Even the most novice of gardeners knows that indoor plant leaves turning yellow is not a good sign. The problem is that yellow leaves is the most common symptom of a wide range of houseplant ailments, and it can take a little experience to know what the root of the problem is.
Sometimes it can be serious, sometimes it’s temporary and sometimes you may have to change up your care routines to fix it.
Here are the common reasons why your plants leaves may be turning yellow, and some easy steps to get them healthy again.
1 – Lack of Sunlight
Getting too little light is one possible cause for yellowing leaves, and the first thing most indoor gardeners think of. While a likely source of concern, it’s just one of many.
Are the leaves closest to the light still green, and only yellowing on the far side? That can be your hint that light is the cause.
Find a sunnier location, or make an effort to turn the plant more often so that the backside is getting enough light. Adding an artificial light source can also solve the problem. It doesn’t need to be a fancy plant light either.
A standard lamp can be enough to green things back up again. If you can, choose a bulb that is “cool” in color tone rather than “warm” (in other words, slightly blue instead of slightly red) to encourage greener leaves.
Sometimes having too much light can also cause yellowing but that usually changes to brown as the leaves dry out. Unless you have a very hot or sunny location, or are growing shade-loving plants, this is a lot less likely than having too little light.
2 – Low in Nutrients
Plants will also start to yellow when they are not getting the right balance of nutrients. It may be a number of elements, but it’s probably a nitrogen shortage.
Nitrogen is necessary for lush green leaves and will be depleted if you haven’t repotted your plants for a while. Is it the newer leaves that are yellow? That’s nitrogen.
On the other hand, are leaves turning yellow in different patterns (yellow along the veins, or just the edges?), then there is another problem with the soil. Yellowing on the edges is probably a lack of potassium, for example.
A little soil test kit (view on Amazon) can let you know what your soil is lacking. Once you pick one up, simply follow the directions. It usually just means taking a sample of your potting mix, adding water and the various reagents in the kit. Compare the color to the chart, and that’s it.
Fixing a nutrient problem is as simple as getting a little fertilizer, as long as you have narrowed down what minerals you are lacking. Fertilizers come in a huge range of nutrient contents and concentrations.
Adding the wrong one can make things worse, which is why you need to do the tests first.
Though not exactly the same as nutrient content, having soil with the wrong pH level can also lead to unhealthy plants and leaves turning yellow. The pH should be roughly neutral (or 7), and it can get too acidic over time, and organic compounds in your potting mix start to break down.
You can get a separate testing kit for this. Just remember that the lower the number, the more acid the soil.
3 – Watering Problems
This can be either too much (see my fixes for overwatering) or too little watering. For plants that are not getting enough water, you’ll actually see wilting as the first symptom. Without the water pressure inside the plant, it droops.
After that, there can be yellowing before they lose the leaves entirely.
Check on the water needs of your plants, and then double-check you are not giving too much or too little. Does the soil stay wet or soggy for too long after you water the plants? A lack of drainage could start to water-log the roots even if you are actually watering them correctly.
It might seem like a positive thing that the soil holds on to water so you aren’t getting out the watering can every day, but its not a great situation for plants because their roots do need to breathe.
If drainage is the case, you will want to consider repotting the plant in looser soil or potting mix that provides better drainage. Materials like peat moss, shredded coconut fiber, sand or perlite are all good options.
4 – Environmental Shock
Plants generally do best in a relatively constant or at least seasonal environment. Some types of changes can shock them, leading to yellowing and dropping of leaves. As long as the change isn’t a hazard to the plant, it will certainly recover with a little added care.
One possible shock is that you’ve recently repotted your plant. It’s not that you necessarily did it any harm, it’s just that the sudden change in soil chemistry and even just having more space for the roots can trigger a surprise for the plant. It should be fine with a little time.
Another possible shock is a drop in temperature. Not all plants are super sensitive to temperature changes, but there are some indoor plants that are not happy to get chilled.
Check your plant area and see is something has changed. Too close to an air conditioning vent, a newly opened window or anything else that would bring the temperature down from where it used to be.
Now in this case, you want to find the source of the draft and fix it, rather than hope the plant adjusts (it probably won’t).
5 – Insect Pests
By now, you have probably solved your problem of leaves turning yellow on your houseplants. If not, there is still another possible cause: insects.
You might think that if you had bugs in your plants, you would notice but they can be masters of staying hidden under the leaves, especially if you have a large indoor garden area that is packed with plants.
Insects that suck sap out of your plant are the problem. Aphids are one example that many indoor gardeners have had to deal with. They are small and translucent, and have a sneaky habit of clustering on the undersides of the leaves where you don’t realize they are there.
Though tiny, when you have enough of them, they can start to seriously drain the fluid from your plants. This creates the same situation of having too little water, as we mentioned earlier.
Use a spray of insecticidal soap on any aphids you see, and it should clear up the problem quickly. You will have to give your plants a close exam to make sure you get them all though.
For more tips to rid your plants of bugs, see my detailed article on controlling indoor plant pests.
6 – Broken Stem
When a stem gets bent suddenly, it may crack somewhat inside without showing a break on the outside.
Water stops flowing to the rest of the stem, and you get yellow leaves and wilting. But only where the damage is, so it kind of stands out that only one single section is suffering. You can just snip it off with clean scissors and your plant should be fine.
7 – Nothing is Wrong
Individual leaves on a plant do not live forever, and will often turn yellow as they die off naturally. They’ll tend to be the older leaves, and the rest of the plant will be doing fine.
Are you growing plants that may have variegated leaves? Sometimes new leaves start out green and slowly develop a mottled yellow/green pattern as they mature. If you’re not expecting it, it can make it look like your plant is unhealthy.
Your yellowing leaves may not be less of a mystery yet, though now you have a few different things to look at more closely to get things greening back up again. With all these possible issues, you should be able to easily diagnose your problem.