The flora in this ecoregion varies considerably based on soil conditions and elevation. These mixed forests are distinct from the deciduous forests south of the Canadian Shield and the cooler boreal forests to the north.
Conifer swamp
Conifer swamps occur in areas that are seasonally flooded. Trees can be very dense or sparse; mats of sphagnum moss cover the ground. Black spruce and tamarack are the predominant tree species. Where the soil is not saturated year round grows northern white cedar. Speckled alder grows around the edges of these swamps and red spruce and white pine grow on higher, drier ground.
Lowland conifer forests
Lowland conifer forests occur on flats, low ridges, and knolls near bodies of water. They are dominated by balsam fir and red spruce, although white pine and paper birch also occur. The ground is often stony with little vegetation.
Hardwood–conifer mixed forests
s occur in a transition zone between lowland conifer and northern hardwood forests. The ground is less rocky than in the lowland conifer forests and thus supports more vegetation. Trees include red spruce, balsam fir, eastern hemlock, red maple, and yellow birch. The understory vegetation is abundant, with witchhobble, honeysuckle, and striped maple. The herbaceous layer include common wood sorrel, bunchberry, yellow clintonia, ferns, and mosses.
Northern hardwood forests
s occur on the richest, most productive soils. Sugar maple, American beech, and yellow birch are the predominant tree species. In secondary forests, red spruce, white pine, white ash, eastern hemlock, black cherry, and red maple are present. Witchhobble is a common understory shrub. Ferns and clubmosses grow in the herbaceous layer, along with numerous species of spring-flowering forbs.
Upper slope hardwood–conifer mixed forests
Upper slope hardwood–conifer mixed forests are an area of transition between the northern hardwood and the mountain conifer forests. They are similar to hardwood–conifer forests, but with no red maple. Red spruce and eastern hemlock, together with sugar maple, yellow birch, and American beech are the dominant species, with scattered white pine.
Mountain conifer forests
Red spruce and balsam fir are common at lower elevations of the mountain conifer forests. Hardwoods that grow among the conifers include paper birch, yellow birch, and American mountain-ash. With increasing elevation, balsam fir becomes more abundant. Near treeline, black spruce joins balsam fir in the krummholz. Herbaceous plants include wood sorrel, bunchberry, yellow clintonia, and spinulose woodfern. Mosses and lichens cover exposed rocks.
Alpine
Rocks are exposed and covered with lichens and mosses. Low-lying plants more common in the tundra to the north grow here. They include gold-colored deer’s hair, alpine bilberry, lapland rosebay, bearberry willow, mountain sandwort, and alpine holygrass. In the Adirondacks, these communities are limited to on 11 peaks.