Why Are The Leaves On My Bonsai Tree Sticky?

A good friend of mine asking me about why the leaves on his bonsai were sticky and what I do to about sticky leaves on my bonsai trees. In all honesty, I had to do some research because I had never heard of this before and certainly never seen it on my trees.


Sticky foliage on bonsai trees is caused by a scale pest or aphid infestation. The pests consume sap from the bonsai tree and secrete ‘honeydew’ as the sticky by-product. The insects are usually harmless and can be easily treated using soapy water and a vinegar solution. Let’ts find out more… 


Why Your Bonsai Tree Foliage Feels Sticky


It’s not your imagination and no, you didn’t spill a drink on your tree, it really is sticky. That’s unfortunately because of tiny scale insects or maybe even aphids. They’re pretty annoying it seems, all they really seem to do it suck the sap out of bonsai trees and other house living plants. Aphids and scale pests can’t do much damage to a bonsai tree, providing the tree is relatively healthy in the first place.


The sticky feeling is because of what the insects secrete, known to gardeners as ‘honeydew’. The majority of the time the owner would have no idea about the scale insects or aphids even being around as they’re sometimes extremely hard to spot – not the most obvious creatures. A bonsai tree can easily get infested with up to 200 of these pests, so that shows the scale of how small they are.


Aphids Or Scales?


Distinguishing which is on your tree isn’t really the most important thing in the world as they’re both treated in the same way, using the same few simple methods.


Scales are tiny insects, without wings, that live on the branches of bonsai trees. Aphids come in different colours, either brown, green, grey or red and they will usually not have wings. Aphids will tend to live on the underside of leaves, hence why they can be hard to spot initially until large amounts of honeydew are secreted.


I learnt a pretty cool tip from a friend of mine – look out for ants when routinely checking over your bonsai tree. It’s said that ants are usually present when the honeydew is around, due to them feeding from it. Take this with a pinch of salt because there have been many cases of aphids and scale pests infested a bonsai tree and no ants being around, it’s very situational.


How Does Your Bonsai Get Aphids?


I’ve learned that there are only two ways your bonsai tree can actually get aphids.


  • Your bonsai already had them – from a nursery stock plant or if you’ve bought the bonsai etc.
  • They flew onto your bonsai from outdoors.


Keeping your tree outdoors can obviously increase the risk of catching insects like aphids but still, as most bonsai enthusiasts would tell you, the rewards for having the bonsai outside greatly outweighs the risk of things like sticky leaves. There is really no way for you to stop the bonsai tree getting infested with aphids or scales as no matter how healthy the tree is, it can still happen.


What Can You Do About It?


Thankfully, this isn’t going to be the death of your bonsai tree. Scale and aphids, as annoying as they are, aren’t really too dangerous to the health of your tree in the long run. That being said, it’s still the best course of action to treat them as soon as possible to avoid any possible risks.


  • Take your bonsai tree outside.
  • Wash the tree gently with water, making sure you cover all areas including the branches and underside of leaves to remove the aphids.
  • Use a solution of water and a few drops of dish soap to cover the bonsai tree. This will cover the insects and kill them.
  • Use a wet cloth to wipe the tree down and remove the soapy water.


It’s really that simple. You should notice that over the coming weeks you won’t have any sticky leaves and leaves will stop turning yellow and dropping off. For a relatively small infestation of aphids, this alone should be enough to get the pests off your bonsai and your sticky leaf issue should stop there. For large infestations, it may not be enough so using another method maybe needed.


Another way to kill the scale and aphids, although I really wouldn’t recommend it, is to use vinegar. If you fill up a misting bottle one third with white vinegar and two thirds with water, when sprayed it will kill the insects instantly. People often use this technique with houseplants but in all honesty I wouldn’t be quick to recommend it with a bonsai tree, the best course of action, by far, would be the water with a few drips of dish soap.


If after a few weeks you are still having a problem, I would definitely recommend creating a forum post about it and seeking more help as it maybe worse than just scales and aphids. If you want a more immediate solution, taking your tree down to a local bonsai nursery can be a great idea – this has saved me a few times over the last few years! They are most likely to recommend using a pesticide on your bonsai at this point, if the soapy water and vinegar hasn’t proved effective enough.


It’s worth noting that a healthy bonsai is much less likely to have an issue withstanding diseases and insects that come its way. Prevention is the best policy. Ensure that you’re constantly keeping your bonsai tree healthy, pruned and consistently check for any infections or insects in the tree. Through the growing season when routinely pruning, check the bottom of most of the foliage as this would be a perfect time to spot any pests lurking.


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