Eduardo Stehling, Biologist – Bela Vista Forestry.

When it comes to producing wood for timber, regardless of the species planted, it is inevitable that at some point there will be the recommendation to “do the pruning.” Pruning or clearing branches to date is a subject so controversial and enigmatic that, depending on the tone that is used to suggest, it can excite or dishearten farmers. The purpose of this article is to help demystify pruning operations of and help farmers who are interested in producing timber for sawmills.

Pruning needs to be done. What now? And if I do not prune? How much do I cut off? When should I do it? Where do I cut? Do I need to use something? How high? Up to what age? What do I do with the branches? Did I cut too much? These are just some of the questions that plague timber producers, which when combined with the lack of technical knowledge on the management of all existing species; it usually ends up in losses to the beginner forester. As a producer, I started doing this 8 years ago, and went through the same questions regarding Australian cedar, initially working with the seminal material. Today, pruning was greatly simplified with the clones. In order to share what I learned and help form common sense among producers vis-à-vis this operation, we shall start from the basics.

Usually, in timber production for sawmill, the noblest part of the log is used to produce boards. The added value is greater if the timber is free from knots, which are nothing more than parts of dead branches that were assimilated during the plant’s diametric growth. Knots, either decaying or not, detach easily from the board, leaving holes in it. This is mainly due to the dead bark coating the branch that is also assimilated. Knots caused by dead branches are very common in pinewood, used for making crates.

So, to make it clearer, the dead branches cause the knots, and our priority is to take them out, not the living branches. Live branches enlarge the volume of the treetops, directly influencing productivity, and therefore, diameter enlargement below them. With a higher volume of leaves, there will be more photosynthetic area, more plant sweating and more roots. Nutrient transportation will be higher, and wider will be the trunk diameter. It is as simple as that. Almost all tree species produce branches in its architecture and to grow healthy plants, we must accept them as allies and not as our enemies. While the branch is still alive, there is wood being formed where it is inserted.

The truth is that the plant is always improving when it has branches. But then come the mistakes. Misunderstandings, such as “the bud is a thief,” or “this branch is stealing the plant’s power,” often giving live branches a worse status than their dead counterparts. Thus, what is better: to leave the branches, or to take them off? Live branches pose problems for trees only when they influence the shape of the trunk. After all, the plant has to be straight. If the tree furcates or loses shape, warps because one or more branches unbalance the canopy, there will be lower financial returns to produces. In these cases the branches should be removed.

Overall, after a few years doing pruning and following producers, it became clear to me that the obsession with pruning can destroy entire plantations. The greatest fear of the farmers is having timber with knots, thus yielding less value than expected. The second greatest fear is to let the branches develop, because then they would need to remove them when they are bigger and thicker. These unfounded fears can bring about bad consequences. It is very common among farmers to do excessive pruning of plants with diameters less than 5 cm, between 6 and 18 months of age. Trees that are still not ready to produce wood have any budding momentum strangled. It is almost as if the branches were ticks in a cattle herd. When such pruning is done, there is a widespread and destructive loss of force in the crop, because it is between 10 and 16 months that the trees experience major growth spurts. Rain and proper temperatures happen between October and April, and pruning is not recommended at this time.

Often times, the farmers are blankly wondering, “why are the trees not growing, I used a lot of fertilizers.” Without canopy growth, the roots do not grow for proper nutrient absorption and transport, leading to very little growth. Implementation is hampered by interference from the farmer. I have seen cases in which the whole crop died because of obsessive pruning at the 3rd year of the forest.

In future issues I will address other aspects of pruning for sawmills, discussing where to cut the branches and to what height pruning should be carried out. See you then.