The fracture energy of wood and root burl wood of thuya was measured using a single-edge-notched specimen bending test method. The variations along the longitudinal (L) and transverse (T) directions were studied using specimens taken from one radial (R) section each of thuya wood and thuya burl. Thuya burl was more resistant than thuya wood to crack propagation in RL system (in the tangential plane). This difference is explained by the presence of outgrowths, composed of cells with thicker walls that make the burl wood usually denser than thuya wood which was consistent with the radial orientation of the outgrowths. The decrease of fracture energy along the longitudinal direction was explained by the progressive reduction of outgrowths concentration.