Cactus Rock or Poppy's Rock is a Precambrian granitic rock outcrop, sculptured by glaciers that harbors an unusual assemblage of plant species just south of New London.It is owned by Lawrence University, and was designated a Wisconsin State Natural Area in 1996. It is sometimes referred to as Cactus Rock, due to the presence of a type of wild cactus, Opuntia fragilis.
The rock contains several features created by the scouring of rocks and ice including chattermarks, striations, crescentric gouges, and surface glazing. Vegetation is varied and changes with exposure, inclination, and humus accumulation. Bare rock supports a diverse assemblage of lichens, spikemoss, and mosses. Crevices with accumulated humus harbor many plants with prairie affinities including big and little blue-stem, prairie coreopsis, white wild indigo, bird's-foot violet, prairie alumroot, and lead-plant. Larger areas of accumulated humus harbor trees. On the upper slopes are red cedar, black oak, and jack and white pines. The north slope is dominated by red maple, big-tooth aspen, and quaking aspen. Shagbark hickory, red maple, and black and white oaks dominate the lower south slope and the base of the outcrop. At the western end is a small area of white pine. Common animals include woodchuck, raccoon, opossum, porcupine, and red fox. The site has a history of incompatible human use that has resulted in vandalism, litter, and plant theft.