A knot in a tree is better known as a defect or blemish that leads to the formation of lumps or holes within a tree trunk. These knots in wood are caused as the tree grows naturally, though there may be certain reasons that determine their appearance. Though it is true that some knots form due to the tree being infected by fungus that is contagious to some other trees on your estate too.
How knots in wood are formed
As a tree grows normally, its trunk increases in width. Soon, the trunk grows much larger than the branches that grow out of it. It’s common to see knots emerging from around the branches of these trees, thickening in size as the tree keeps on growing. With the branches of the tree continuing to grow, they are quickly overtaken by the tree trunk where a solid knot forms and contains live wood. The knot comprises very thick and tough wood, much more than the wood surrounding it and may end up as a big bulge around a branch that spouts from its middle.
Just as there are several kinds of knots, each type of knot is formed differently for different reasons. Some of them are:
Loose knots: A loose knot forms when a branch is injured or dies while still part of the tree. The tree trunk continues to grow larger naturally. These kind of knots are very much like tight knots except that at their core they do not have living wood but dead or rotting wood material. This matter lying at the heart of the knot is loosely structured and easily removable, often causing an empty vacuum to remain like a hole in the tree trunk, amidst sturdy trunk wood.
Epicormic knots: If a tree is pruned very often, knots form easily. In the course of pruning, often several branches are cut, paving the way for sprouts to form, often called epicormic or bole sprouts. These refer to the nodal points where the branches were lopped off. Just as live branches can overgrow, so also do these, though the smaller sprouts evolve into small-sized knots. When several knots appear in an area of the tree that’s pruned, it is due to several epicormic sprouts that rear their heads post-pruning.
Black Knot Disease: When a fungal disease known as Black Knot Disease infects a tree, it causes the formation of knots in some trees. This disease is characterized by its long, dark knots that can be seen in the woody areas of trees infected by Black Knot Disease. These can be seen on twigs and the smaller branches of trees, and seldom on main branches and trunks when infection is severe. Black Knot Disease is contagious if not treated in time or at all, since fungal spores flit from infected trees to any others that are uninfected by being transported by the wind.
How to prevent the appearance of knots in trees
By pruning your trees regularly, you can prevent the growth of knots. Cutting off low tree branches and growing shoots can help get rid of possible knots. When branches are badly damaged or dying, removing them quickly prevents the formation of loose knots.