The present invention relates to a blade comprising: a structure of aerodynamic profile comprising two mutually opposite skins; and a spar comprising a fibrous reinforcement obtained by three-dimensional weaving and densified by the matrix, the spar comprising a blade root portion extending outside the structure of aerodynamic profile and an airfoil portion arranged inside the structure of aerodynamic profile between the two skins. Moreover, within the blade root portion, the fibrous reinforcement of the spar comprises a non-debound region and at least two debound regions extending radially from the non-debound region so as to form at least four separate branches.