Companion species
Pick one plant and see what grows with it: the natives that share its ground in the wild, and the ones that pair with it in a yard because they want the same sun, soil and climate.
In the wild
Sweet Birch (Black Birch) grows in rich moist slopes, the Appalachians, rocky ground and dry uplands
These natives share that ground, so they will look right together and want the same care.
Blue AshFraxinus quadrangulata shares rocky ground, dry uplands and rich moist slopes
Mountain LaurelKalmia latifolia shares dry uplands, the Appalachians and rocky ground
Allegheny ServiceberryAmelanchier laevis shares rich moist slopes and the Appalachians
American Mountain AshSorbus americana shares the Appalachians and rocky ground
Black HuckleberryGaylussacia baccata shares dry uplands and rocky ground
Carolina BuckthornFrangula caroliniana shares rocky ground and dry uplands
Carolina SilverbellHalesia tetraptera shares rich moist slopes and the Appalachians
Common HackberryCeltis occidentalis shares rocky ground and dry uplands
In the yard
Under its canopy
Shrubs and small trees that take the shade a sweet birch (black birch) casts and like the same soil.
How the matches are made
Every species we grow is tagged with the natural communities it lives in: floodplain forests, swamps, stream banks, rich slopes, dry ridges, sandy barrens, rocky ground, old fields, the forest understory, the mountains and the coast. Wild neighbors are the species that share one or more of those tags, with the closest matches first. Yard pairings use the plant's own needs instead: overlapping hardiness zones and soil moisture, and for the shade pairings, a size difference of at least two classes and a smaller plant that tolerates part shade or shade.
Sharing a habitat tag does not mean two plants always grow side by side, and a tag says nothing about how far apart to plant them. Use the planting-site check for the spot itself, and the growth estimator for how much room each one will want in twenty years.