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You work so hard to keep your plant collection happy. You’ve spent countless hours researching the perfect fertilizer, tweaked your lighting setup to be just so, and spent way more money on IKEA plant cabinets then you’d like to admit. And then you see it; all that effort, time, and care has led to so-so plants and a soil line full of white, fuzzy mold. You have our deepest sympathies.

But before you start chucking your collection into the compost heap, let’s talk about the ways mold ends up in houseplant soil and what you can do to stop it from showing up ever again. We’re going to break down 11 simple tweaks you can make today that ensure your potted plants stay mold-free for good. The best part is, though these take just a smidge more effort in the moment, they will pay mold-free dividends for the long haul.

Okay, let’s start with the easiest thing to check that can help prevent mold: Make sure you’re only watering as much as the plant needs on a given day. You might think you’re setting it up for success by giving it enough water to create a little moisture backup system, but all it’s really doing is creating the perfect breeding ground for mold. That’s the best case scenario, too; the worst case is all of that extra water is drowning the roots and ringing the dinner bell for pathogens that create root rot.

So, how do you know how much water to give your plant? Set the pot on a plant saucer and pour water directly into the soil, avoiding the foliage as much as you can. Once water begins to run out of the pot’s drainage holes and into the saucer, you’re done and your plant is officially hydrated. Remove the extra water in the saucer so that your plant’s soil has the chance to dry out between waterings. 

Potting up, or putting your plant in a bigger pot, is another one of those well-intentioned moves that ends up doing more harm than good. Your houseplant’s roots need time to stretch out and grow, so a pot that’s too big is like moving from a studio to a penthouse suite in a day; what are you going to do with all of that space and how can you possibly fill it up with stuff? Your plant is feeling the exact same way, except it’s sharing its space with way more soil than it needs. We have a tendency to want to water the soil until it looks visibly saturated, and when there’s more soil, there’s more moisture that needs to get used up or evaporate. If it’s just too much for the plant to handle, the soil stays moist and become a perfect breeding ground for mold to form.

So, how big should a new pot be? Shoot for around 2 inches wider than its last house. This size is typically a good compromise, in which the roots have space to grow, but aren’t overwhelmed with too much new soil. However, we’d be bad plant parents if we didn’t point out there’s a bit of nuance to this. A 2012 study in Functional Plant Biology analyzed 65 studies and found that doubling a pot’s size resulted in a 43% increase in the plant’s biomass production. But, these studies most likely also had finely-tuned strategies for controlling the moisture levels in the soil and were probably routinely monitored, so keep that in mind.

No one likes to walk around in soaking wet shoes, and your plant’s roots are the same. When excess water sits on the bottom of a pot, it can’t evaporate and just continues soaking the bottom layers of soil. These layers of soil, coincidentally, are the ones that have the littlest access to oxygen or light, so they end up becoming the perfect incubator for the fungi that create mold, root rot, and headaches all around.

How many drainage holes should your plant pot have? As many as it needs. We know that might be a frustrating answer, but it’s dependent on your plant’s water requirements, the pot’s size, what it’s made out of, and so on. If you’re suspicious that your pot’s drainage holes aren’t enough, try watering your plant and monitoring the soil’s moisture level for a few days. If it seems like it’s taking forever to dry out, it’s probably in need of a few more drainage holes. You can use a drill bit to add more holes to the bottom, just make sure to remove the plant first. If it’s a decorative pot with no holes and you’re not comfortable drilling into it, add a plastic pot with drainage holes that’s wide enough to hit the pot’s rims, but short enough to leave a gap at the bottom. This is what’s known as the “double pot” method and it creates a reservoir where excess water can drain, preventing the soil from staying consistently soggy. Don’t forget to dump it, though, so that you don’t end up with a never-ending pool of stagnant water. 

Plastic pots are great because they’re cheap and come in a variety of styles, but clay or terra cotta pots have a big advantage over plastic in that they can pull moisture out and let air in. This is because they’re porous. That combination of wicking magic and increased air flow can help prevent the soggy soil conditions molds need to thrive. Plus, they’re super easy to customize with paint, embellishments, and can even be given an antique aesthetic style upgrade for those who love the look.  

But, terra cotta plant pots can still grow mold if you’re not careful and not every plant can thrive in terra cotta, so don’t treat them like a foolproof system. You’ll still need to monitor your watering routine and keep an eye out for soil that’s staying moist for too long. You’ll also need to keep tabs on their temperatures and position them away from cold spaces to prevent them from cracking. 

Mold thrives in conditions that let it be lazy, like stagnant air and consistently moist soil. When the air around your plants has trouble moving, whether due to crowding your plants too closely together or just living in a room with a bad HVAC system, it creates an environment where diseases, fungi, and mold can grow and spread. So, make it difficult for mold to grow by keeping the airflow moving around your plants.

There are a few ways to tackle this and it depends on your setup. If your plants are out in the open, space them out so that air can move between the plants. A little overlap here and there is fine, but you may need to break out the pruning shears if the neighborhood foliage get a little too dense. You can also pop on a desktop fan once in a while to help move the air on days when it’s feeling a little too stuffy in the room. 

If your plants are in a display cabinet or enclosed space, buy a few PC fans and keep them running in your cabinet 24/7. We love using these Shutao 5V 60mm USB Brushless Cooling Fans because they’re small, quiet, and hang easily from magnetic hooks and twist ties. Just thread the twist tie through one of the corners to create a loop and hang it from the top inside of the cabinet.  

While there are definitely indoor plants that don’t need much sun to survive, most houseplants you’ll encounter come from tropical regions. Consequently, they expect a certain amount of light and won’t do well if it’s too dark. But what will do well is mold, because it loves dark, damp conditions. If there’s not enough light hitting the soil to help evaporate excess moisture, it makes it harder for the soil to dry out enough to prevent mold from growing. 

Generally speaking, you’ll want to keep your plants somewhere that gets bright, indirect light. We know that can feel a little vague, so shoot for putting them somewhere close to east- or west-facing windows. If you only have south-facing windows or your west-facing window is pretty big, you’ll need to throw something on it to diffuse the light; too much light is just as bad as too little, just for different reasons (such as scorching, wilting, and even stunted growth). Use a semi-transparent curtain, Roman shades, or blinds, and remember to double-check the care requirements for your plants to ensure they can thrive in the lighting conditions of your home. 

Since most houseplants are tropical plants, they love them some high humidity. But, as with all things, too much in excess leads to problems and mold can be the result of too much humidity. It’s just like when there’s too much moisture in the soil and all it takes is a few hours of too-high humidity for mold to start to form. 

Plant species each have their own humidity requirements but, generally speaking, a humidity level of 40% to 60% is ideal for most houseplants. Though, tropical plants enjoy humidity levels upwards of 80%, but those are best left for cabinets — seriously, do not let your home get that humid, because it’s detrimental to your health and can cause heat stroke. You can monitor humidity levels with a smart thermostat or a hygrometer, like this ThermoPro TP50 Hygrometer and Thermometer. Don’t skip this part, though; hygrometers are pretty cheap and well-worth the $15 to ensure your plants have the right conditions they need to thrive, rather than simply become a breeding ground for mold.

Want a method that’s a surefire win against mold in soil? Sprinkle the soil line with a little cinnamon. Not only does it smell great, but cinnamon is a natural fungicide thanks to the compound cinnamaldehyde, so it inhibits fungi growth in soils. 

Cinnamon isn’t just a trick dubious TikTok accounts recommend; it’s promoted as a natural, eco-friendly pesticide for commercial crop production. You don’t need to coat the soil with an entire bottle of cinnamon powder, either. If you’re just using it as a preventative measure, you can sprinkle it directly onto the top layer of soil. If you’ve already got a mold outbreak, mix 1 teaspoon of ground cinnamon in 5 liters of distilled water and let it sit for a few hours. Then, pour it into a spray bottle and spritz the solution directly onto the mold. Its bioactive compounds will begin to work almost immediately to kill off the fungi and mold spores. 

If you’ve got a mold outbreak that you want to prevent from spreading, you’ve got a couple of options. You can opt for just scraping the mold off and see if that’s good enough, or using the cinnamon spray recipe above. But if the outbreak is serious, to the point that all you see is mold or it keeps coming back, then it’s time to repot the plant in fresh soil and dump the old stuff in the trash. For this, you’ll need to remove the plant from the pot and discard of as much old soil from the roots and crown as you can — this will ensure as few stowaways hitch a ride as possible — then put it in a new pot with new soil.

You can opt for a soil blend that’s right out of a bag from your local big box store, but we like to DIY a soil mix that’s designed for popular houseplants, so that we can ensure it’s got all the goodies the plant needs. Whichever method you choose, make sure the soil has stuff in it that allows airflow to move through the soil. Dense, compact soil not only traps water, bringing your mold problem back from the dead, but also makes it hard for your plant’s roots to get the oxygen they need to respirate. 

There are lots of additives that run the gamut in terms of budget and effort. Premade mixes will typically have perlite, which are those little white beads that help break up the soil (you might need a little more than comes standard, especially if you’re heavy handed with your watering can). Other options include vermiculite, bark, LECA balls, pumice, lava rock, coco coir, and more. The point is, your soil is going to need a little help to keep it from compacting under the weight of water, and you can add as much stuff to it as you like. Some people even skip the soil altogether and opt for semi-hydroponic setups or soilless potting mixes.

Watering your plant from the bottom, instead of the traditional top-down method, has serious benefits. Since you’re watering the bottom of the plant, there’s little chance of water reaching the soil’s surface where mold likes to grow. Plus, it gets water closer to the roots, hydrates the entire soil mass instead of just the top inches, and reduces the likelihood of fungus gnats that like to lay their eggs on the top soil.

You’ll still need to be diligent with your watering, though, and shouldn’t leave a reservoir of excess water under the pot — then you’re just back to square one. You’ll know you’ve used enough water when the surface soil starts to look dark, which means the soil mass is thoroughly moistened. Then, discard whatever’s left in the saucer or reservoir and wait for the soil to dry before soaking it again. 

Last, but certainly not least, is checking your house for mold. Mold on houseplant soil is typically caused by microorganisms already in the soil, so it’s unlikely that your plant is picking up spores from another source. However, it’s something to consider, particularly if your home is consistently super humid or you seem to have a chronic mold outbreak on your houseplants even when you’re diligent about your watering and maintaining proper airflow.

The mold that naturally occurs in soil is a saprophytic fungus and is the well-known fuzzy, white-looking mold. Another type of mold, aspergillus fumigatus, is the one that can grow in potting soil if it’s already around your home. It’s just another damp surface for it to live and spread on, and can cause numerous health problems for immunocompromised humans and pets, so providing a breeding ground for it and saprophytic fungi is like a one-two punch of problems. If you see a greenish mold growing on a surface, including your potting soil, you’ve got an A. fumigatus colony growing and need to remediate it as quickly as possible, especially if a loved one has weakened immune systems, asthma, or allergies. Decontaminating surfaces with chemical fungicides can be effective, but you need to call a mold removal company to do a thorough check of your home if it’s really bad.