Native Plants for Pennsylvania

Central Pennsylvania is classic ridge and valley: long parallel ridges of hard sandstone with broad valleys of softer limestone between them, the eroded roots of an ancient mountain range. The pattern is legible on any map and it matters enormously to plants.

Valley floors on limestone have near-neutral soils, deeper and richer, and support a calcium-loving flora. The ridges above them are acidic, thin, rocky, and dry, carrying oak and heath, mountain laurel, blueberry, and the plants that tolerate lean ground. A gardener at the foot of a ridge and one at the top are working in different chemistry.

West of that, the Allegheny Plateau is dissected, cooler, and more uniformly acidic. The southeastern corner runs down into Piedmont, and the far southeast touches the coastal plain near Philadelphia.

What the limestone valleys grow

Where the soil is sweet, the flora is unusually rich. These valleys hold species that will not persist on acidic ground, and the plants are worth seeking out specifically because most regional native plant lists skew acidic by default.

Test your pH before ordering. It is inexpensive, it takes one afternoon, and in this state it changes the answer more than in most.

Deer and the forest understory

Pennsylvania's deer population has reshaped the state's woodlands over decades, and in much of the state the forest understory is missing whole layers that should be there. For a gardener this is the practical daily constraint: a new planting of palatable species will be found and grazed.

The workable approach is to plant mostly low-preference species, which the aromatic and fuzzy-leaved natives supply in quantity, and to protect anything else for its first two or three seasons while it establishes. Ferns, sedges, mountain mint, wild bergamot, and the grasses come through browsing pressure better than most.

Fencing a small area properly beats treating a large area repeatedly.

Planting through the state's range

Southeastern Pennsylvania has a long, warm season and fall planting is comfortably the better choice. The northern tier and the higher plateau are considerably colder and shorter, and spring planting is safer there.

Mountain laurel, the state flower, is genuinely at home on the acidic ridges and struggles in limestone valleys, which is a useful reminder that state symbols are not statewide instructions.

Confirming what is native to your county

The Pennsylvania Natural Heritage Program documents natural communities and species distribution, and the state's Department of Conservation and Natural Resources publishes native plant lists organized by region and site conditions. The Pennsylvania Native Plant Society runs chapters and plant sales, and Penn State Extension provides county-level guidance.

Sources: Pennsylvania Department of Conservation and Natural Resources (native plant lists and natural communities); Pennsylvania Natural Heritage Program (species distribution); USDA PLANTS Database (native status by state).