The strongest branches are typically found in the Douglas fir, Balsam fir, and White pine. These trees have thick branches that can hold a lot of weight and are resistant to breakage. However, it's important to note that the strength of the branches can also depend on the size of the tree and the climate in which it's grown. For example, a small tree grown in a harsh, windy environment might not have as strong branches as a larger tree grown in a sheltered area.