Discovering nasty lumps of mold on houseplant soil is something most plant lovers dread. It can be a recurring nuisance unless dealt with effectively, too! Even then, the potential for discovering mold exists whilst ever we have live plants in our homes.
In this guide, we will take a look at how to get rid of mold on houseplant soil, and how to deter mold from growing any further. We’ll also help you identify the different types of mold in and on houseplant soil as well as the plants themselves. Want to know how to prevent mold in plant soil for good? Here’s where to start.
How can I tell if there is mold on houseplant soil?
Mold in soil will require a little probing to detect it unless it’s evident on the surface. You might notice a little white powder, or fungus, on the top. However, some of the worst fungi and mold can lurk beneath…
Experienced plant parents often systematically check soil for dampness before watering, for example. That’s a great time to check below the surface to check all is okay!
Houseplants are usually watered regularly (or, they should be!). This may be weekly, fortnightly, or for cacti and other succulents, over extended periods. Prior to watering, even if no mold is visible on the surface, it’s a good idea to gently take a look an inch or two down.
Probing the soil
If you love looking after indoor plants, it’s likely you will have more than one in your collection. As we all want to be part of the solution and not the problem, we must consider how to check out soil properly to ensure that mold isn’t causing issues deeper beneath the surface.
When it comes to everyday mold and fungus, spores are easy to transmit. Within the confines of soil, we can stir them to move to another part of the pot or even roots. If they are already there, the whole pot will need treating – sorry!
What we must be careful of, however, is not spreading the mold on plant soil to other houseplants.
How to stop mold spreading across your houseplants
If you are worried that one houseplant in your collection is likely to start spreading mold to others, here’s what you need to do to take action.
Prepare your space – and your tools
Prepare space to examine your houseplant soil. Choose a well lit area where you can lay out items you will be using to examine, too. These are:
- A piece of newspaper, old magazine or tray you can wash. Have some absorbent tissue or kitchen roll handy – and toilet tissue will work well, too
- A clean, empty plant pot, used and washed ice cream carton or any old vessel you can throw away afterwards
- A probe – a lollipop stick, plastic fork, or even old metal cutlery will work. Make sure to sterilise them between uses if you are going to use them in future
- Damp tissue (again, toilet paper is fine)
Move your affected plant
Move your houseplant away from the close proximity of others. If you have moved some houseplants outdoors in summer, this applies to them, too! If you do this indoors, have a sheet of newspaper or some tissue under the pot, ready to catch any grains of soil or compost.
You may also be lifting off dead leaves from the surface of the growing medium. You may also be removing fungal matter from within the soil! In severe cases, you may have to remove the entire plant! More about that later.
At this stage, remember prior to watering, the soil should be powdery.
Start probing the soil
Slowly and gently, using a lollipop stick or fork, skim across the surface of the compost. Do this slowly and start near the base of the plant. At this point, do not dig into the compost – it’s the strongest point of the plant.
Gradually work your way outwards and in a circular fashion around the plant. As you get nearer to the walls of the pot, you can probe a little deeper. The root system of your plant will usually have roots nearer the surface, close to the centre of the plant. For this reason, we recommend you probe deepest at the edge of the pot.
Depending on the size of the plant and accordingly size of the pot, you may need to lift a little soil or compost out. If it’s clear of mold you can return it to the pot in a few minutes. Lift sound compost if soil into one of the cartons you have to hand.
If you find the soil is clear, simply return your soil sample back into the same house plant pot and move in.
However – be cautious. Do not be tempted to put that soil sample into another plant pot. There is a chance spores are present, but not well enough developed to be seen by the naked eye. You do not want to inadvertently spread the spores from a contaminated pot to a clean one!
What to do If you discover mold in your soil
If you discover mold, you will need to check roots for rot. If you come across discoloured or mushy roots, more intensive action may be needed. Gently lift out your plant and place it on the newspaper. If it’s very wet, use the kitchen roll or toilet tissue to soak up moisture.
If you are going to, perform some surgery, at this stage, you will need a thoroughly clean pot to hand. If you have followed our suggestions, this will already be nearby! If you are reading this alongside the activity, stop here and collect your sterile pot, soil or fresh, healthy compost in which to place your recuperating plant.
Lay your plant on its side and select the worst affected area first. Use tissue to gently scoop off mushy matter. There is no point trying to cut mush off because the moisture will spread on your operating table!
Once most of the mushy parts have been cleared away, select seriously damaged roots and use a clean tool to slice off the damage. Wipe your tool between cuts to minimise the potential for spreading the problem.
Place clean soil or compost in your clean pot which are to hand and settle in your plant.
Do not over water – add only a small amount of water near the base of the plant where the root system is more concentrated.
If you have amputated a large number of roots, your plant may need support. Place it out of draughts and avoid full sun for a few days to allow roots to recover.
Isolating your plant
At this early stage of recuperation, you want to ensure you have cured the problem and that you are not about to spread it to contaminate other plants in your collection. Equally, your plant patient is extra vulnerable at present. If other plants in your collection have problems, you need to protect it from those.
When you see that your plant is holding its own, looks perky and comfortable and not wilting, you may consider returning it to a favourite spot. Ideally, you will have checked other plants in the vicinity.
Take heart – as mold may not be fatal. With care, plants can survive and develop well. The sooner they are treated, however, the less intervention will be needed. Even in the worst cases, most gardeners are optimists and we believe that where there is life there is hope!
How to get rid of mold in houseplant soil
Now, the fun part – getting rid of mold. This is easy to do in a variety of different ways. However, many of us stand by the fact that prevention is better than the cure. We’ll get to that shortly.
Here are some quick and interesting ways you can get rid of mold on plant soil:
- Dry it out in the sun! Ultraviolet light is a powerful enemy of mold. A spell in direct sunshine kills off mold on the surface of soil – it’s true! Placing houseplants on a windowsill in direct sunlight can be a free and effective solution. Mold thrives in moist conditions, so the warmth of the sun will help dry out soil, too.
- Dust damp soil surfaces with bicarbonate of soda, or baking soda. It’s a cheap, quick way to gently suck out water from areas saturated with water.
- You can just pick it out – but be careful with where you dispose of it. Using a clean blade (a plastic picnic knife or even a sliver of cardboard will suffice), skim off mold from the surface of soil and discard carefully in a covered container or folded in paper.
How to prevent mold in houseplant soil
Mold thrives in moist and/or decaying organic material. We have to water our houseplants – of course – but overwatering is a major contributor to the problem. In fact, giving house plants too much water is one of the main ways mold takes up residence in your house plant pots!
How to stop mold in plant pots – four easy solutions
- Do not over water houseplants. Wait until the top two or three inches of soil or compost are completely dry before re-watering.
- Ensure your houseplant pot has adequate drainage. The water should escape easily to drain into a saucer container. Empty residual water in the container quickly. Do not allow your houseplant to sit in it for long.
- When you buy or are gifted a houseplant, check the growth medium and plant for evidence of mold. Ideally do this before taking it inside your home! Examine soil or compost as described above. If in doubt, re pot as described above.
- Only use clean soil and compost.
But… what is ‘clean’ soil or compost?
By clean, we mean – as far as possible – ensure that the growth medium you use is clear of mold. If you buy a new bag of compost or collect some from your own homemade supply, check the even tone and texture. Check if there are any particularly sodden clumps and/or the odd piece of large dead or decaying matter.
For example, this may be in the form of a thick piece of twig or clump of leafy material. Remove those and don’t be tempted to put them in the pot. They could have already been targeted by fungus.
If you should find any mold on plant soil or compost, it may present you with a dilemma. You may wonder whether or not you could make it safe to use elsewhere. Weirdly enough, the answer is ‘maybe’!
How can I make soil safe to use for my houseplants?
You can sterilise it! Yes – strange but true – with a little time and effort, it’s possible to kill off potential problem fungal spores.
To do this effectively, you will need to cook it! Fungi can not survive at high temperatures. You will need to find a heatproof container suitable to place in your oven and a sufficient tin foil or lid to cover it with. An old casserole dish is ideal.
Do make sure you cover the soil in the container before you place it in the oven. You will need to cook this for 30 minutes at a temperature of 180 degrees Fahrenheit or 82 degrees Celsius.
However, take care. Do not cook your soil at a higher temperature, because toxins are produced above those degrees. Otherwise, feel free to give your soil the heat treatment to kill off any moldy nastiness!
How to prevent mold from getting into the soil of houseplants
Mold spores are easily spread when airborne. You can reduce this occurrence by taking some practical steps.
Firstly, keep houseplants away from draughts. Houseplants hate being in draughty spots, so it’s best to keep them away from doors or particularly breezy windows. Draughts whip up spores and carry them to other areas where they deposit them on available surfaces.
Once even a single spore settles on the surface soil of a houseplant, rapid contamination of soil can occur. Mold contamination is easier to prevent than cure – believe us!
If you bring in soil or compost from outside, check it carefully before using it as a growing medium for indoor houseplants.
You should also keep your containers and tools clean. For example, always empty containers and clean them thoroughly before reusing them. You can sterilise them with a homemade solution of nine parts of water to one part of bleach.
Mold spores can collect in dust on your houseplants
It’s true – you may need to give your plants a quick dusting down every now and again!
As we’ve said, mold spores travel in air. You can avoid wafting them onto potted houseplants by not dusting with a dry cloth. This can be easily overlooked when you clean dust off the leaves of houseplants and pots.
Smooth, glossy leaves are particularly susceptible to collecting dust. For example, the leaves of rubber and Swiss cheese plants are sizeable dust magnets! If you dust any of the leaves housing spores, chances are some will fall into the surface of the soil and begin to multiply.
To avoid this, simply use damp tissue or a flannel. You can recycle scraps of fabric for this purpose and simply wash them periodically.
How to tell if mold is active or inactive
Mold can be dormant or active – and identifying which you are looking at is simple.
Dormant mold is like fine, white powder. It causes fewer problems than active mold. Unlike active mold in soil or compost, it does not compete for nutrients.
Active mold, however, is generally more moist – and so easily forms a paste if you press down on it. It is soft and silky to touch, with more tangible texture than dormant mold.
What is the difference between mold and mildew?
Many of us have confused the two and sometimes people believe they are the same. In fact, it’s easy to visually detect the difference if you look closely.
Mildew grows on plants in a flat form. Mold builds to rise off surfaces or within matter, takes on a form of its own. Though suppressed by other surrounding matter, mold tends to be more easily recognisable. So now you know!
What are the most common mold types I might find in houseplants?
There are several types of mold which, as living organisms, feed off organic material. They are known as ‘saprophytic’.
The most common ones you are likely to come across are; Aspergillus, Mucor, Trichoderma and Penicillium. Feeding and thriving, they often spread freely and can be difficult to eradicate.
Mold in houseplant soil may hardly be noticeable for a long time. Even then, it is not always fatal! By following our guide, and with a little extra TLC, your houseplant soil and compost can be mold free in no time at all.