The terrestrial portion of the park lies within what the province terms the Coastal Western Hemlock Biogeoclimatic Zone, based on the climax vegetation, in the very dry maritime subzone (CWHxm1). The air masses coming from the Pacific Ocean loses much of its moisture as it passes the Vancouver Island Ranges, resulting in this area experiencing warm summers with little rain but wet winters. This leads to western hemlock being the potential dominant tree species. However, in second-growth forest the most abundant tree is usually Douglas-fir. Western redcedar and grand fir grow in the drier nutrient-rich sites and red alder and bigleaf maple grow where disturbance has resulted in sun exposure, like along the borders of clearings. In the mature forest areas, shade-tolerant plants grown in the understory, such as red huckleberry, salal, Oregon grape, sword fern, and vanilla-leaf.