Leaves of marah macrocarpa
are bright green, not glaucous like some similar species, divided about half way to the base into five (most common) or seven broad lobes, and crossed by prominent, lighter-colored veins. Leaves and the grooved stems have a sparse covering of short hairs. Each leaf node also bears a branched tendril. This species occurs along the coast of southern California, to around 50 miles inland, from San Diego to beyond Santa Barbara, and it can be locally abundant.
Plants are monoecious; flowers may be pistillate, one per leaf node, or staminate, in a small, elongated cluster, also one per node. Petals are creamy-white, crossed by thin green veins. Stigma and stamens are pale yellow. The fruit is a spiny, egg-shaped capsule, up to 4 inches long; spines are rigid, unhooked, of differing lengths, and sparsely hairy. Fruits are green, maturing to yellow.