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Phototropism And Why Its Important To Rotate Your Bonsai Tree

Updated: Jan 7, 2023

What Is Phototropism and why can it affect my Bonsai Tree?

Chinese elm bonsai

This weeks article will be short and punchy but it will give you something important to think about. We are talking about phototropism which essentially in simple terms is how your tree and its branches will want to grow towards the light A.K.A the sun!

In not so simple terms phototropism occurs when the auxin in a growing tip favour's the side of the stem that gets the most light and causes the stem to grow in that direction in order to maximise its photosynthetic efficiency. If left alone like this you can end up with a tree that looks like its caught in the middle of a Mexican wave or is caught permanently in a heavy breeze pushing all the growth in a single direction ( this is great if you want a windswept design).

Phototropism can also cause havoc in our trees if we are growing out a new branch and we have not wired it yet, the branch may want to grow straight up towards the light but you want to wire your branches down. This means when it comes time to wire your new branch rather then taking the branch from a horizontal plane and bending it down slightly you will have to bend it down from somewhat of a vertical plane which can increase your chances of damaging a branch and will give you an unsightly C curve or tea cup handle on the shoulder of your branch.

So how do we avoid phototropism causing negative effects on our trees then? Don't get me wrong I'm not saying phototropism is a bad thing because its not. We just need to know how to control it.

For trees that are already styled and are in the maintenance stage you can avoid phototropism ruining your shape by rotating your trees every so often, by turning your tree either 90 degrees at a time or 180 degrees at a time you are exposing a different section of the tree to the area in the sky that you get the most sun through out the day. Most times if you look at your trees there will be a portion of the tree that is shaded most of the day while the other half will be soaking up that beautiful sunlight.

If you have a tree in development or you are trying to grow out a new branch as the shoot begins to grow and is thick enough to get some light wire on without damage you may want to wire it into a position that is close to what you want the end result to be. The wire should help stop the branch from wanting to grow straight up like it will naturally want to do. Be cautious though as wire on such a rapid growing branch can bite in quick so keep and eye on it and replace the wire as needed.

That is it for this weeks article, There isn't a whole lot to discuss about phototropism but if you didn't know about it and have noticed some of your trees seem to all look like they are growing in the same direction you now know why and know how to avoid this kind of growth in the future.

Until Next Time, Enjoy your Bonsai Journey.

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