Catherine Lake Hemlock-Hardwoods features an extensive stand of mature, mesic forest on rolling moraine located on the east side of Catherine Lake. Although the forest varies in quality and composition, the eastern half contains a relict old-growth stand dominated by large hemlock, yellow birch, and sugar maple with the largest trees averaging near 50 inches in diameter. Super-canopy white pine occur near the lake. With some trees estimated at 250+ years in age, it is likely that the least disturbed areas of the SNA were never clear-cut during the cut-over era. These areas contain old-growth characteristics including snags, tip-up mounds, coarse woody debris, and a multi-layered canopy. The groundlayer is diverse and includes species such as red baneberry, maidenhair fern, wild sarsaparilla, American starflower, Canada mayflower, early coral-root, sharp-lobed hepatica, lycopods, naked miterwort, large-leaved shinleaf, and twisted stalk. Wetter areas contain an understory that includes bog rosemary, grass pink, wild calla, pitcher plant, round-leaf sundew, mountain wood-sorrel, bunchberry, three-leaved goldthread, and yellow blue-bead lily. Associated with the extensive uplands forests are five small undeveloped lakes, a complex of wetland communities including open bog, black spruce swamp, emergent marsh, sedge meadow, and alder thicket. The site supports numerous rare plants and animals including black-throated blue warbler, cape may warbler, gray jay, giant rattlesnake plantain, and northern black currant. Catherine Lake Hemlock-Hardwoods is owned by the DNR and was designated a State Natural Area in 2007.