The GARDENA gardening expert
Dear Mr. D., I would need to know what variety of maple this is exactly. If we are talking about an arboreal maple (e.g. sycamore, Acer pseudoplatanus, or the Norway maple, Acer platanoides), we have to proceed differently than with the plants which grow as shrubs (e.g. the Japanese maple, Acer palmatum, or the Amur maple, Acer ginnala).
However, as orientation I can say the following: the arboreal maples will consistently attempt to achieve their typical growth characteristics even if you try to extend the width rather than the height (for example, by removing the main shoots). Therefore the promotion of wide growth will only be relatively successful. It is easier to control the growth of shrub-type maples, even if they hardly have to be cut back. They always grow more in width than in height through their very nature, and often in an approximate funnel shape, meaning that they are wider at the top than at the bottom. On the other hand, you can achieve extremely good width growth with the field maple, Acer campestre. This may be a small tree, but it initially grows like a large shrub, and, decisively, features strong horizontal branch growth, which allows it to expand in width.
In order to improve the width of your maple, make use of the winter cut (on frost-free days until the end of February at the latest) and the summer cut (beginning of May to the middle of June). During the winter cut, trim the vertically-growing branches. The new shoots will then fork and extend sideways. Trim these new shoots again in summer, making them fork again at the end of June (the so-called Lammas growth). How far should you cut back the shoots? Back to the section of tree from where you would like it to widen. There, where you have cut, is where the wider growth will begin.
You must remain consistent with this “wide” cut, as according to the nature of growth after trimming, the plant will always try to grow more at the tips than at the base of its branches. You will therefore only manage to increase the width of the plant by curbing the horizontal tips through the promotion of forks. – Of course, this guideline depends, as mentioned above, on which variety of maple you actually have in your garden.
Photo: © Oleg Mitiukhin - Fotolia.com