An A1 poster sized print, approx 23c33 inches (594x841 mm). English oak (Quercus robur) acorns. Acorns forming on an English oak tree. This tree is also known as the pedunculate oak. Acorns are the fruit of the oak tree. In this species, they form in groups of 1, 2 or 3 on a long, common stalk. Photographed in late August. . Image supplied by Science Photo Library. Product ID:6305377_73045_0