If you’re seeing new leaves on your Monstera turning yellow, there’s something wrong with the growing conditions.
Older leaves on a Monstera plant turning yellow is to be expected. It’s natural and it is a good sign that the plant is channelling its energy where it’s needed. Towards the new growth, which shouldn’t be yellowing prematurely.
3 All-Too-Frequent Reasons for Monstera Turning Yellow
1 – Limited Exposure to Light
Every plant needs light to help it grow and maintain its health. Some more than others. The Monstera is not a huge fan of bright light. It does considerably well in low-light conditions, but it may still need a little extra light exposure.
The leaves on Monstera plants turning yellow can be a sign of inadequate light conditions.
On mature Monstera plants that are over 3 years old, you should be seeing some fenestration happening. This is when the leaves split, giving the foliage its distinct appearance.
Without sufficient lighting, the leaves won’t grow large enough to split and may retain their smaller heart shapes. When yellowing happenings, it’s usually on the veins, or in patches rather than the entire leaf.
East and west facing windows normally (depending on your location) give Monstera sufficient light. North-facing windows get the least hours of sun exposure, and south facing will be too much direct sunlight for a Monstera, risking leaf burn.
If you can, try moving your plant to a window that’s east or west facing. If you’re limited on natural light, you can use artificial light and it doesn’t need to be grow lights. A grow bulb in a standard light fitting can be sufficient, and it’ll be more economical.
If you’re really stuck for natural light, consider fluorescent lighting. A number of kitchen cabinet light units use fluorescent light tubes. Some are LED. Both fluorescent and LED lighting are suited to Monstera because neither give off much heat.
The more heat the plant gets, the faster the soil dries.
2 – Too Much Soil Moisture
A more common cause of Monstera plants yellowing is overwatering and you don’t need to water it too frequently for it to become an issue.
Soil drainage is often the culprit of leaves on indoor plants yellowing. That’s why potting mixes are better suited to house plants than your typical garden soil.
The potting mix for Monstera needs to be well-draining. Peat moss is the most widely used as either half potting soil and half peat moss or coco chips, or a 3/4 mix of potting soil mixed with either a 1/4 of pumice or perlite.
Generally, Monstera plants need to be repotted every two years, because over time, nutrients diminish from the soil, and trace minerals such as calcium from tap water and any excess salts from fertilizers eventually build up and effect the soils ability to drain.
That’s what usually causes overwatering to be an issue. Not actually drowning your plant with gallons of water.
The more compact the soil becomes, the less effective its drainage.
Another thing you can and should be doing is aerating the soil before adding water. Without aeration, the soil in containers is more likely to compact, and restrict air flow to the roots.
When the soil becomes compact, it restricts drainage, resulting in more surface water. Expose any house plant to standing water for too long, and damage will set in.
Yellowing on the leaves is usually among the early signs of overwatering. Knowing how to aerate soil in potted plants naturally using organic matter is a good step in the right direction and works better than poking the soil with a chopstick before watering the plant.
Some materials that help increase soil aeration include shredded bark, sphagnum moss, and coconut fiber. As they breakdown, they create air spaces in the soil, preventing it from becoming compacted.
3 – Too Low a Humidity Level
The other aspect of Monstera plants that can lead to the same signs as overwatering is too low a humidity level.
Monstera are a tropical plant species so what’s comfortable for you, isn’t the same for the plant. They prefer high humidity in the 60% plus range. A difficult feat if you want to co-exist with them in the same room.
There are a few ways to make it work though. The simplest is misting, but there is a hands-off way to increase the local humidity around plants, without increasing the relative humidity of the entire room.
That’s by grouping plants together. Specifically, plants with a high transpiration rate, aka, humidity plants or air plants.
All plants will release some water vapor into the air around them. It’s the natural process. You add water, the roots soak it up, distribute the water throughout the plant, and then on the leaves, there’s tiny pores that allow water to release as a vapor. It’s how plants stay cool.
What each of these plants have in common is they all guttate, which is basically sweating out excess moisture. Only about 5% of a plant’s water intake is released through transpiration.
Tropical plants use a process called “guttation” to sweat out excess moisture and minerals. When you put more of the same types of plants in a small grouping, the microclimate around them can increase the growing humidity due to both water transpiration during the day, and the guttation process that happenings overnight when the lights are out.
If you don’t have the space to grow groups of large-leaf tropical plants, another thing to try is using a humidity tray. Humidifiers are an option – if you don’t mind increasing the relative humidity of the entire room.
Failing that, move your plant to the bathroom/shower room where there’s always going to be higher humidity.
5 Pests That do More than Discolor the Leaves on Monstera
When you’re only seeing patches of yellowing, there’s a chance it’s pests that are feeding on your Monstera. Usually these…
1 – Scaly Insects
Scales can be soft bodied or the armored ones that have a hard shell. Both are hardy and regardless how hard you try, they can find their way onto nearly every type of houseplant. Monstera aren’t an exception.
If scales are present, you’ll see tiny brown bumps littered across the leaves. They can be picked off by hand, or the better option is to use a Q-tip with some rubbing alcohol on it to remove them.
It’s not recommended to rinse them off because it’s likely to result in the scales landing in the soil where they can lay eggs.
Even once scales are removed, the larvae are so small you won’t see it, which is why it’s safer to treat the plant with a neem oil application or an insecticidal soap to kill any larvae left on the leaves.
If scales are left attached to the leaves, they will suck the juice out of the plant, causing it to yellow and stunt growth.
2 – Spider Mites
Spider mites are super hard to spot. At first glance, they just look like a cluster of tiny brown dots speckled about on the underside of your plant’s leaves. Look for long enough though, and you’ll start to see them move.
Spider mites tend to be found on the underside of leaves and they feed on the sap and they excrete honeydew, which is a sticky substance that can coat the leaves to the extent that it prevents light from being absorbed by the leaves, resulting in chlorosis.
Suffice to say, they need to be gone as soon as you see them, and it doesn’t take much. They aren’t resilient to much so neem oil tends to do well at getting rid of spider mites.
3 – Whiteflies and Mealybugs
Whiteflies and mealybugs look similar and behave the same way, which is to suck the juice from plant leaves. The only difference is whiteflies can fly; mealybugs can’t.
If you have whiteflies, they will fly away whenever the plant is disturbed. Move the leaf and see what happens.
If they crawl, rather than fly, that’s probably mealybugs, although only the adult mealybugs are white. Younger mealybugs can be a tan or brown color too.
For treating whiteflies, an insecticidal soap treatment is better because what you need to kill is the larvae and eggs before they emerge with wings. For the flying insects, yellow sticky tape is handy as a trap.
Mealybugs can be treated easier using a Q-tip dipped in rubbing alcohol. Similar to whiteflies though, treat the leaves with an insecticidal soap to get rid of any lingering larvae.
4 – Aphids and Ants
Aphids are common on many houseplants and while the same treatment as most household plant pests can be applied, there’s an extra pest worth mentioning that too often escapes unnoticed. The ant.
Aphids and ants have symbiotic relationships because of how they feed. Aphids feed on the sap of plants, excrete honeydew and ants feed on honeydew.
The two insects work together. Ants farm aphids onto suitable plants, coax them to feed so they can then feast on the honeydew. Insects are smart creatures.
If you’re having an aphid problem, check in and around your home for ant nests too.
5 – Fungus Gnats
Fungus gnats are more annoying than they are damaging, but like most things, give them enough time, and they can do some serious harm. The most damage is done by the larvae laid in the soil. That’s what feeds on the roots of the plant.
There’s good and bad news though. Fungus gnats only set up home where it’s overly moist, so if you have a problem with these, you have a drainage problem. That’s the bigger concern. The fix for that is to repot in well-draining soil.
Treating the soil for fungus gnats can be done by adding a thick layer of Bacillus thuringiensis (BTI) but the bigger problem needing addressing will be the high moisture in the soil that attracted them in the first place.
3 Fungal Diseases that Can be the Cause of Monsteras Turning Yellow
1 – Anthracnose
Anthracnose is a fungal disease, however on infected plants, the leaves will turn a tan brown to black colour. Starting out, it’s dark leaf spots with a yellow halo surrounding darker lesions on the leaf.
On houseplants, this is rarer than most other fungal diseases, unless, you’re using compost from your garden compost bin.
If you put any material in your compost bin that’s infected, there is a chance of it surviving and infecting the plants you use the compost on.
Anthracnose is one of those fungal diseases that’s soilborne. The only way to get rid of it is by cutting away the diseased leaves and repotting in fresh soil.
A more proactive approach to treating anthracnose is a weekly application of liquid copper fungicide. Be wary of too much though as copper is only beneficial in small doses. Too much exposure to copper will further damage the plant.
If you do use a copper fungicide, err on the side of caution and dilute it.
2 – Powdery Mildew
Powdery mildew can be caused by poor air circulation, inadequate light (less heat), over fertilizing, and too high a humidity. Given that an effective way of increasing humidity for tropical plants grown indoors is grouping, you have to be careful not to group too many.
There’s a fine balance to strike between grouping your plants and over-crowding them. That’s usually when humidity levels can get dangerously high that it risks fungal growth.
Powdery mildew won’t damage a Monstera plant if you catch it early. Left long enough though, and it can lead to the leaves yellowing.
Treating it can be done with a fungicidal treatment, many of which are available off-the-shelf, as is a regular application of neem oil or liquid soap.
3 – Root Rot
Root rot is what happens when you don’t use a well-draining potting mix, drown your plant frequently, or don’t occasionally aerate the soil.
If the water can’t drain freely from the soil, the roots of the plant will be sitting in moist soil being starved of oxygen causing them to suffocate. Eventually, the roots turn black, and the plant dies.
Before that happens, wilting and yellowing on the leaves can be a sign that the plant is struggling. Especially if the yellowing becomes darker.
This only sets in when the soil is left with high moisture for a while. Since Monstera plants drink a lot and transpire and guttate, it takes a lot to drown them.
They aren’t infallible though, which is why they should only be watered when the top 2” of soil is dry to the touch.
When you suspect the roots are struggling, remove the plant from the pot to inspect the roots. Rotten roots will be black, feel mushy and have a horrid smell to them.
Some parts of the root system may be salvageable so it’s a good idea to rinse the roots, trim away the dead parts, and the ones that look like they might survive, give them a chance in some fresh soil that is well-draining.
It is possible for a plant to recover provided the entire root system didn’t rot.