Seeing a yellow leaf on one of my plants always gets my attention. And if I’m being completely honest, when I first started growing indoor plants, my immediate thought was usually, What have I done wrong?
But over time I’ve learnt that one yellow leaf doesn’t necessarily mean something terrible is happening. Sometimes it’s simply an older leaf reaching the end of its life. Other times, your plant really is trying to tell you that something in its care needs adjusting.
The important thing is not to panic or immediately reach for the watering can! Instead, I like to look at where the yellowing is happening, how the leaf feels, how wet the potting mix is, and what has changed recently.
Here are the seven things I would check first.
1. Too much water
This is always high on my checklist.
The problem isn’t necessarily that you gave your plant too much water in one go. More often, it’s that you’re watering again before the potting mix has had enough time to dry.
A plant sitting in constantly wet mix can struggle because its roots aren't getting enough oxygen. If that continues, the roots can eventually become damaged and root rot can develop.
Look for yellow leaves combined with:
- Potting mix that stays wet for a long time
- A pot that still feels surprisingly heavy
- Soft or limp yellow leaves
- Wilting even though the mix is wet
- An unpleasant smell from the potting mix
If you're seeing several of these signs together, check the roots rather than simply watering again.
2. Not enough water
Here's where yellow leaves become confusing: too little water can also cause them.
With an underwatered plant, I would expect the potting mix to be very dry and the pot to feel much lighter. The leaves may also look limp, curled or crispy rather than soft and yellow.
This is why I don't like diagnosing a plant from the colour of one leaf alone.
Before deciding what to do, check the pot.
3. Not enough light
This is one that's easy to overlook.
A plant might survive in a darker corner of the house, but that doesn't necessarily mean it's happy there.
When a plant receives less light, it generally uses water more slowly too. That creates another problem: if you're watering it exactly as you did when it was receiving more light, the potting mix may stay wet for much longer.
Watch for yellowing together with slow growth, smaller new leaves, stretched growth or a plant leaning towards the nearest window.
Sometimes moving a plant to brighter indirect light can make a surprisingly big difference.
4. Your potting mix is staying wet for too long
You can actually have a sensible watering routine and still end up with problems if your potting mix is too dense for the plant or your conditions.
I prefer plenty of airflow around the roots of many of my tropical plants, particularly Hoyas and aroids.
But I don't believe there's one magic potting mix that works for every plant and every home. The right mix depends on the plant, the pot, your light levels and even how you tend to water.
The question I would ask is simple:
After I water this plant, is the mix drying at a reasonable rate or is it still soaking wet many days later?
Also check that your nursery pot actually has drainage holes and that water isn't collecting unnoticed inside a decorative cover pot.
5. The plant may need feeding
If your plant has been growing in the same potting mix for a long time, nutrition can sometimes be part of the problem.
But I wouldn't see a yellow leaf and immediately add fertiliser.
First check the basics: watering, drainage, light and roots.
If those all look good and the plant is actively growing, then think about when it was last fed and whether the fertiliser you're using is appropriate for that particular plant.
More fertiliser isn't automatically better. Follow the directions on the product you're using rather than trying to compensate for another care problem with extra feeding.
6. Check carefully for pests
Whenever something changes unexpectedly on one of my plants, I like to have a good look at the leaves.
And I mean a proper look.
Check:
- Underneath the leaves
- Where the leaf meets the stem
- Along stems and new growth
- Around tightly folded emerging leaves
You're looking for things such as webbing, sticky residue, tiny insects, unusual speckling or patches of damage.
If you find something suspicious, move that plant away from the rest of your collection while you work out what's going on.
7. Sometimes a yellow leaf is completely normal
This is probably the most reassuring one.
If it's one older leaf near the bottom of an otherwise healthy plant, the plant is growing well and everything else looks normal, it may simply be natural ageing.
Plants don't keep every leaf forever.
This is especially important because we can sometimes create a problem by trying to fix something that wasn't really a problem in the first place.
If the rest of the plant looks happy, I usually watch it before making any dramatic changes.
What the yellow leaf itself can tell you
Rather than asking only “Why is my plant yellow?”, look at the pattern.
Several leaves are yellow and the soil is wet
Check your watering frequency, drainage and roots.
Leaves are yellow and crispy
Look at underwatering, very dry conditions or potentially excessive light, depending on the plant.
The whole plant looks pale and growth has slowed
Look at its light levels, root health and nutrition rather than treating the leaf colour alone.
Yellow leaves have spots, webbing or sticky areas
Inspect carefully for pests or disease.
The pattern gives you clues. That's much more useful than assuming every yellow leaf has the same cause.
Australian seasons can change your watering completely
This is particularly important at this time of year.
During an Australian winter, many indoor plants are receiving less natural light and our homes may be cooler. That can mean the potting mix takes much longer to dry than it did in summer.
So if you've been watering every Saturday because that's what worked during the warmer months, your plant may suddenly be staying wet for far too long.
Then summer arrives and everything can change again.
That's why I prefer to check the plant rather than follow the calendar.
Feel the mix. Lift the pot. Look at the leaves. Pay attention to the light.
Your plants will tell you much more than your watering schedule will.
Should you cut yellow leaves off?
Once a leaf is completely yellow, it generally isn't going to become green again.
I usually prefer to wait until I'm confident the leaf is finished before removing it with clean scissors or secateurs.
But removing the yellow leaf isn't actually solving the underlying problem.
The real question is:
Why did it turn yellow?
Work that out first.
My simple yellow-leaf checklist
When I find yellowing on an indoor plant, this is the order I would work through:
- Check the potting mix. Is it wet or dry?
- Lift the pot. Does it feel unusually heavy?
- Look at the light. Has the plant been sitting somewhere too dark?
- Check drainage. Is water trapped in the cover pot or saucer?
- Inspect the leaves and stems. Any sign of pests?
- Think about feeding. Has the plant been growing for a long time without nutrients?
- Look at the whole plant. Is it actually declining, or is this just one old leaf?
Most importantly, don't change five things at once.
Make the most likely correction and then give your plant a little time to respond.
A yellow leaf is a clue, not a disaster
One of the things I love about growing plants is that you gradually learn to read them.
Yellow leaves used to worry me much more than they do now. These days, I see them as a reason to stop, have a closer look and work out what the plant is telling me.
Sometimes I need to change something.
Sometimes I just need to leave the poor plant alone!
If you're still building confidence with indoor plants, you can also have a look through my collection of easier-care plants.
And remember: don't diagnose from the yellow leaf alone. Look at the whole plant, the roots, the potting mix and its environment.
That's where you'll usually find the answer.
