Is your Monstera leaves turning black or having back spots, marks, patches, or splotches? We’ve all the possible causes, common ones being diseases, pests, overwatering, water quality, physical and frost damage.
The less likely reason for Monstera black leaves is too much light, underwatering, overfeeding, heat stress, low humidity, and nutritional deficiencies.
What you will learn will apply to all Monstera species, including Monstera deliciosa, Monstera adansonii, siltepecana, standleyana, etc. Also, depending on the cause, the leaves turning black or having black spots can affect old lower leaves or new upper leaves.
Monstera leaves turning black causes and fixes
There are many causes of black leaves or spots on Monstera, including your Monstera adansonii and deliciosa. Common ones include the following:
1. Diseases – leaf spot and root rot
The number one reason why Monstera leaves turn black, including having black spots, is fungal and bacterial leaf spot diseases, rusts, and blights.
Fungal diseases like anthracnose and botrytis will cause spots, splotches, or leaf lesions that turn brown, dark brown, or black. They can also affect stems or petiole.
On the other hand, bacterial leaf spots like those caused by Xanthomonas species and Pseudomonas species, especially Pseudomonas cichorii, will cause water-soaked lesions. These lesions may enlarge and turn dark brown or black. Also, they may have a yellow halo or not.
What about Monstera root rot? It, too, can be a reason for the brown or black spots on Monstera leaves. For instance, root rot caused by Rhizoctonia species and Sclerotium rolfsii (southern blight) may also affect leaves, causing lesions that may turn dark brown to black.
Practice good sanitation (wash hands and disinfect your gardening tools), isolate diseased plants, discard those with bacterial disease (have no cure), and use fungicide for fungal infection.
We use BioAdvanced 701290B Insecticide Fungicide Miticide to control the various pests and fungal infections.
For the case of root rot, the extent of decay will determine if you can salvage your plant or not. If the whole root ball has been affected, you cannot save the plant. If not, you need to repot your plant. Don’t forget to cut any rotten roots with sterilized pruning shears and use a fungicide to prevent reinfection.
2. Pests and Monstera black spots
These pests will cause yellow, brown, or black spots on your Monstera leaves. A heavy infestation may cause deformed leaves, yellowing, wilting, dropping, and so on.
Most of the signs will be specific to the bug present, and they may include honeydew, sooty mold, silvery stippling, webbing, etc.
If you see tiny black spots on Monstera leaves and silvery stippling, you most likely have thrips. The black, varnish-like spots or frass are nothing other than excrements.
If you see any of the above signs, check for the bugs. They may appear as bumps, dots, or spots with varying body shapes and colors. Some may move or leap while others will remain stationary.
Once you verify that the black marks on Monstera leaves are due to pests, it’s time to act. Some of the ways to control these bugs include:
- Neem oil - A good brand of neem oil is Bonide Ready to Use Neem Oil by SMB Company. It will kill the adult, larval and eggs of insects. Also, kills mites and may offer protection against fungal disease, thanks to the 3-in-1 formula.
- Insecticidal soaps - For insecticidal soap, buy Garden Safe Brand Insecticidal Soap Insect Killer. It has potassium salts of fatty acids that will kill aphids, mealybugs, mites, whiteflies, thrips, scale insects, etc., by contact. Use it for soft-bodied insects only.
- Horticultural oils: Bonide (BND212) - All Seasons Horticultural and Dormant Spray Oil, Insecticide is what you need. This brand has 2% mineral oils that protect your plants from insects and mites and offer protection from diseases like powdery mildew, rust, greasy spots, botrytis, etc.
Also, you can take your plant to a sink and hose it for minor cases. This will dislodge the bugs and flush them down the sink drain.
Last but not least, always insect new plants to make sure there are no bugs. Also, check during your routine Monstera leaf cleaning and dusting.
Monstera leaves turning black is not a typical symptom of overwatering. But it may occur, and your plant may have brown, dark brown, or black splotches.
Typical signs are a wet potting mix even after not watering for several days, lower leaves turning yellow, a mushy stem base, leaf edema (wart-like growths), and wilting that doesn’t improve with watering.
More signs are a moldy potting mix, leaves turning yellow, brown spots with a yellow halo, leaves falling, and mushy black or brown roots.
Don’t water your plant. Next, check if the drainage holes are open and maintain optimum conditions (humidity, temperature, and light). They should help the potting mix to dry fast.
You can poke holes into the potting mix to help it dry faster. But please don’t squeeze the soil to get rid of excess water. It will damage roots.
If your potting mix doesn’t drain well, you need switch to an aroid mix (see Etsy.com). Also, check for any signs of root rot.
Afterward, it would be best if you started watering your Monstera when the top 2 to 3 inches of the soil feels dry. Don’t follow a watering schedule. See more on how to water Monstera.
4. Frost and cold drafts
Water may crystalize inside the cells when exposed to frost or cold drafts. This crystallization will cause plant tissue, and your plant will wilt/drop or look limp.
Some leaf discoloration can occur, i.e., your Monstera leaves may turn whitish, yellow, brown, or black. If prolonged, rotting will happen, and leaves may turn mushy.
To support this, the University of California Agriculture and Natural Resources notes this about frost damage in plants “Then the wilted growth will turn brown or black and eventually become crispy. This means these affected parts of the plant have died.”
If you keep your Monstera outdoors, move it indoors when temperatures go below 50 degrees Fahrenheit (10°C). Also, remove any plants on doorways or open windows.
5. Water quality
Water quality is not likely to cause leaves turning or having black spots but is still a rare possible cause, especially fluoride. When high in chlorine, it will cause a burnt-like appearance and not black. If it is high on salts, it will only affect normal water absorption.
The only possible instance is if your water is high in fluoride. It will accumulate on leaf margins resulting in chlorosis, tip, and marginal necrosis (1) that spreads inward.
When necrosis occurs, affected areas on your Monstera leaves may turn brown, dark brown, or even black. Water quality many explain the black tips and margin your plant has.
If water quality is the issue, you need to start using rain or filtered water. The problem will resolve with time. But if chlorine is the only problem, let the water stand overnight in an open container. Most of the chlorine will dissipate.
6. Physical damage
Sometimes, what appears as black patches on Monstera leaves may be a sign of physical damage during handling or shipping. You should guess its physical damage once you rule out the other possible causes.
Less likely causes of Monstera leaves turning black
It is possible that your Monstera leaves turning black or having black spots is due to any of the below reasons. We considered them as less likely because they rarely make leaves black. Instead, they will make them brown, dark brown, or yellow. Nevertheless, let us mention them.
- Underwatering: Underwatering will cause leaf curling, leaf scorch (crispy brown tips or edges), wilting or drooping, and stunted growth. Also, the leaves may turn yellow or even drop. As the leaves die, they may turn dark brown, and the soil will be dry.
- Nutritional deficiency: When they lack nutrients, your Monstera leaves turn yellow (chlorosis), including in-between veins. Also, you may see brown or yellow spots, stunted growth, distortion, among other signs. If you see purplish-black color, then it may just be phosphorus deficiency.
- Low humidity: In extremely low humidity, Monstera plant leaves will droop, curl, feel dry, and turn brown, including having crispy brown tips and edges (leaf scorch). Your potting mix will dry fast, and plants will need more water.
- Transplant shock: If you recently transplanted or repotted your Monstera, leaves may get scorched, curl, turn yellow or brown. Also, they may drop, fall, and so on. But they will hardly turn black.
- Overfeeding: Too much fertilizer will cause fertilizer burn, leaf scorch, wilting or drooping, and stunted growth. You will also see fertilizer crusts on the soil.
- Too much light: When exposed to too much light or direct sunlight, your Monstera will have sunburn. Leaves will look washed out or bleached and may have crispy brown tips and edges or patches in-between veins. Other signs are curling and wilting or drooping.
- Heat Stress: Heat stress or very high temperature will cause leaf curling, burn, wilting/drooping, and drop. Also, your plant will grow slowly, have yellow leaves, among other signs. It is improbable to make leaves turn black or have black spots.
- Rootbound: If rootbound, your plants will exhibit signs of an underwatered plant which we have given you.