moisture, the fastest way to dry it is to wrap the root ball in newspaper, tape it on with duct tape, and then place it in a bigger pot with a kitchen towel or toilet paper layered over the newspaper.
The purpose of the newspaper is to absorb moisture while restricting airflow. The kitchen towel or toilet tissue are more porous so will not absorb as much moisture. Use those to catch the excess moisture the newspaper leaches.
Tightly wrap the newspaper around the soil, making sure it is wrapped tight enough to be in direct contact with the soil and the roots.
Tape the newspaper so there is an airtight seal, then wrap layers of toilet tissue or kitchen towel on top of the newspaper. Place it into a big bucket, and leave the paper to soak up the excess moisture overnight.
In the morning, remove all the paper. The soil will be dry enough to inspect the roots, revealing the true extent of the damage.
Cleaning up the salvageable roots
Before stripping the soil away from roots, have your new potting mix and a clean pot ready for repotting first. The longer the roots are exposed, the more likely it is that the plant will go into shock.
The best practice for repotting any plant is to work fast.
Aim to have everything done in under three hours. The best way to accomplish that is by preparing everything in advance of unpotting your plant to repot it.
- Have your potting mix ready
- A clean pot ready
- Sterilizer (such as a spray bottle of hydrogen peroxide)
- A jug or basin of water at room temperature. Do not use cold water.
To prevent the risk of root rot recurring, old soil around the roots should be eliminated. Remove all the soil, or at least as much as you can.
The added benefit is you will have a clearer view of the roots to see which ones stand the best chance of recovering.
To remove most of the soil, use your fingers to gently push away the soil from the root ball. Work gently to avoid damaging the roots.
The soil being removed should be kept clear of your new potting mix to prevent any fungal spores, bacteria, or even pesky houseplant bugs from getting into your new potting mix.
Once you have the majority removed, pour some water over the roots to clean them up.
With all the soil removed, you will can see which roots are discolored (sick) and which ones are healthy (white roots).
Pruning rotted roots
Sterilize your scissors or pruners to cut away damaged parts of the roots.
On partially rotted roots, make the cuts just above where the discoloration ends. Roughly about 1-inch at least just in case there are lingering pathogens, or perhaps insects feeding on the roots causing the damage.
Brown and black roots need to be pruned off the plant. Healthy plant roots will be white, or a slightly yellow shade. Closer to white than yellow. The same as decaying leaves, the roots turn yellow first, then brown, then black.
Slightly yellow roots may survive. There will be a higher risk of a recurrence if there is an early infection of bacterial or fungal disease already established in the root.
If it’s only caused by a lack of oxygenation from prolonged waterlogged soil, yellowing roots can recover.
Leave them on if you have a lot of root damage. If you have enough healthy white roots to work with, only keep the healthy roots, and prune away the rest.
When you are finished pruning, spray a fungicide over the roots to kill off any fungus or bacteria.
Mix 5 ml of hydrogen peroxide (3% solution) with 240 ml of warm water. Use either a spray bottle to mist the roots, or dip them in the diluted solution.
The most appropriate type of container to repot in
To give your plant the best chance of fighting root rot disease, it is imperative to get the pot right. Both in size, and materials.
- Plastic plant pots hold moisture the longest
- Glazed terracotta pots are in the middle range for moisture retention
- Unglazed terracotta pots are more porous; therefore, the soil dries faster in these.
In terms of size, you do not want to go too big. A decent ratio that serves the roots best is to repot the plant in a container that’s 25% bigger than the entire root ball.
Getting the potting mix right
Different plants require different soil mixes.
The best potting soil for houseplants will help some flourish. Others grow better with various ingredients to make an ideal potting soil mixture. These can have amendments added to improve aeration and drainage.
If you have quality compost you can use to enrich the soil, make sure you have the ideal soil to compost ratio. Too much will do more harm than good.
Add plant food to your mix to help roots grow back strong
The stronger the roots your plant develops, the longer it will live.
The best way to prevent a recurrence of root rot disease in a recovering plant is to help the roots get off to a flying start.
Do that by adding some plant food, and supplements to improve aeration and balance out moisture retention with just enough drainage to prevent waterlogging.
When you repot plants, it is rarely wise to include a fertilizer early on. Unless that fertilizer is organic, which prevents root burn.
Some of the best fertilizers for garden plants and some houseplants will include:
- Worm castings
- Alfalfa meal
The NPK balance in each of these is close to neutral. The main benefit they have is being rich in macronutrients.
These improve the structure of soil (such as hydration, aeration, and drainage), as well as attaching to the roots, helping them soak up more nutrients from the soil.
The result of adding granular organic plant food into your potting mix is stronger root growth with a higher ability to fight off diseases.
How to save a plant without roots
If all the roots are rotten, the plant can only be salvaged by propagation.
Some of the easiest houseplants to propagate include pothos plants, sansevieria (snake plants), spider plants, the ZZ plant, and Pilea Peperomioides.
It is easier to learn how to propagate succulents than, for example, how to propagate a peace lily, which is done by division, then planting healthy clumps.
Succulents only need a partial rooting system. However, if all the roots are rotten, you can root from stem cuttings in water or soil.
The peace lily, being an herbaceous plant, cannot be propagated from cuttings, but instead, from divisions.
Regardless of whether you’re struggling with a broadleaf plant, succulent, or a prolific bloomer that seems destined to death, there are some methods you can put into action to rescue a dying plant that has succumb to root rot.
By the very nature of root rot, it starts at the bottom working its way up the plant, rotting the stems from the base up.
If you catch it before the leaves at the top of the plant show signs of decay, there’s likely part of the roots healthy enough to survive.
When all the plant is decaying, there’s probably no healthy roots left to save.
Rescue plants from root rot through propagation
When a plant’s root system is destroyed by root rot, a last-ditch survival attempt is to grow new roots from stem cuttings.
Depending on the size of the plant, it can take months for roots to emerge.
It is possible to propagate stem cuttings in water or soil. Roots develop in water faster, however, if you leave them in water for too long, they can struggle to adapt to the soil later.
To get them off to a good start, you need a cutting from a healthy stem.
On a dying plant, the healthiest will be at the top, or a side shoot near the top.
When taking the cutting, cut the stem slightly below a leaf node. That is the part where the leaf emerges from the stem.
The closer to the base of the stem, the higher a chance it will put out roots instead of a new leaf.
If you are propagating cuttings in water, only let the roots grow to a maximum half-inch in size then transplant in soil.
Otherwise, they can go into shock at which point the roots will struggle to adapt. They will have acclimated to growing in water.
You can also start the process in soil. For the best chance of new roots growing, dip the base of the stem cutting in a rooting hormone powder, then plant it in soil.
Frequently Asked Questions related to saving a plant from root rot
Do the leaves need to be cut off the plant when roots are damaged?
The more foliage the plant has, the more work the roots have to do. When a lot of roots were damaged, defoliating the plant will put less stress on the remaining roots. Proportional pruning is beneficial. For example, if around a third of the roots were lost, remove a third of the plants’ leaves.
How much water should be added to repotted plants recovering from root rot?
When repotting, moisten the soil first to lessen the water it needs. Leave a quarter-inch lip between the soil line and the top of the plant pot. Water only until the water pools on the topsoil. Not until it drains through the drainage hole. Wait until the soil dries almost completely before rewatering.