 The most characteristic trees of southern and low altitude New England swamps are hemlock ("Tsuga canadensis"), northern white cedar ("Thuja occidentalis"), tamarack ("Larix laricina"), balsam poplar ("Populus balsamifera"), red maple ("Acer rubrum"), atlantic white cedar ("Chamaecyparis thyoides"), tupelo ("Nyssa sylvatica") and black ash ("Fraxinus nigra").Often cool, moist shaded ravines are dominated by pure stands of hemlocks in this range.In northern and high altitude swamps of New England the dominant canopy species change to tamarack, black spruce ("Picea mariana") and balsam fir ("Abies balsamea").