Although ZZ plants are particularly well-known for being resilient and easy-to-maintain plants, they, too, have moments of suffering and might need your help, “Why is my ZZ plant turning yellow,” you might ask – it’s crying out for support!
As it happens, there are multiple reasons why your ZZ plant may be turning yellow, and it’s crucial to find the source of the problem as soon as possible. In my experience, ZZs are easy to bring back to full health, provided you act fast.
With that in mind, let’s take a look at some of the most common reasons for ZZ plants to go yellow and see what you can do to get them back in ZZ top-tip shape!
Reasons why your ZZ’s going yellow
ZZ plants are pretty hardy and will take low light conditions fairly well – but if your specimen’s starting to look a bit peaky, here’s what you need to look out for.
It’s getting too much sunlight
One of the most common reasons that ZZ plants turn yellow is that they have been exposed to too much sunlight.
People, especially amateur gardeners, partly love these plants because they are resilient and thrive in low light and brighter conditions. They’re fantastic bathroom plants, for example.
But, they do have a major issue with direct sunlight.
If your ZZ plant is in a space where it gets more than four hours of direct sunlight daily, then you can link the yellowing leaves to an overdose of vitamin D.
Usually, a ZZ plant in too much sunlight gets brown patches or dried tips due to the leaves burning, but they have been known to go yellow, too.
The best remedy in this situation is to move your ZZ plant to a spot where it does get some light, but not beaming directly onto its leaves.
In my experience, simply moving a ZZ plant somewhere a little shadier can do enough to bring it back from ill health.
You’re overwatering it
ZZ plants don’t need watering often. In fact, another reason why they are so good as starter plants is that it doesn’t really matter if you forget to water them every now and then! They can manage perfectly well in dry conditions.
However, that does mean that they tend to suffer when they get watered too much.
When ZZ plants are overwatered, it can easily lead to root rot – which, as any experienced plant parent will tell you, can be a nightmare to contend with.
That said, the fault may not be entirely yours. You may find that you are watering the plant sparingly enough, but the soil it’s in is the issue. If the soil isn’t draining well due to its composition, or even the pot, it will retain more moisture.
When the plant is suffering from root rot, it isn’t getting the nutrients it needs and will start to fail, hence the yellowing leaves.
Before taking any drastic measures, knowing what you’re dealing with is important. Start by checking the soil to see if it is wet. If the soil feels moist or damp, and you haven’t watered it too recently, you’ll need to take the plant out of the pot.
Remove the soil carefully from around the roots so as not to damage them. Ideally, the roots should be completely white. If they are brown in parts, or emit a foul smell, then you definitely have root rot.
Take sharp pruners and cut the root rot away from the affected roots. You can also cut incisions into the healthy roots, which will encourage new growth.
Just be careful not to cut all the way through, and always wash the pruners after dealing with the root rot, and before you use them again on any healthy roots!
Once your plant is back to normal, place it back into the pot, ensuring it’s in well-draining soil and a pot with enough drainage holes. Even if the old soil seemed aerated enough, it’s still worth replacing it as it will carry the rot.
Once the plant is potted, slightly water it to moisten the soil, then wait for the soil to dry out completely before watering again!
You should only water your ZZ plant every two to three weeks. The only way to know if it needs a drink again is by checking the soil and ensuring that it is indeed completely dry.
You’re underwatering it
Since ZZ plants don’t need a lot of water and tend to keep thriving in arid states, it can be easy to forget to water them at all. And, while they can manage being underwatered for a little while, yellowing leaves will occur if such conditions persist. Eventually, the leaves will wrinkle and fall off the plant.
Avoid this by, first of all, feeling the soil. If it is bone dry, then it’s certainly in need of a drink.
However, it’s important not to overfill the plant with water straight away – this can easily lead to overwatering and – of course – dreaded root rot.
So, instead, water your ZZ well but remove any excess water from your drainage saucer so that the plant does not sit in it.
Then, try to set a reminder for yourself on a calendar or smartphone to remember to water the plant. Ideally, you shouldn’t have to wait for it to go yellow before you remember that the poor thing needs a drink!
Adding water-soluble fertiliser is a great way of ensuring it gets a good balance of watering and nutrition.
Handy tip! I always recommend using dechlorinated water wherever possible, and no matter the plant. Dechlorinated water is free from some of the nastier leftover chemicals and impurities you’ll get out of the tap.
To dechlorinate your water, simply fill a container or jug out of the tap and leave it to stand overnight. Ideally, you should leave it for up to 24 hours for the best results.
Alternatively, if you have a water filter jug or similar setup, you’ll get fresh and safe H2O just as easy – albeit a lot quicker!
It’s not getting enough fertiliser
As with all living things, ZZ plants need a good amount of nutrition. A poor diet can lead ZZs to turn yellow – which means your specimens may be suffering from a nutrient deficiency.
ZZ plants need fertilising about once a month. You can use an easy-to-apply, water-soluble fertiliser when watering them next.
When applying, follow the instructions on the carton or packet carefully. Applying too much can also cause nutrient burn, which will have even more detrimental effects.
It is also worth noting that if you have applied fertilisers more than once a month, you could have already caused nutrient burns.
In this instance, the best thing to do is flush the pot out using clean, warm water and washing up liquid. You may even need to repot the plant in new well-draining soil to help it get a better start.
It’s at the wrong temperature
ZZ plants originate from Eastern Africa, so they like warmer temperatures. Ideally, they should be in a room that remains between 15 and 30º C. Anything lower than that is too cold, and the plant will start showing signs of suffering.
Conversely, anything warmer than that can be too hot for the plant. However, generally speaking, most of us don’t keep our homes at temperatures warmer than 30 C, so it’s not likely that your plant is yellowing because it’s too warm.
Just try and keep your plants out of any stuffy greenhouses, and if you’re hitting a seriously hot stretch, try and move them somewhere cooler for a little respite.
The room’s not humid enough
Although ZZ plants don’t need watering too much, they enjoy being in a relatively humid environment. They pretty much thrive in the same environments as we do, but occasionally they suffer in super-arid conditions.
For example, you might be experiencing a particularly hot summer, or the heating may be set too high on the thermostat!
If your ZZ plant has yellowing leaves, then it could be worth placing a humidifier in the room, or simply moving it elsewhere in the house – such as the bathroom or kitchen, for example.
You can also place other plants in the room with it to help increase the humidity. Just make sure your companion plants are likely to accompany ZZs without any detrimental effects.
It’s suffering from pests
ZZ plants occasionally suffer from pests – which, as all indoor gardeners know, is a major source of frustration. The most common pests to infect ZZ plants include mealybugs, scale, fungus gnats, and aphids.
If your ZZ plant has any kind of tiny bugs on them, the first thing you need to do is separate it from your other plants and isolate it.
Ensure your other plants haven’t been affected, or they’ll need treatment immediately. The problem with pests is that they multiply lightning-fast. If you don’t act quickly enough, then your other plants will get worse than just yellowing leaves.
In most cases, pests can be dealt with using insecticidal soap – however, aphids are best treated using water and a few drops of washing up liquid.
Remember to gently wipe all of the leaves, both on top and underneath, and the stems. In some cases, you may need to replace the soil or growth medium completely if there are pest eggs deep down.
It’s getting old
Just as our hair changes colour as we grow older, so too do certain leaves on plants! And that’s no different for your ZZ plant. Thankfully, this isn’t a bad thing. It just means that your ZZ plant is getting rid of the older leaves to make room for new ones.
A good sign of ageing is that the yellowing leaves are generally closer to the base of the plant, and you have some new growth closer to the top.
It’s also good to rule out all of the other potential issues before you decide that it’s probably just ageing, in case the problem gets worse before it gets better!
Yellowing leaves could also signal that your ZZ plant is root-bound. If you noticed that your plant was at one point growing healthily on top, it’s important to remember that it will have been growing really well beneath the soil, too!
So, it could simply be that the plant has grown too big for the pot – and another good sign of a plant being root-bound is that you notice roots growing above the soil. Then, it’s time to look at what’s going on underneath.
Thankfully, the issue is pretty easy to deal with, and all you need to do is repot the plant in a bigger container. Be sure to carefully prune away at any roots that aren’t looking healthy, and mix up some fresh medium.
ZZ plants – for all they are pretty robust and don’t tend to need much fuss – can turn yellow for a variety of reasons. Yellowing leaves is simply a warning signal to show us that we need to take better care of them in one way or another.
To avoid your ZZs yellowing too much, do follow our guide above – and when you’re confident enough to start growing more of these beauties, why not start propagating ZZ plants, too?