Yellowing leaves are a plant’s way of telling you something is wrong. It is frustrating because the cause of yellowing leaves can either be easy to identify and treat or extremely difficult because of many possible causes.
The reasons your Philodendron leaves are turning yellow range from watering to root issues, nutrient issues to pest infestations, or the plant’s natural process of dropping old leaves to make room for new ones.
Yellowing leaves can refer to the entire leaf going yellow or random spots of brown and yellow on the leaves. Yellowing can also occur on the edges of the leaf that, eventually turn crispy.
Examining your plant completely is the best way to identify what may be wrong.
1. Temperature Issues
Low-Temperature Stress Identification
Philodendrons are tropical plants not naturally prepared to handle cold temperatures. Most tropical plants can handle low temperatures over short periods. Still, if their environment constantly stays below 14℃, you will see the leaves yellowing within a month or two.
Typically, the older leaves on the plant will start yellowing first, as your plant will kill off one leaf at a time in an attempt to conserve energy in order to survive through cold periods.
Unfortunately (or fortunately), Philodendrons don’t go dormant during winter like Alocasias do. This means that if temperatures are too cold and you do not attempt to give your plant warmer conditions, it will lose all its leaves and die.
In my experience, most Philodendrons are not dramatic plants when it comes to temperature conditions. They will give you sufficient warning to let you know it’s time to put a heater on.
If you’re feeling cold, then it’s very likely that your plant is cold too! If you live in an area where winter temperatures average below 18℃, I would consider taking the following precautionary steps.
- Move your plants away from any windows and drafts.
- Find the sunniest and warmest room in your house and move your plants there.
- If you can, keep the door and all windows closed in that room during the day to keep the heat in.
The sun alone may not be enough to keep your space warm, so you may have to consider heating it artificially. Smaller rooms are easier to manage when controlling heat and humidity.
If you’re adding a heater into your plant room, be careful that it does not directly blow heat onto the plant as it will severely damage the plant. I learned this the hard way, twice.
High-Temperature Stress Identification
It’s not often that Philodendrons suffer damage from natural heat. As long as your plant is out of direct sunlight and in a well-ventilated room, it will be just fine, even during hot summer days.
If your plant has been exposed for prolonged periods to direct sunlight or artificial heating sources, irreversible damage usually will occur within an hour or two. This direct exposure usually turns your leaf a pale yellow or white color, which then quickly dries up and turns black.
If you suspect the plant has heat stress, check if it is near a radiator or is getting a harsh afternoon sun. Plants much prefer stable environments and will not do well with fluctuating temperatures. Consider adding a fan to your plant room to increase ventilation.
2. Watering Issues
This is the most common cause of yellowing leaves.
Philodendrons don’t like to dry out too much but don’t like sitting in waterlogged soil. Over-watering and under-watering problems will present in a similar way – leaves will begin to droop, develop brown spots, and start to yellow. If this is accompanied by soggy, wet soil that may even have an unpleasant odor, this is a sign of overwatering and root rot.
Treatment of overwatering can be as easy as adjusting your watering schedule or as complicated as having to repot your entire plant and remove any of the damaged roots. Overwatering can be caused by watering too frequently or because the plant is in water-retentive soil.
Use well-draining soil like our Aroid soil mix recipes. Always check the soil with your finger before watering, and make sure all excess water drains off the plant.
If you notice your Philodendron has curling, drooping leaves accompanied by crisping and very dry soil, this is a sign of underwatering. The plant will eventually drop these leaves to conserve energy and water.
This is an easy fix – check your soil, and if the top 3cm of soil is dry, it’s time to water thoroughly. Water your plant and let the water run out the bottom of the pot for a few minutes to make sure the soil has absorbed enough water.
From now on, you need to adjust your watering schedule to keep it from drying out too much again.
3. Fertilization Issues
Over-fertilization results in nutrient salts building up in the soil, pulling water away from the plant’s roots, and can get your plant burnt.
Over-fertilization can sometimes be seen by small crystals forming on the top of the soil. The oldest leaves begin to turn yellow first, and the edges begin to go brown and crispy. You may also notice that your plant’s growth starts to slow down.
Luckily, treatment is easy. Give the soil a good flush with clean water and avoid fertilizing it again for around 6 weeks. We recommend only fertilizing your Philodendrons every 4-6 weeks with a well-balanced fertilizer during the growing season.
We also recommend using a slow-release fertilizer twice per year, which can be added to the soil when repotting or sprinkled on top.
You will need to adjust your fertilization schedule or the amount of fertilizer you use going forward to prevent it from happening again.
If you notice irregular yellowing, leaf deformities, and no pests present, your plant most likely has a nutrient deficiency.
Plants need nutrients in order to grow new leaves and sustain current growth. If leaves are yellowing from nutrient deficiency, it is most likely either Nitrogen or Potassium deficiency.
You may notice the leaves becoming a lighter green, and the bottom leaves will go completely yellow. You may also notice browning on the edge of your leaves, and the sections near the veins of your leaves will begin to turn yellow.
If you know you haven’t fertilized your plant in a long time, you can assume under-fertilization is the cause of yellowing leaves.
- Feed your plant with a well-balanced fertilizer every 4-6 weeks.
- A soil test kit can be used to determine which nutrients your plant may be missing, but using an all-rounded fertilizer is usually a safe bet if you don’t have a test kit.
- You may also want to repot your plant to give it an extra nutrient boost.
- Pay attention to your fertilizing schedule to avoid over-fertilizing.
4. Pests and Diseases
If your Philodendron leaves are suddenly going yellow and splotchy, this is likely because you have a pest issue.
Pests such as aphids, spider mites, and scale can turn your leaves yellow as they suck the sap from the plant.
Check underneath the leaves and between the nooks and crannies of your plant, as they do like to hide.
- If you see tiny red and white insects with webs, you have spider mites.
- If you see clusters of white and green bugs, you have aphids.
- If you see small brown bumps with a sticky residue around them, you have scale.
We recommend quarantining sick plants while you treat them to avoid spreading pests. Douse your plant thoroughly in an insecticide spray every day for a week. I tend to remove any leaves heavily encased in spider mite webs, as these can take a few attempts to kill properly. For scale, I recommend removing the bugs with a cotton swab dipped in rubbing alcohol.
- How to Get Rid of Spider Mites on Your Calathea
- How to Identify, Treat & Prevent Thrips on Your Monstera
Viral infections can cause yellowing spots on leaves that quickly spread and cause new leaves to become deformed. There may be some mold present on the leaves or soil.
As soon as you notice an infection, quarantine the plant as some viral infections can’t be cured, and you will need to throw your plant away.
Some viruses can be treated with a fungicide, so you will need to identify which virus your plant has. There are many lists with photographs online that can help you best identify what disease your plant has.
Sterilize all pruning tools, and discard the pot before using them on other plants,
5. Root Issues
Root Bound Identification
If you have not repotted your plant in over a year and the leaves are starting to yellow, it may indicate that it is root bound.
Being root-bound means that the plant’s roots take up the majority of the pot, leaving little space for good-quality soil. If you suspect your plant is root bound, you may notice roots protruding out the top or bottom of your pot.
The best way to see if it is root-bound or not is to remove the plant from the pot. If you do not see a mass of roots, you can put your plant back in the same pot.
If the plant is root-bound, it is time to repot it into a larger pot.
I recommend only going up one pot size. If the roots are completely out of control, I’d recommend going up two pot sizes.
Remove the plant from its current pot, shake off any excess soil, and transfer it into a new pot. Gently fill and cover with a new layer of soil.
Repotting Stress Identification
Most Philodendrons will act out when they are repotted. A few of the bottom leaves may turn yellow and fall off, and the plant may begin to droop, but there won’t be any major damage.
Continue your schedule as usual; your plant will be okay. If you are concerned about root rot and have disturbed the root system, you can cut back on watering for a few weeks.
Place the plant back in the same spot it was in to help reduce repotting stress.
None of the above is wrong with my plant. What could the issue be?
It could be the natural process of the old leaves turning yellow and dying, which is nothing to worry about.
Should I remove the yellowing leaves from my Philodendron?
It’s up to you – you can if you want to, but they will eventually fall off themselves. Avoid removing them too early, as that will take nutrients and moisture away from your plant.
Can yellow leaves turn green again?
Once a leaf has been damaged and turned yellow, it cannot become green again.