Some northern hardwoods manage to survive amidst the spruce-fir ecosystem, namely yellow birch, American mountain ash, and pin cherry, the latter being especially common in areas damaged by fire. A typical southern spruce-fir understory is home to shrubs such as Catawba rhododendron, thornless blackberry, mountain cranberry, and witch-hobble. The spruce-fir herbaceous layer contains ferns such as the mountain wood fern, northern lady fern, and clubmoss, and over 280 species of mosses. Wildflowers include Canada mayflower, blue-bead lily, and mountain wood-sorrel. The Rugels ragwort is found only in the spruce-fir forest of the Great Smoky Mountains, and is one of eight plant species endemic to the southern Appalachian spruce-fir ecosystem.