Saccharina dentigera is a large brown seaweed growing to a length of . The
thallus is dark brown, thick and leathery, often appearing palmate because of being split into broad lobes to within of its base. Younger thalli are entire with ovate blades. The thallus is supported on a robust, semi-rigid
stipe, which has
mucilage ducts on its surface near the upper end. The stipe is attached to a rock surface by a branched
holdfast up to high. Each holdfast only bears one thallus, but new blades sometimes start to grow before the old ones are shed. ==Distribution and habitat==