This correspondence presents a simple algorithm to detect and label homogeneous areas in an image, using directed trees for region labeling. The scheme constructs directed trees with the image points as nodes, guided by an edge value computed at every point. These directed trees segment the image into disjoint regions. Because of a valley seeldng property of the tree construction procedure, the boundaries separating the resultant segments pass through the center of the edges. The algorithm thus performs wel1 with thick and wide edges of varying height, because no thresholding of the edge image is involved. The properties of the resultant segments are stated in terms of the edge image. The algorithm is shown to be simple, efficient, and effective for detecting homogeneous segments in the presence of noise. Results of application in the algorithm to segment a LANDSAT multispectral scene of an agricultural area are included.