Galium Aparine

Medium to tall, brittle, scrambling, bristly plant with square stems with hook like, bristly hairs.  Leaves in whorls of 6 to 9, narrowly elliptical, broadest above the middle, pointed and with bristly margins.  Flowers white, 1.5 to 1.7 mm, stalked, at the base of the upper leaves. 

Courtesy of Naturespot - www.naturespot.org.uk