Why ZZ Plant Leaves Turn Yellow and How to Fix It

The attractive Zamioculcas Zamifolia, or ZZ plant for ease, is a famously low-maintenance houseplant that originates from Eastern Africa. It is very tolerant to both mild drought conditions and low light levels making it a great choice for novice house plant enthusiasts.

However, it is important not to confuse low maintenance with no maintenance and if the leaves of your ZZ plant turn yellow it is a good indication that something has gone off-kilter. Let’s explore all the possible reasons for the colour change and how they can be remedied.

The Reason ZZ Plant Leaves Turn Yellow

Yellowing leaves on your ZZ plant are the tell-tale sign that a condition called chlorosis has occurred. This happens when the chlorophyll within your plant has been impacted. 

Chlorophyll is located within the tiny structures of plant cells, known as chloroplasts and is the most important component of the photosynthesis process. 

It is responsible for absorbing sunlight which is then ultimately converted into energy. Chlorophyll cannot absorb the green wavelengths of sunlight, so this green light is reflected giving plants their green pigmentation.

There are many external factors that can cause the cells within a plant to be damaged therefore impacting the ability of the chlorophyll to absorb the sunlight and reflect the green colour. The plant will then appear to develop an unhealthy yellow hue: the sign chlorosis has appeared.

Watering issues, excess light and nutritional problems will all cause damage to chlorophyll in ZZ plants and turn the leaves yellow. Each reason will present other distinct indications to enable you to better identify the cause.  

I do find ZZ plants to be very robust and it should be noted that issues are rare. If you use my guide to identify the exact trigger for the chlorosis and carry out my recommended fix, you should be able to restore your ZZ plant back to its emerald-green glory.

What Causes ZZ Plant Leaves To Turn Yellow

Unlike other higher-maintenance house plants, there are six core factors that cause yellowing leaves in ZZ plants. Here below you’ll find my insight into each of these issues along with an explanation of ways you can fix them and prevent them from re-occurring.

Watering Problems

Watering issues are the main cause of chlorosis in ZZ plants. 

ZZ plants have well-established root rhizomes which allow them to store water and nutrients. This function allows them to cope with minimal maintenance and extract as much as they can from the water they receive. 

However, they can quickly become overwhelmed by excess water and start to drown in their own pot as their rhizomes become full.

Excessive Watering

If your ZZ plant is starting to turn an unhealthy shade of yellow or light brown at the leaf tips then it would be safe to assume that your plant has been exposed to too much water. 

This might also be accompanied by soggy soil when pressing your finger into the pot.  When soil is too wet, water will pool in the plant’s rhizomes as well as in the soil meaning insufficient oxygen can be absorbed by the plant cells. This in turn can cause chlorosis to set in. 

ZZ Plant Leaves Turn Yellow - ZZ plant leaves suffering from over watering
ZZ plant leaves suffering from over watering

Classic overwatering is the most common cause. If there are just a few outlying leaves turning yellow, you should let the plant dry out completely then resume watering every 2 to 3 weeks as the first port of call. 

Check the size of the pot’s drainage holes too. They could be blocked which can cause water to pool. 

Snip away the few yellow leaves near the stem and soon your plant will be back to its former glory.

Root Rot Caused by Excessive Water

If you note yellow leaves and soggy soil plus a musty smell, mushy leaves, stunted growth and possible leaf drop it will likely indicate that root rot has set in. 

To be absolutely sure that this is the problem, you will need to remove your ZZ plant from its pot and inspect the root network. 

Be gentle as the ZZ plant can be damaged by handling. I advise flipping the pot upside down and sliding it out. Healthy roots are white and firm. Any brown, grey or slimy sections indicate it is a casualty of root rot. 

If the entire root network is brown then the plant should probably be disposed of, but if sections of white remain you will need to urgently re-pot to revive your plant.

Using a sharp, clean and sterile pair of scissors prune back the brown sections of root to leave just white healthy roots. 

Then, repot in a clean pot with good-sized drainage holes. Always replace the potting soil where your plant has suffered root rot as the old soil could contain disease and bacteria that could re-infect the roots after re-potting.

Compost needs to be light and well-draining compost and the RHS recommends a sandy loam mix for ZZ plants

Trim away any yellow leaves or stems as these won’t recover and your plant will look all the better. 

Your resulting plant might only be a third of its former size, but it will give it the best chance of survival. Resume a 2-3 week watering schedule and always check that the soil is dry beneath the top 2-3 inches before watering.

Underwatering

If your ZZ plant leaves have started to show yellow tips or have turned a full shade of yellowy-brown, especially on the lower leave, chances are, your plant is trying to conserve water. This discolouration is usually accompanied by the appearance of crispy leaf edges too.  

This is a less likely reason for yellow leaves as ZZ plants can manage a lot of neglect, and it is quite rare for this to occur. 

Symptoms of underwatering also go hand in hand with bone-dry soil that has come to resemble dust.

The remedy here is simple, you need to give your plant a thorough and deep drink. 

I like to remove my ZZ plant from its decorative pot and place it in the sink. That way I can water thoroughly and wait to see the excess water run freely from the drainage holes.  I then wait until water stops seeping through the holes. There’s no chance the root system can absorb more moisture than required away. 

Snip away at the shrivelled leaves and ensure your ZZ plant receives a drink every 2 to 3 weeks moving forwards. 

Yellow tips are the first indication the plant needs water
Yellow tips are the first indication the plant needs water

Excessive Sunlight Exposure

The second most common cause of yellow leaves on your ZZ plant is excessive light exposure. In fact, one of the reasons they make such a great, low-maintenance house plant is their ability to tolerate very low levels of light. 

If you are sure the watering schedule is on track, yet you notice yellow or brown patches on the leaves and your plant is located near a window it could be down to sunburn. 

ZZ plants are especially prone to this in the summer months so consider moving them to an area with lower levels of light. These plants can survive surprisingly well even in a windowless office, taking the light they need from the fluorescent light tubes

Fertilizing Issues

Much like with overwatering, it is quite rare for a ZZ plant to show symptoms of a nutrient deficiency. It is much more likely that over-fertilizing is to blame. 

ZZ plants require very little fertilizing and can even tolerate no fertilizer at all if the soil has some degree of nutrients contained within it. 

If you do want to fertilize your ZZ plant – perhaps it has been in the same pot for more than a year – use a water-soluble or liquid fertilizer with a low NPK such as a 2-2-2 or a half measure of 10-10-10. 

Fertilize infrequently, and only during the active growing season (April to October). 

Overfertilization 

Your ZZ plant may be suffering from fertilizer burn if you have been feeding it more than once every 6-8 weeks and/or you have been using a highly concentrated NPK formula.  

However, it is worth ruling out excessive light exposure issues or water problems before taking any action. 

If you have ruled out other possible causes and you suspect overfertilizing to be the case, you will need to flush the soil with water and then let the soil dry out. In severe cases, it is worth re-potting and replacing the soil. 

Refrain from fertilizing again for at least 6 weeks before re-commencing a less zealous fertilizing regime. This means halving the frequency or strength of the feed you were previously using and only applying it twice during the growing season. 

Under Fertilization 

If you have never fertilized your ZZ plant, then it is possible that yellowing leaves could indicate that your soil that has become nutrient-depleted. To be sure, I recommend conducting a soil pH test before taking any course of action. 

If a soil pH test confirms a nutrient deficiency – most likely a lack of either nitrogen, phosphorous, or potassium – then I recommend you fertilize your ZZ plant with an evenly balanced fertilizer such as 2-2-2, 5-5-5 or 10-10-10 NPK. 

A liquid fertilizer is best for ZZ plants mainly because it is difficult to mix granules evenly into the soil around the root structure without causing damage. 

Combine a liquid feed with water and apply when your plant next needs watering. Avoid repeating this too frequently. I find that just two or maybe three times during the growing season (spring through to the fall) is sufficient.

Under fertilizing ZZ plants is relatively uncommon, so apply with caution and check all other factors and causes of yellowing leaves first.

Old or Spent Leaves

With a life span of an average of 10 years, it is no surprise that ZZ plants will go through a natural process of leaves ageing and dying. Typically, these leaves will turn yellow as cell structure ages and breakdown beyond repair, causing them to eventually fall off.

Yellowing leaves, especially near the base of the plant are a good indicator of spent leaves. Be sure to rule out other causes such as watering problems, light exposure and over-fertilizing first. 

Chances are these leaves have just reached their natural peak and are ready to be pruned away. Trimming them off will provide a cleaner look to your plant and will allow all growth and nutrient absorption to go into the younger, fresh leaves.

Old leaves turning yellow at the base of the ZZ Plant
Old leaves turning yellow at the base of the ZZ Plant

Stress from Repotting

Repotting is a tense process for any plant. I often liken it to moving house! There is a new environment to get used to, the move consumes a lot of energy, and generally, after the process is complete you feel totally and utterly stressed! 

If you have recently re-potted your ZZ plant and you start to notice the leaves yellowing or the plant just generally looking a little sickly, then it may just be the impact of the pot and soil change. 

Your plant should bounce back quickly, and it is best left to embed in its new home. It is important not to get tempted into over watering or over fertilising or generally over fussing as this will exasperate the issue. 

Carefully trim away yellow leaves and then just let the plant rest and get used to its new environment. It may need 1-2 months to fully recuperate.

With this in mind, the ZZ plant should only really be re-potted if it has become root bound or you need to change the soil after root rot or such.

FAQ ZZ Plant Turning Yellow

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Ben's horticultural interest grew when graduating from Hertfordshire University in 1997. Having contributed to numerous publications including Better Homes & Gardens, Garden Design Magazine, and The English Garden. He is also the author of Propagating Houseplants Made Easy.