Spiny emex leaves are triangular to ovate, 3-12 cm long and 2-10 cm wide. They are mostly hairless with undulate margins.
Lower leaves grow on long stalks while others grow on stalks at similar length or shorter than the leaf blades. Each leaf stalk is surrounded by a membranous sheath at the base.
Male and female flowers of spiny emex are separate on the same plant and not conspicuous. Male flowers are in small stalked clusters, while the female flowers are almost sessile (attached directly to its base without a stalk) in the leaf axils.