Are you finding the leaves on your philodendron plant suddenly curling? It is a common occurrence that is related to one of its growing conditions being on the extreme side of things. That can be the watering, humidity, temperature, or getting the type (or amount) of fertilizer wrong!
While philodendrons are relatively easy to care for (and nurse back to health when something goes wrong), it is preferable to have them grow under ideal conditions, rather than too much or too little of anything, including the amount of light it gets.
All of the ideal conditions are listed below. Look them over carefully because if any of the growing conditions for philodendron plants are too high or low, it will result in the philodendron leaves curling.
Why Do Philodendron Leaves Curl?
The leaves on philodendron plants have hundreds of stomata. These are like pores on the plant leaves. Pores that are constantly opening and closing.
It is one of the fascinating aspects of keeping philodendron plants indoors. They use the stomata to self-regulate their temperature, and they transpire throughout the night, making this an incredible indoor plant for air purification.
What you see as the leaves curling on philodendron plants is this plant’s response to stress. Under duress, the curling reduces the total leaf surface resulting in less moisture being lost through transpiration. Quite incredible!
The key to getting your philodendron back to its gorgeous broad flat leaves is to identify what the plant is getting too much of or not enough of.
How Do You Get Curled Philodendron Leaves Uncurled?
Uncurling the leaves is best left to the plant. All you should do is coax it along with a little TLC. Don’t try to straighten them with your fingers because there is always a reason for the leaves curling. That will be one of the growing necessities listed below being on the low side or far too high.
Identify the cause, correct the conditions.
1 – Start with the Water
Philodendron plants are not greedy. Under the right conditions indoors, they only require a little watering, once weekly. If you’re adding more than that, there is a good chance it has moist soil.
Moist soil is a problem for non-climbing varieties because it compacts the soil and that reduces oxygenation. The roots struggle to cope, and that then shows on the plant when the leaves curl because the roots are failing to deliver the right nutrients. The leaves curl to preserve the little moisture it has left.
Climbing varieties of philodendrons (the type that grows in hanging baskets for its trailing nature) do better with slightly moist soil, but still not damp.
The difference between the varieties of philodendron plants is that climbing varieties have more aerial roots. These varieties can absorb more nutrients directly into the leaves from air humidity. Potted varieties rely on the soil or potting mix for the majority of nutrients.
To check your soil is not compacted, poke your finger into the potting mix. It should be dry to at least one inch. Using your finger, that is roughly from the tip of your index finger to the first joint. Not the knuckle.
If you are unsure, the next best thing is to use a wooden stick. Damp soil sticks to wood. Dry soil doesn’t. If the soil is stuck to the wood further than an inch, it will not need watering. Philodendrons only need watering when the topsoil is dry.
If your soil is too damp, let it dry out before adding more water. The leaves will uncurl as more water reaches the leaves.
2 – Check Your Humidity
Philodendrons are healthiest when humidity is over 50% as they are a tropical plant species. Indoors, this humidity can be reached by frequently misting the leaves on the plant with tepid water.
Alternatively, use a humidifier, or group tropical plants together. If you are growing groups though, be cautious of air flow. Get humidity too high, and there is a risk of biotrophic fungi infection. (more on that to follow).
When humidity is too high or on the lower end of the spectrum, the leaves will curl. To keep your humidity levels constant, try using a pebble tray under the pot, or a humidifier placed nearby.
If you only have a few tropical plants, there are mini-humidifiers that can be placed nearby to elevate humidity around the plants rather than the entire room.
3 – Correct the Growing Temperatures
Philodendrons require temperatures consistently above 55oF, even at night. The preferred range is between 60oF and 80oF. When the temperature drops to below 50oF, the plant will struggle to survive. Over 80oF and the leaves are more likely to curl to preserve water.
The hotter the temperature, the faster the plant loses moisture through transpiration. It curls the leaves to slow transpiration.
Also, consider where your plant is placed because even with the room temperatures being ideal, if it is close to a radiator, the leaf temperature will be higher. Close to a drafty door, the leaf temperature is likely to sway between hot and cold, leading to temperature stress.
The same will happen when these plants are placed near drafty windows. Growing temperatures should always be stable.
Whilst all of the growing conditions favor consistency, temperature is the one growing requirement that must be consistent. The rest are preferable. Temperature consistency is a necessity.
4 – Consider How Much Fertilizer Is in the Potting Mix
Over fertilizing any plant always results in leaf burn, which is seen with browning of the leaf tips. With philodendrons, that happens too, but the leaf curling will also happen because of the excess salt accumulation around the root system. That prevents moisture being absorbed by the roots, stressing the plant to the point that the leaves begin to curl.
Err on the side of caution when feeding philodendrons fertilizer as they do not need much. A balanced (20-20-20) liquid fertilizer will do them fine with just a once monthly spray-on feed in spring and summer.
Always cut back on fertilizer in the winter. When philodendrons aren’t actively growing from fall through to the following spring, cutting back to fertilizing once bi-monthly is sufficient.
If you have over fertilized your philodendron to the point of leaf curl, the solution to uncurl the leaves is to rectify the soil. Treat the plant the same as you would for fertilizer burn because both issues necessitate nutrients being removed from the soil.
The tell-tale sign of over fertilizing philodendrons is brown tips on leaves that curl downward, or downward curling of leaves along with brown spots.
Flush the soil, or replace it with a fresh potting mix. Excessive amounts of fertilizer in the soil will cause compaction, resulting in less oxygenation and less moisture reaching the leaves.
Root damage will occur if the roots are left in soil with a high pH. Damaged roots can lead to root rot, and although doable, fixing root rot is a lot more of an involved process than correcting a growing condition.
5 – Excessive Exposure to Direct Sunlight
Prolonged exposure to direct sunlight will increase the temperature of the leaf surface. The room may feel on the cooler side, but when the leaf temperature exceeds 80oF (which commonly happens when plants are exposed to unfiltered sunlight), the leaves will curl.
Direct sunlight can be a cause of excessive heat that leads to philodendron leaves curling.
6 – Plant Pests May Be Causing Dehydration
Philodendrons, like numerous house plants have sap in the leaves. This is sought by a number of sap-sucking insects. Numerous of these pests are tiny, and all have mouthparts that can penetrate plant tissue making it possible for them to feed on the sap within plant leaves.
Some of the most common sap-sucking indoor pests include:
- Scale insects
- Mealy bugs
- Spider mites
In areas with the temperatures to sustain philodendrons outdoors, there are even more sap-sucking pests to be aware of. These include:
- Stink or Shield bugs
- Squash bugs
- Tarnished Plant bugs
All of these insects have mouthparts that can pierce the leaves on plants, then suck the sap from within. To get rid of any bugs on indoor plants, Neem Oil works like a charm.
For philodendrons kept outdoors, or have insect trouble after a short period outdoors, a blast of water with the garden hose should be enough to dislodge the insects from the leaves. Coating the leaves with an insecticidal solution like castile soap is a preventative measure.
7 – Nutrient Deficiency
Although rare, a nutrient deficiency can cause philodendron leaves to curl. The direction of leaf curling can indicate what nutrient is lacking.
Too little magnesium can cause the leaves to curl downwards, while a lack of phosphorous can cause philodendron leaves to curl upward. To keep the leaves flat, like they should be, stick with a balanced fertilizer as that keeps all the essential nutrients equal.
8 – Transplant Shock
Philodendrons can grow fast, and fast-growing plants usually need repotting every two to three years. When any plant is repotted, there is often a period of stress, and stress is what leads to leaves curling.
If you have recently repotted your philodendron, or replaced the soil mix, transplant shock is a likely cause of leaf curling.
Transplant shock is natural and it only lasts for three to five days. It is just a period of unrest while the plant gets settled in its new potting mix, bigger pot, or a new location.
Changes to its growing conditions can be the only reason for philodendron leaves curling. The leaves uncurl after a short acclimation period.
9 – The Wrong Size of Pot for the Size of the Plant
Philodendrons are vigorous growers requiring a bigger pot every couple of years. Each time you repot these, it is best to choose a plant pot/container that is up to 3-inches wider in diameter than its current one to limit the impact of transplant shock. Go too big too fast, philodendrons will struggle with acclimation.
Without repotting philodendrons, they will become root bound. You can tell when this happens by inspecting the drainage hole of the pot. Roots grow out of the pot.
Inside, the roots will be encircling the pot. Spiraling roots struggle to absorb the moisture content from the potting mix. That is what causes the leaf curling. The lack of water reaching the leaves.
Considering these are long-life plants that can live for decades, there will come a point when it becomes impracticable to go up another pot size. At that stage, you can divide, or propagate philodendrons.
If you suspect your philodendrons leaves are curling because it is root bound, see our guide on how to fix root bound plants.
10 – Powdery Mildew
Philodendrons love high humidity, but so too does biotrophic fungi, of which there are a few species that cause powdery mildew.
Biotrophic fungi require living plant tissue to survive. They feed on plants when humidity is too high, usually in the region of 80% relative humidity.
For that reason, it is ideal to keep humidity between 60% and 70%. Below 50% is too low, and over 70% runs the risk of powdery mildew developing.
The fungal disease gets the nickname powdery mildew because of the dandruff-like coating it covers the leaves with. The result of these fungal spores on the leaves is less light reaching the plant tissue.
While the fungi thrives and spreads, coating more of the plant, it blocks more light as it does, exasperating the problem.
The result is a lack of sunlight reaching the plant, causing chlorosis to set in, slow growth, and slow down the rate of photosynthesis. Leaf curling is only the first symptom that philodendrons show when powdery mildew begins. Until treated, the plant will continue to go downhill.
Depending on your growing conditions, all that may be needed to treat powdery mildew is an increase in air circulation. The less airflow there is, the higher the humidity becomes. Close to or over 80% is when philodendrons become susceptible to powdery mildew.
Leaves that have the fungal spores on them can be pruned away, or treated with a fungicide.