Wolf Trap, like many places, is struggling with a number of introduced species of plants that threaten many of the native wildflowers, trees, and shrubs. Japanese honeysuckle (Lonicera japonica) vines are strangling smaller trees in some places, and the low-growing multiflora rose (Rosa multiflora) is crowding out native shrubs. In 1999 the National Park Service developed Exotic Plant Management Teams to locate and control exotic plants, and assist in restoring these sites to their native ecosystems (http://www1.nature.nps.gov/epmt/NCR). The most aggressive invader at Wolf Trap is the lesser celandine plant (Ranunculus ficaria). This small European plant forms clumps of attractive green leaves and yellow flowers along the stream and in wetter areas, blooming early in the spring. Although beautiful, celandine forms thick, impenetrable mats that choke out native wildflowers. The park has begun an aggressive campaign to control lesser celandine. Other exotic species in the park that may need controls in the future are Japanese stiltgrass (Microstegium vimineum), garlic mustard (Alliaria petiolata), Japanese barberry (Berberis thunbergii), and beefsteakplant (Perilla frutesceus).