When trees grow taller, the lower branches will often die due to their location being obscured from the sun. However, since these branches are typically large and strong, they will not fall off immediately, and the tree will continue to grow around the area. This is what forms the conical shape of a knot. Old branches that have died or buds that have not blossomed will produce dead spots in the wood that alter the contour of the following seasonal growth layers. Knots have a harder texture because their grain runs perpendicular to the rest of the tree and the wood has been compressed in that area.