Fagaceae (Beech family)
Description: Small to medium-sized deciduous tree with a dense round crown of large, gnarled, horizontal branches. Leaves leathery, shiny dark green above, light green and densely hairy below, 3-5 lobed, the middle pair of lobes largest, suggesting a cross. Male flowers yellow-green, in hanging catkins, female flowers in short spikes in leaf axils, appearing with the leaves. Acorns one-half to 1 in. long, broadest at base, with shallow cups enclosing about one-third of the nut. Flowers Apr.; fruits Sept.-Nov.
Habitat/range: Dry upland woodlands and forests, including dry oak-hickory forests and xeric hardpan forests. Common in piedmont, uncommon in mountains. Widespread in eastern United States.
Taxonomy: The cross-like leaf shape and dense covering of star-shaped hairs on the lower leaf surface characterize this species.
Ecology: Post oak typically grows on dry sites with shallow, nutrient poor soils. On more favorable sites, neighboring trees often overtop it because of its slow growth rate. On poor sites, it tends to persist because it's more drought resistant than most other trees. Individuals can live for 300-400 years. Like many shade-intolerant species, it benefits from periodic fires opening up the canopy. Smaller trees are easily topkilled by fires, but vigorously resprout from dormant buds at the base. Fire scars on surviving trees provide an entry point for fungi that can cause heart rot and eventual tree death. Individuals begin producing acorns after about 25 years. A masting species, good acorn crops are produced every 2-3 years. Acorns ripen and fall from the tree in autumn and germinate shortly thereafter.
Wildlife: In good acorn-producing years, mammals such as squirrels, black bears, and white-tailed deer fatten quickly, and are more likely to produce healthy young the following year. Cavities provide nests and dens for various birds and small mammals.
Uses: Post oak makes a good landscape tree on dry sites but is slow growing and occasionally succumbs to chestnut blight.
Robinia pseudoacacia L.
Fabaceae (Legume family)
Description: Medium-sized, fast-growing but relatively short-lived tree with deeply furrowed bark and stout, paired spines at nodes. Leaves alternate, deciduous, pinnately compound with 7-19 leaflets. White, fragrant, pea-like flowers in drooping clusters. Flat brown pods (legumes) 2-4 in. long often hang from branches through winter. Flowers Apr.-June; fruits July-Nov.
Habitat/range: Forests, woodlands, and disturbed areas, including roadsides, clear cuts, and abandoned fields. Common. Native to central and southern Appalachians from Pennsylvania south to Georgia.
Taxonomy: Robinia is a small genus of 8 species of shrubs and trees native to eastern and southwestern North America, 5 of which occur in the mountains and piedmont.
Ecology: Black locust has been introduced and subsequently naturalized over a wide geographic area, including parts of Canada, Europe, and Asia. Its success reflects an ability to tolerate a wide range of environments, grow rapidly, reproduce at an early age, produce large seed crops, and to spread rapidly by root sprouts, forming clones.
Wildlife: Black locust is susceptible to various insects and pathogens, including the locust leafminer, which causes the leaves to turn gray or brown, suggesting an early fall color change. A more destructive insect is the locust borer, a black, yellow-lined longhorn beetle whose larvae build feeding tunnels throughout the wood. The tunnels provide entry points for heart rot fungi that cause extensive wood decay, sometimes leading to tree death. A sap-sucking insect known as the locust treehopper mimics the thorns of black locust, thus hiding from predators. If a thorn appears to be moving, this insect may be playing hide and seek with you. Because of its susceptibility to insects and rots, black locust is a good nest-cavity tree, particularly for woodpeckers.
Uses: As a nitrogen fixer, black locust can grow on nutrient-poor soils and is often planted on reclamation sites for soil improvement and erosion control. Its wood is used for split rail fence posts, as seen along the Blue Ridge Parkway.
Sassafras albidum (Nutt.) Nees
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