Forested seeps are shaded groundwater seepage areas with active spring discharges located within a matrix of upland hardwood forests. They are usually small in size, often only a few acres or less. However, under the right geological conditions such as broad seepage slopes, they can cover much larger areas. Seeps often coalesce into small babbling streamlets but can also occur in smaller pockets at the base of slopes, just above larger wetlands or rivers. They occur in a variety of landscape settings including moraines, river valleys along the margins of sandy outwash plains and lakeplains, and small steep-sided valleys in the Driftless Area. Soils are usually muck to mucky peat over a deeper sandy clay layer.
The canopy is usually dominated by black ash (Fraxinus nigra) and yellow birch (Betula alleghaniensis) with lesser amounts of basswood (Tilia americana). Surrounding uplands are usually dominated by mesic hardwoods such as sugar maple (Acer saccharum), red oak (Quercus rubra), and basswood, which often overhang smaller seeps and can contribute significantly to overall canopy cover. Small trees are usually occasional, especially musclewood (Carpinus caroliniana), American elm (Ulmus americana), mountain maple (Acer spicatum), and alternate-leaved dogwood (Cornus alternifolia).
The groundlayer is often lush and includes groundwater-loving species such as skunk cabbage (Symplocarpus foetidus), marsh marigold (Caltha palustris), golden saxifrage (Chrysosplenium americanum), swamp saxifrage (Micranthes pennsylvanica), and brome-like sedge (Carex bromoides). Sites often also reflect their upland matrix forest and contain mesic forbs such as lady fern (Athyrium filix-femina), wild geranium (Geranium maculatum), miterwort (Mitella diphylla) and zig-zag goldenrod (Solidago flexicaulis) alongside common wetland species such as jewelweed (Impatiens capensis), wood nettle (Laportea canadensis), fowl manna grass (Glyceria striata) and various asters (e.g., Symphyotrichum lateriflorum, S. puniceum).
