Pruning (part 2)

Ever wondered why your favourite magnolia, or camellia, stopped growing that particular branch that was expected to flower?

Well, if you had not done anything to your plant, most probably it has decided for you. In this case, it might well be that that part of that particular branch will die in the end. This situation is quite common in many vascular plants and technically it is their way of pruning themselves. That is right, plant also prune themselves.

Except for aesthetic reasons, which drive many people to prune plants, often not having the best results for the plants, they also decide and drive their growth in order to optimise their physiological status. In the same way, in many situations, plants are pruned by people in order to promote growth, improve their health and productivity, in the case of fruit trees for example. In addition, pruning can also be used as a tool to make certain corrections in plant development according to their needs of light, fertilisation and irrigation.

Before starting your ritualistic garden pruning frenzy that I am sure most of your plants wish it would never happen at all, there are some things you should consider. First, as you may have noticed not all plants respond in the same way to being cut. Remember that pruning is always “harmful” to any plant; you are simply cutting parts of a plant’s body. However, it happens naturally and plants are adapted to respond to it. Most often, especially those not so experienced, what people ask is: what is the best time for pruning? Well that always depend on the species rhythm of growth. There are some basic simple rules that one should always have in mind before starting pruning:


, no matter the reason behind it, pruning should always be performed after plants flower, or in the case of conifers (which do not produce flowers as you may know, e.g. pine) after they have produced their female and male cones. Why? Typically, all vascular plants end their extremities with reproductive organs that will lead to fruits. Therefore, if you cut a branch before this cycle happens not only you prevent plants to reproduce but also you hinder their growth seriously for that season. Normally, in many species, flowering and fruiting marks the end of a growing season. Which, for most temperate climate species it is more or less about at the end of summer.

Second, temperate climate species stay dormant part of the year, usually winter time. In many cases, they lose all their leaves. For these species, winter is the best time for pruning them, as they do not grow and are metabolically inactive. Therefore, cutting them will not make them to respond immediately. Also, remember that in temperate climates, from where these species come from, winter is the hardest season with many storms and rough wheatear. So, plants from these climates are used to lose branches. Therefore, cutting them during that time will not be that different from what they are used to.

Third, tropical plants, on the other hand, grow all year round, having in some cases flowering cycles. In these cases, there is no calendar season to prune them as they will respond the same way. However, if you want your plant to flower not so long after being pruned, be sure to prune after a flowering cycle. This way, you guarantee that the plant will have enough time to grow and develop well before starting a new reproduction cycle. As these tropical plants do not stay dormant, they need some time (like any other plant) to recover from the shock of being cut.

Have this in mind. From the metabolic point of view, flowering is a costly business for many plant species. Plants need to build up enough reserves in order to flower and they can only do that by having a strong and healthy vegetative system, i.e. leaves and roots. It often happens that people prune their plants and then they complain that the plant stopped flowering or it does not flower as before. A typical example is lilac that responds very slowly to pruning. Basically, one can say that lilac does not like being pruned. Normally, lilac takes two years to flower again after it has been correctly pruned. On the opposite side, as you may have noticed, roses respond quite well to pruning and even do not mind being cut several times during the year.

Special thanks to Dr Pablo Cabrita (Phd. Plant Physiology)

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