Axes of Hypnea spinella spread through entire length of plant. Main branches are not present. Branching dichotomous in all directions. Axils rounded, sides symmetrically developed, growing nearly horizontally before bending up or curling downward. Color of plants yellowish to light red or pink in colour, sloppy, in tangled, bushy clumps. This curling tendency produces the characteristic tangled branches. Branches thicker below more slender above, tapering abruptly to acute tips. Holdfasts small, unclear, or absent.