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How Do Bonsai Trees Stay Small? (Why?)

The real appeal of bonsais is that they are small. 

But, have you ever wondered how a person keeps a tree that normally grows huge as a tiny plant?

Bonsai trees stay small because growers keep them in restrictive containers and prune their roots to constrain their growth.

If left to themselves, these trees would grow as large as any other tree of their kind because they are not naturally small.

In this article, we will examine how people keep their bonsais small. 

Why Are Bonsai Trees So Small?

Bonsai trees are small because people keep them in tiny containers and prune their roots so that they don’t stretch out. 

Without a large, established root network, the tree cannot grow big

In this case, the plant simply cannot collect enough food and water to sustain large amounts of growth.

Thus, with tiny roots, the tree can only take up a small amount of water and nutrients at once. 

And since the plant needs food and water to sustain existing growth as well as to create new development, the tree will remain small.

Bonsais also cannot grow quickly because of their limits, meaning that over the course of the tree’s life, it can only gain a certain amount of size.

If a person did not restrict a bonsai tree’s roots, though, the tree would grow to normal size, whatever that might be for its species.

People can even train large trees to grow as tiny bonsais if they begin the process when the tree is young. 

Overall, by pruning the root network and preventing it from growing too large in any direction, the tree remains miniature.

Do You Have to Keep a Bonsai Tree Small?

If you want your tree to remain a bonsai, you must keep it small.

Anything over 80 inches (203 cm) in height is no longer a bonsai. 

Instead, it is a small tree. 

Of course, there is no obligation to keep a bonsai tiny if you’d rather not. 

You can plant one in your garden and allow it to grow into a full-sized tree if you prefer.

However, if you wish to keep the tree in your home and retain it as an ornament and expression of art, you will need to keep it small.

And generally, if you want it to count as a bonsai as far as the international bonsai community is concerned, it must be less than 80 inches high.

Why Are Bonsai Leaves So Small?

It’s hard to say why bonsai leaves are so tiny. 

But, most likely, the leaves stay small because the restricted conditions mean the plant puts fewer cells into each leaf as it starts to develop them. 

Thus, the leaves are smaller because of the reduced number of cells they have. 

And, of course, bonsai leaves can be much smaller than those on a regular tree. 

For example, deciduous bonsai trees often produce leaves as much as 50 times smaller than they would otherwise be. 

Meanwhile, a coniferous bonsai tree’s needles might be about an eighth of the usual size.

This happening is good for those who wish to grow bonsai trees because it ensures the leaves look in scale with the trunk and branches.

If the leaves grew to the standard size, they would look out of proportion with the rest of the tree.

However, you should note that the leaves can be oversized in some cases, much closer to a typical leaf for the species.

To deal with this problem, growers often implement a technique called defoliation.

This process involves removing some or all of the leaves the plant produces during the growing season, encouraging it to put its energy into a second flush of growth.

And this second growth is usually much smaller than the original one, meaning the leaves look more in proportion with the rest of the tree.

But, you should be aware that this will only last for one season. 

The following year, the new leaves will be large again.

Therefore, growers usually use this procedure only when taking their bonsais to shows or competitions. 

Do Bonsais Produce Small Fruit?

Interestingly, a bonsai tree that produces fruits will usually create ones that are not miniature.

These fruits might be slightly smaller than the standard size, but the difference will be minimal.

So, generally, a bonsai creates fruits that are normal in size.

This fact can be a problem for growers, though, as large fruits look out of proportion and can easily damage the tiny tree.

So, many growers choose trees that have naturally small fruits, such as cherries, because these fruits will simply look like apples or other large fruits on their scaled-down tree.

Why Do Fruits Stay the Same Size on a Bonsai?

Fruits stay the same size on a bonsai because the genetic information within the tree remains the same. 

Thus, the fruits come out the same size as they normally would. 

Can Trees Naturally Remain as Small as a Bonsai?

Many people might think that a bonsai tree could never occur in the wild. 

But amazingly, there are a few unusual specimens that people have discovered in the natural world.

Explorers often find these trees on cliff faces, growing in highly constricted conditions in the rocks, where their roots cannot spread out. 

The trees, therefore, grow in perfect miniature, just as they would do in a bonsai pot.

Yet, this sort of bonsai tree is extremely rare, and you’ll probably never see one in the wild. 

So, naturally, many bonsai enthusiasts want them because of their uniqueness. 

And it is interesting to know that these tiny specimens can be just as healthy and resilient as a full-sized version of the tree.


Bonsai trees stay small because their owners encourage them to do so through pruning and root restriction. 

Thus, overall, a bonsai tree cannot grow large because its root network is not big enough to sustain lots of growth, forcing it to stay tiny.

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