Help! My leaves are going yellow.
This is often the first sign that your plants may be unhappy but its not always the case. There are several reasons why the leaves of your plant may go yellow ranging from watering issues to simple old age. The trick is to work out which one it is and act appropriately to fix the problem.
Water
The most common reasons for yellowing leaves are in my experience related to either watering or lighting, lets discuss watering first.
Unfortunately yellowing leaves can be a sign of both over and under watering, telling which one is the culprit is not as easy as it appears. If your plant has been underwatered its leaves will start to yellow and then proceed to brown and become dry and crispy. If its truly dried up the leaf will often crumble into dust between your fingers. A sign of under watering that occurs before the leaves start to lose their colour is wilting leaves and very dry soil, your plant pot will feel light if you pick it up as well. Overwatering will give you yellow leaves that are soft to the touch and if they go brown this will be mushy. Rather bizarrely the plant will also wilt if it had too much water. Check the soil; if it is wet or soggy to the touch you are definitely watering too much. There is more detail on watering on another post of mine “The great watering conundrum” where I discuss how I remedy the problem.
Too much light
Finding the correct balance of lighting to suit your plant can be tricky in the home. Placing plants in a window that receives direct sunlight through the middle of the day when the sun is at its strongest can lead to scorching, but place them too far away from your a window and you will see them suffer from lack of photosynthesis. If the leaves are going yellow from the edges inwards this is generally a sign of scorching and your plant may be getting too much direct sunlight. I think that most plants are happy in a window where they can get as much light as possible, but direct sunlight, especially through glass, can very easily scorch the leaves of your plants. Adding some shade netting over your window if it is south facing will help or just place your plants back by several feet. I keep most of my plants in a window that faces South East, this gives them some direct sun in the morning before it gets too strong and then the light for the middle and second half of the day is bright but indirect.
Old Age
Simple old age will cause your leaf to yellow, usually this occurs from the outer edge of the leaf and work is its way to where the blade meets the petiole. A really good case to observe this is in Alocasia or Colocasia. The plants in my collection will happily sustain between four and five leaves with each new leaf growing larger then the last. The new leaves take a lot of energy to produce though and so the plant will sacrifice the oldest leaf once the new one has hardened off. These old leaves will wilt and go yellow as the plant absorbs what ever nutrients is can from them before they shrivel and die. This is just part of the natural process and nothing to worry about; nothing lasts forever and your plant leaves are no different, as new growth emerges old growth is allowed to die off. You can see a great example of this in the picture at the top of this post. I think there is something quite beautiful about leaves that are dying of old age as they transition from green to yellow…maybe that’s just me?
Nutrients
This is a tricky one to diagnose and in my experience it is more likely that a plant will suffer from too high a concentration of nutrients rather than too little. Let me explain: fertilisers that we all use on our plants are great but the concentration/recommended dosage in my opinion is often too high and the temptation to use them more often that recommended is also a factor. When I started to collect houseplants, I followed the advice on the bottle and often added a little more because “what harm could it do”? Well it turns out quite a lot actually. As the water in your plant or the potting mix evaporates, the salts are left behind and its these salts that cause the damage – primarily yellowing leaves and burnt roots. Ensuring that you completely flush your plants substrate regularly will help to remove excess salts that have accumulated in the soil.
Pests and diseases
A physical attack by pests and disease will also cause the leaves to go yellow. Pests like Thrips, Mites and Aphids amongst others, are literally sucking the life out of the plant. The general reduction in the health of your plant caused by either pests or disease will often result initially with the deterioration of the foliage, spots and wilting or drying out of leaves altogether. Issues with the roots of your plant like root rot will first become visible in the foliage of your plant. When there is damage to the roots of your plant, it is unable to absorb nutrients and water correctly.
As you can see from my ramblings above there are lots of different things that can cause your plant leaves to go yellow and finding the issue that is effecting your plants sounds difficult so here is the checklist that I use:
- Is the potting mix wet or dry? This will indicate whether your are over or underwatering your plant. If its just right then go on.
- Is the leaf going crispy at the edges with patches of yellow? This is usually a sign of excessive direct sunlight.
- Is the rest of the plant healthy and growing well? This could well be a case of old age and is nothing to worry about.
- Are the leaves drying out and curling at the edges, looking burnt? If you are using a fertilizer this could be a sign your are overusing it.
- If none of the above apply and your plant is generally loosing its mojo then its time to check the roots for rot or damage.
