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How Do You Trim The Roots Of A Bonsai Tree? (Step by Step)

Caring for bonsai trees is a unique art form, different from how you would manage other plants. 

Looking after non-bonsai plants involves re-potting them frequently to allow the root systems to expand, but bonsai cultivation is the opposite.

Since you will need to keep your bonsai tree small, you have to limit the size of its roots through root pruning. 

The first time you do this, you’ll need to give a significant cut to the taproot. 

Afterward, you should nurture the younger roots while removing the older and thicker ones.

Continue reading for a guide on the best root reduction techniques and practices.

Step By Step Guide for Trimming Bonsai Roots

  1. Remove your bonsai from its container and use your fingers to loosen the majority of the surrounding soil so that you can get a clear view of the root system.
  2. Trim the roots that circle the central taproot with a clean pair of pruning scissors.
  3. Reduce the length of the thick, vertical storage roots by around one-third. Leave the fine hair roots protruding from the central taproot.
  4. Trim away about one-third of the lower root system to create compact roots.
  5. Place the bonsai in a new container.
  6. One year later, repeat steps one to three of this process.

Why Do I Need to Trim the Roots of My Bonsai Tree?

It’s essential to trim the roots of your bonsai tree to prevent them from spreading outwards. 

If you allow the roots to grow unchecked, they will absorb more nutrients and end up a similar size as they would in their natural habitat.

But, of course, the idea of a bonsai tree is to produce a plant that looks like a miniature version of its full-sized species. 

And to achieve this look, you’ll need to maintain its root system to restrict the overall growth of the plant.

How Do I Trim the Roots of a Bonsai Tree?

When pruning the roots of your bonsai, the first step is to remove it from its pot and use a root hook to disentangle its ball of roots. 

Then, remove as much of the soil as you can with your fingers (if there’s a little leftover, don’t worry). 

Getting rid of the excess soil will give you a clearer view of the root system so you can see how much you can safely remove.

But remember that you should never cut off more than two-thirds of a root at any time.

Also, the first time you prune your bonsai, you need to use a saw to remove two-thirds of its taproot. 

The taproot is the central, vertical root that forms the system’s center. 

This root will be the one from which most of the other rootlets spring.

What Size Pot Should I Use for My Bonsai After Trimming?

After your initial trim of the root system, you need to be realistic about the pot size you’ll need to house your plant. 

Ultimately, you should think of picking a container like Goldilocks. 

You don’t want a pot so small that there’s no room for the plant to absorb water and nutrients, but at the same time, you don’t want your container so big that the roots spread out too far.

In general, aim for a pot about one inch taller than your pruned root ball.

Overall, getting the correct pot size is all about assessing your tree’s root system and finding the perfect fit that stops the roots from spreading outward but allows sufficient room for the plant to thrive.

Frequently Asked Questions 

What Is a Rootbound Bonsai?

The term rootbound refers to the condition in which a bonsai’s root system completely fills its tiny container. 

And while you should keep the roots cramped, a rootbound bonsai will not have enough room in its pot for water and soil, which it needs to survive. 

Thus, you should not leave a bonsai rootbound for too long as it will die. 

In this state, root trimming is important to avoid having to bring your tree back to life at a later stage.

How Can I Avoid Infecting the Roots of My Bonsai When I Trim It?

The best way to avoid infecting the roots of your bonsai when trimming is to ensure that you disinfect all tools before use. 

Disinfecting helps you avoid spreading foreign bacteria into your plant’s root system.

Stainless steel root scissors are the best option for a clean-cut, but you can use regular pruning scissors if you don’t have access to the former.

Additionally, to avoid damaging the roots of your bonsai, use a root hook or chopsticks when you comb out the roots. 

And don’t worry if there’s some soil left in the system. 

Leaving some soil is a much better option than washing it off with a hose or other pressured water source, which could cause severe damage to the roots.

When Do I Need to Trim the Roots of My Bonsai Tree?

Several factors affect how often you will need to trim the roots of your bonsai tree.

Firstly, it depends on tree species, as different trees have different watering routines and nutritional needs. 

Secondly, you need to take into consideration the depth of your container. 

A shallow container needs to have its roots pruned more often than a deeper one.

Third, keep in mind that the environment impacts your bonsai’s growth.

For instance, bonsais that live in hot, sunny climates grow faster than those in colder temperatures and therefore require pruning more often.

Additionally, you should avoid trimming the roots of your bonsai during the growing season. 

And depending on the species of your bonsai tree, the growing season lies between April and October.

There are some exceptions to this rule, though. 

If the leaves of your bonsai are turning yellow or displaying other signs of chlorosis, you may want to make one of two more significant cuts to its root system.

How Do I Trim the Roots of My Bonsai When Transferring From a Nursery Pot?

When you’re transitioning between a nursery and a larger pot, it may be difficult to trim the required amount of roots all in one go. 

So, instead, complete this process in stages. 

But, avoid making this transition too quickly, or you’re at risk of damaging the plant.

How Do I Maintain the Root System of My Bonsai?

Maintaining the root system is a crucial factor in keeping your bonsai small. 

To do this, start by gently lifting your plant from its pot and teasing away excess soil with a root hook. 

Then, trim straggly roots with pruning scissors. 

Afterward, place your bonsai in an appropriately sized pot.

You can carry out a maintenance prune every couple of months, though you should only conduct a structural pruning once a year, outside of the growing season.

Final Thoughts

If you’re a beginner at bonsai cultivation, root trimming may feel intimidating. 

Deciding how much or how little to cut off your plant’s roots can significantly impact its overall health. 

So, begin by taking small steps. 

Then, as your confidence builds, you’ll be able to trim roots like a pro.

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