In the winter when deciduous hardwood trees are barren and dormant, evergreens really stand out. In the cool, damp hollows of the Hocking Hills region of southeast Ohio, one particular evergreen tree is abundant. The eastern hemlock (Tsuga canadensis, Pinaceae) dominates the winter landscape of creeks, waterfalls, and weathered sandstone. The moist, well-drained, and acidic soil here provides the ideal substrate for their growth.
Eastern hemlocks can live to be hundreds of years of age, but the existing trees are much younger. The older specimens were heavily harvested in this area upon human settlement. The bark, rich in tannins, was valuable for the leather industry. The needles, rich in vitamin C, were consumed in tea to prevent scurvy. The timber itself isn’t of much use as lumber since it’s brittle, but it was once used when necessary. Without a modern need for the tannins or vitamin C, hemlocks have regained their status as a dominant canopy tree in this region.
These trees can grow to over 100 feet in height, with trunks up to five feet in diameter in older specimens. They tend to have a tight, vertical growth habit within forests, but spread a bit more in the open. The short (less than 1″), flat leaves are distichous, meaning they tend to grow in two rows on opposite sides of the stem.
The leaves appear glossy and waxy, and the undersides (not shown) have two distinct light bands that are useful for identification. These bands are concentrations of stomata, openings that allow for the respiratory exchange of carbon dioxide and oxygen with the atmosphere.
It was a real treat to hike among the rich, green canopies of hemlocks in the winter. My area in southeast Michigan is dominated by deciduous hardwoods, so the winter canopy is relatively empty. Short of traveling to subtropical climates, northern coniferous forests like this are a great way to see winter greenery.