Bonsai Fertilizer: Best Types and How to Use Them

When it comes to keeping plants healthy, one of the simplest ways is to match the nutrition requirements of each plant. 

For some plants, this will be feeding them every week during the summer or growing season, which suits plants like tomatoes very well. 

For others, such as succulents, the less you feed and water them, largely the better off they will be.

But what about bonsai trees, and their much larger, natural counterparts? In their natural habitat, the roots grow deep to extract what they need from the soil, and to help anchor the trees.

Of course, this cannot happen with bonsai trees. Bonsai trees stay in the same container, largely, for most of their lives. 

While it’s helpful to replenish the soil when the roots require trimming, this is not enough on its own to give a bonsai tree the essential nutrients to ensure healthy growth.

You need to feed them. But you need to be careful of how you do this, when you feed them, and what you give them. Feeding them too much or too little will alter the growth a bonsai is capable of.

Here’s everything you need to know.

What You Should Know About Bonsai Tree Fertilizer

Bonsai trees can seem extremely complicated to care for. But with the right knowledge, getting the conditions right for your bonsai to thrive isn’t difficult. 

One of the main ways of doing this is making sure to give your tree the appropriate nutrients, through feeding the soil. Fertilizer replaces those nutrients which the bonsai tree has already taken from the soil, allowing the bonsai to continue to thrive.

There are three components which make up any fertilizer, and that’s Nitrogen, Phosphorus, and Potassium, otherwise known as NPK. 

Different fertilizers contain different amounts of each, as each component does a different job. Potassium increases the plant health, Phosphorus encourages the roots, flowers, and fruits to grow properly, while Nitrogen promotes healthy leaves and stems.

Why should you feed bonsai trees? Well, it keeps the growth rate balanced, and each part of the plant growing as it should. Deficiencies lead to leaf loss, stunted growth, and overall worse-off plants which are susceptible to disease and pests.

Only apply fertilizer to the soil of the plant, never to the leaves. It can burn and kill the leaves if you’re not careful, and there’s also a risk of spreading disease.

Types Of Bonsai Fertilizers

Make sure you don’t use the wrong type of fertilizer, including a general one, as these will have different levels of those ingredients, but ones which don’t match up with exactly what the bonsai trees need. 

Always use a dedicated bonsai tree fertilizer, so you don’t under or overfeed your bonsai trees. Using the wrong type may burn the roots, which will lead to plant death.

Liquid Bonsai Tree Fertilizer

Liquid fertilizer especially formulated for bonsai trees is usually available in a concentrated form. 

This means that you need to dilute it in order to give the bonsai tree the amount it needs, otherwise it can be too strong and burn the roots.

The easiest way to do this is to keep a jug or bottle just for this purpose. This stops you overfeeding your bonsai, as the container will still have traces of the fertilizer left, and it also means that if you’ve mixed too much, you can leave it for a later date.

Once you’ve mixed it to the instructions on the specific fertilizer, you can apply it straight to the soil. Because it’s already watered down, you don’t need to wet the soil to stop the roots from burning.

How often you should feed your bonsai tree depends on the type of tree, as some are more demanding than others. 

Solid Bonsai Tree Fertilizer

Solid fertilizer for bonsai trees comes in powders, pellets, or granules. These types of fertilizer are usually much slower to release their nutrients, which eliminates the risk of the roots burning.

You can also visually see exactly how much fertilizer you’ve already put on, as it sits on the surface of the soil, so if you put too much on, just take it off. You still need to water it into the soil, though.

Again, how frequently you need to apply the solid fertilizer for your bonsai tree depends on the fertilizer itself (follow the instructions to begin with, and if it looks like your plant needs more or less, adjust accordingly), as well as the species of your bonsai tree.

What Type of Fertilizer is Best For My Bonsai?

Assuming that you’ve got a bonsai tree because you can dedicate a certain amount of time to care for it, it’s best to keep a close eye on your tree’s reaction to the care you give it.

If you feel you don’t have time to feed it, or if you travel a lot, it’s worth using solid bonsai fertilizer, as this has a much slower release than liquid fertilizer, and will largely do most of the work for you.

If you have more time on your hands, or want a more hands-on approach, go for the liquid fertilizer. It acts much quicker, but you will need to feed it more often, as every time you water the soil you wash out the fertilizer. 

Whichever you choose, make sure that you go for one which is suitable for your specific bonsai tree. It is no good getting a bonsai fertilizer for alkaline loving plants if you have an azalea, for example, as they are lovers of acidic soil.

Bonsai Fertilizers: Frequently Asked Questions

When Should I Start Feeding a Bonsai Tree?

It’s important to feed your bonsai tree regularly to make sure the plant is getting exactly the amount of nutrients it needs in order to grow properly. 

This needs to happen during the growing season, which starts in spring, until the later days of summer. 

The general rule is that you should feed it weekly during this period in order to keep it healthy, and slowly reduce the feed to once a month once the plant starts to slow down.

However, it depends on the type of tree.

Feeding Deciduous Bonsai

For trees that lose their leaves during winter, you should feed them once a week in their growing season, and stop completely when they drop their leaves.

Once the tree starts to wake up, you can start to feed your bonsai tree again.

Feeding Conifer Bonsai 

For conifer bonsai trees such as Spruce, feed them weekly, again, reducing this when the growth of the plant noticeably slows. 

As conifers don’t go completely dormant during the winter months, continue to feed them once or twice a month, gradually increasing the frequency as spring begins.

Feeding Subtropical and Tropical Bonsai

Feed tropical and subtropical bonsai trees every week during the height of the tree’s growth period. When autumn hits, reduce this to once a month until spring comes. 

It’s worth noting that many bonsai growers have had success developing their own methods of feeding, so try it and see what works for you. 

Don’t let your bonsai tree starve of nutrients, as this is a quick shortcut to an unhealthy plant, leaving it vulnerable to pests and disease.

It’s also worth mentioning that you should never feed a bonsai tree that looks ill, as the cause is probably something else, and you need to treat that first. 

Fertilizing an already-stressed bonsai tree can cause more problems than it solves, so hold back if you’ve just repotted your bonsai, if it’s dormant, or if it’s extremely dry. 

Wait a few weeks before you feed a bonsai tree you’ve just repotted. Don’t forget, you’ve already replaced the soil, so let it adjust to that first.

How Do I Fertilize My Bonsai Tree?

Make sure to follow the instructions on the specific fertilizer you’ve bought for your bonsai tree, as different brands may need different dilutions or measurements. 

Remember, you will cause more difficulties by overfeeding your bonsai. If it looks like you haven’t fed it enough, wait until the next time you should feed it, and add a very small extra amount.

If in doubt, you can also ask your local garden nursery, or a specialist bonsai nursery for guidance. 

Organic or Synthetic Fertilizer?

The first thing you need to know about fertilizer is that there are two types: organic, which is made up of natural resources, and synthetic: which are made up of different chemicals. 

Organic fertilizer is usually derived from manure, seaweed, or other organic matter which is high in nutrients. They are more environmentally friendly, and generally release those nutrients much slower than synthetic fertilizers, reducing the risk of root burn.

If you do choose to use synthetic fertilizers, make sure to avoid those which contain urea. 

While it is designed to replace the nitrogen levels required, it also contains a lot more nitrogen than some bonsai trees can cope with.

Tips and Tricks to Help Your Bonsai Tree Thrive

How to Recognize Signs of Overfeeding Your Bonsai

If you see an oddly colored layer sitting on the top of the bonsai soil which feels crusty, this is a sign that there is too much fertilizer in the soil. 

You’ll also notice that the leaves will begin to be affected, where they will yellow and start to die.

If a bonsai tree’s growth slows unexpectedly and out of season, or if the leaves drop prematurely, there’s a good chance that you’ve overfertilized the soil.

To help your bonsai tree recover, remove any part of the soil that has become crusted or oddly colored, flush out the soil with water, and replenish it. 

Make sure to cut off any affected leaves, and let your plant recover, holding off on fertilizing it for about a month.

Make Sure You Have The Right Fertilizer

This can be an expensive mistake. You don’t need to pay a lot of money to find a bonsai fertilizer suitable for your type of bonsai, but you do need to find the right one.

Ensure you get one that’s specifically formulated for your type of tree. Some bonsai fertilizers are very generic, and are only suitable for trees which go dormant in winter, or those which aren’t tropical.

Always Follow the Directions

Don’t use more fertilizer than the package recommends, as this can lead to overfeeding, making your plant stressed, and more vulnerable to pests and diseases. 

Be Consistent

You’d be surprised at what your plants can adapt to, if you give them the time to do so. This is why we introduce plants to a new environment gradually, if we take them inside or outside, only doing so for a few hours at a time. 

This allows the plant to acclimatize, and you should treat feeding your bonsai trees no differently. Make sure to feed them regularly, but if you find a specific fertilizer isn’t working, change it gradually.

If you’ve found a good schedule that your plant seems to thrive on, don’t change what isn’t broken.

Conclusion

Bonsai trees are largely an experiment, but a long-lasting and very rewarding experience when you get it right, and this includes knowing how to feed your bonsai tree properly. 

Getting the fertilizer right largely takes out some work in caring for a bonsai tree, as it will then have the nutrients it requires in order to thrive.

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