Eucheuma spinosum is translucent and has an erect, spherical thallus form. A swelling covering the surface of the thallus resembles irregularly formed sharp spines that are elongated, resembling branches. Lush branches can clump together to support plants. Thallus branching grows erratically in both old and young portions. 5 to 30 cm in length. From yellow-brown to yellow-red.