The Best Time for Felling
There are many different opinions about what is the best felling time. An expert in woodworking, Martin Häggman, has made wide-ranging surveys and analyses of wood for decades now. Based on his research, he has come to the following conclusions:
The best felling time depends on the tree species. The best felling time for broadleaved trees such as birch is at the end of summer in August, when the moisture content of the tree is about 43 %. For the sake of comparison, the moisture content in May is 55 %. At the end of summer the moisture content is naturally the lowest.
Another factor favouring autumn as the best felling time is that the leaves have stopped growing, and are no longer absorbing nutrients off the tree. Thus the firewood produced will be of much higher quality. At the end of summer only water escapes through the leaves.
Broadleaved trees should be left lying on the ground unpruned for three weeks. During this time, the leaves absorb water off the tree and the moisture content decreases. After three weeks the moisture content has dropped ten per cent, to 33 %. This felling technique is called leaf-seasoning method.
Immediately in the autumn the birch is sawed, cut, and stacked. It is also important to cover the wood pile as airily as possible with a tin roof. After one year, the moisture content of correctly stored wood is 13 %. This is excellent moisture content for firewood. If the pile is covered with plastic or tarpaulin, the result is considerably worse.
Unlike broadleaved trees, spruce and pine do not need leaf-seasoning method, but should be felled late in autumn or in winter. They should also be cut in winter so that most of the water dries during frost.
By leaving part of the tree tops in the forest many advantages are gained and many disadvantages caused by felling are avoided. Branches and needles are the most nutritious parts of a tree. When they are left in the forest, the growth of a new tree generation is secured, even better than with fertilisation.