A blade for a rotor of a wind turbine having a substantially horizontal rotor shaft, said rotor comprising a hub, from which the blade extends substantially in a radial direction when mounted to the hub, the blade having a longitudinal direction (r) with a tip end and a root end and a transverse direction, the blade further comprising: - a profiled contour (40, 42, 50) including a pressure side and a suction side, as well as a leading edge and a trailing edge with a chord having a chord length extending there between, the profiled contour, when being impacted by an incident airflow, generating a lift, wherein the profiled contour is divided into: - a root region having a substantially circular or elliptical profile closest to the hub, - an airfoil region having a lift-generating profile furthest away from the hub, and - a transition region between the root region and the airfoil region, the transition region having a profile gradually changing in the radial direction from the circular or elliptical profile of the root region to the lift-generating profile of the airfoil region, and wherein - the blade is provided with a flow guiding device added to the profiled contour (40, 42, 50) of the blade on the pressure side of the blade, the flow guiding device having an inflow surface with a start point oriented towards the leading edge of the blade and an end point oriented towards the trailing edge of the blade, the distance between the inflow surface and the profiled contour (40, 42, 50) increasing from the start point to the end point, wherein - the flow guiding device extends along at least a longitudinal part of the transition region and is arranged so as to generate a separation of airflow along at least a central longitudinal portion of the flow guiding device from the pressure side of the blade at a point between the flow guiding device and the trailing edge of the blade, when the blade is impacted by the incident airflow, and wherein the inflow surface is concave, characterised in that - the inflow surface in at least the central longitudinal portion is formed so that, for each transverse cross-section, an end point tangent to the inflow surface at the end point crosses the profiled contour (40, 42, 50) at a crossing point, where the profiled contour (40, 42, 50) has a profile tangent to the profiled contour (40, 42, 50), and wherein an acute angle (a) between the profile tangent and the end point tangent is at least 45 degrees. - a profiled contour (40, 42, 50) including a pressure side and a suction side, as well as a leading edge and a trailing edge with a chord having a chord length extending there between, the profiled contour, when being impacted by an incident airflow, generating a lift, wherein the profiled contour is divided into: - a root region having a substantially circular or elliptical profile closest to the hub, - an airfoil region having a lift-generating profile furthest away from the hub, and - a transition region between the root region and the airfoil region, the transition region having a profile gradually changing in the radial direction from the circular or elliptical profile of the root region to the lift-generating profile of the airfoil region, and wherein - the blade is provided with a flow guiding device added to the profiled contour (40, 42, 50) of the blade on the pressure side of the blade, the flow guiding device having an inflow surface with a start point oriented towards the leading edge of the blade and an end point oriented towards the trailing edge of the blade, the distance between the inflow surface and the profiled contour (40, 42, 50) increasing from the start point to the end point, wherein - the flow guiding device extends along at least a longitudinal part of the transition region and is arranged so as to generate a separation of airflow along at least a central longitudinal portion of the flow guiding device from the pressure side of the blade at a point between the flow guiding device and the trailing edge of the blade, when the blade is impacted by the incident airflow, and wherein the inflow surface is concave, characterised in that - the inflow surface in at least the central longitudinal portion is formed so that, for each transverse cross-section, an end point tangent to the inflow surface at the end point crosses the profiled contour (40, 42, 50) at a crossing point, where the profiled contour (40, 42, 50) has a profile tangent to the profiled contour (40, 42, 50), and wherein an acute angle (a) between the profile tangent and the end point tangent is at least 45 degrees.