Earlywood is the first part of a annual ring, formed in spring and early summer. It is porous and lighter than the latewood. The transition from earlywood to latewood is in some species more distinct than in others. In Picea it is diffuse but in Pinus distinct enough to make separated measurements for earlywood and latewood ring widths useful. In Quercus and other ring porous species the difference between earlywood and latewood is obvious, but the border not straight.