Galium murale (L.) All.  

A weak annual with erect or ascending stems up to 25 cm long. Stems four-angled, hairless, though sometimes with downward pointing prickles along the angles. Leaves 2 to 8 mm long, oblong-lanceolate, sometimes obovate, mucronate, in whorls of 4 to 6; with backward pointing prickles along the margins and sometimes on the mid-vein. Flowers in axillary clusters of up to 3; corolla yellowish-white, about 0.5 mm across. Mericarps oblong, with 2 spreading lobes, 1 to 2 mm long, covered with hooked hairs.