Why is my Pōhutukawa (Metrosideros Excelsa) not flowering?

Okay before we kick off here, there may be quite a few other reasons as to why, but in this blog post we are going to discuss and illustrate the fascinating morphology of leaf maturity.

The following images are taken from one single tree, all appearing on the tree at the same time. The images were taken around mid-spring and illustrate well the process the tree undertakes.

A juvenile shoot, notice the light green leaf colour and glossy texture. The stem and bud itself are also generally quite red and green. There are some great articles/ research papers out there to read, some documenting the increase in nitrogen found in juvenile shoots, which makes sense considering that Pōhutukawa’s are known to produce vigorous epicormic shoots in response to stress inhibitors. What is a stress inhibitor? I’ll expand on this a bit later in the post.
A juvenile shoot starting to morph into mature foliage. Again notice the change in colour and texture, more fine hairs (tomentum) appearing on the leaves. Prior to the leaf emerging, the bud colour and shape is clearly different too.
The semi-mature foliage. The leaves covered in tomentum. Noticeably different to the juvenile leaf. What’s also noticeable is the colour and texture of the stem itself changing.
The mature foliage. Dark green and on the underside, grey with fine hairs (tomentum). These leafs will produce flower buds. The leaves become leather like and are less photosynthetic than juvenile shoots. They are however more drought and salt tolerant, keep this in the back of your mind when considering environmental conditions pertaining to bonsai vessels and in turn soil requirements etc.

Okay with that illustration in mind, how do I get the tree to produce some or more mature foliage. Well the answer is pretty simple, you have to avoid the stress actions that warrant the tree to want to continue to produce juvenile shoots in favour of mature.

The most common stress inhibitor is pruning. It’s an action that is performed the most frequent and without knowing it, it is probably the main stress inhibitor that is causing your tree not to mature. This is why we commonly see the glossy foliage on our Pōhutukawa bonsai. Now hold onto that for a moment when we consider some thoughts below.

Yes a young tree needs to mature and this can take up to 10 years as per some studies. In this case we are often letting the tree grow and thicken. On a side note, it’s worth noting that the cultivar ‘Māori princess’ seems less likely to revert/ produce juvenile shoots when pruned back heavily.

Some points to ponder as we close up this blog post!

1) Can you develop a Pōhutukawa faster into a bonsai using the vigour of juvenile shoots?

2) Can you then transition this to mature foliage after development without losing that development work?

3) If flowers are not within your desired future composition can you keep your Pōhutukawa in a juvenile state for ever?

These are all things we are exploring in our own garden and with our clients. We have a fascinating example that we are observing and hope to bring you the results early next year.

This tree has been container grown from a seedling and is now +_15 years old, still relatively young! It has been in my collection for a few years now and since its initial styling it has largely been left to its own devices. This spring has seen a dramatic shift to more mature foliage being produced and as a result its first set of flowers. It is growing on a piece of slate in 100% akadama.
Two Islands Bonsai
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