Eastern White Pine (Pinus strobus)
Eastern White Pine, a common coniferous tree in our area, can reach heights well over 100 ft. It is easily distinguished from our other native pines by its light green needles borne in clusters (called fascicles) of 5. These flexible needles are 3 to 5 in. long. The resinous, cylindrical cones are 4 to 8 in. long and require 2 yrs to mature. The smooth gray bark of younger trees becomes furrowed with age. Eastern White Pine is widespread in Eastern Canada and the Northeast US, extending down the Appalachians as far as northern Georgia and South Carolina, and is found throughout the upper Midwest and adjacent Canada. In the 17th and 18th centuries, it was heavily logged by the British for ships' masts. The White Pine Trail above the Arboretum Visitors Center formerly ran through a stand of relatively large, mature examples of this species. Disease and wind damage, however, have eliminated many of these magnificent trees.
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Ebony Spleenwort (Asplenium platyneuron)
Ebony Spleenwort and Christmas Fern (Polystichum acrosticoides) are the two most common ferns found along Arboretum hiking trails. The smaller Ebony Spleenwort is less conspicuous than Christmas Fern. Its upright, fertile fronds (leaves) bearing clusters of spores (sori) can be up to
2 ft in height, but more commonly are less than 1 ft long. The sterile fronds are much shorter (only 2-6 in. long). The leaf petiole and rachis (the stalk to which the leaflets are attached) are dark purplish brown to black, which gives rise to the ebony portion of its common name. Spleenwort purportedly refers to the medicinal properties of this and other Asplenium species. The bases of the fertile frond leaflets (pinnae) are ear-shaped and overlap the rachis. The margins of the pinnae are serrate (saw-toothed) to crenate (somewhat rounded). The distribution of Ebony Spleenwort is unusual in its being found throughout the eastern US, in New Mexico, Arizona, and the West
Indies, and also in tropical and subtropical Africa.
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Elms (Ulmus spp.)
Four native species of Elms are found in East Tennessee - American Elm, Winged Elm, Slippery Elm, and Rock Elm. Beginning in the 1930's, Dutch Elm Disease, caused by a fungus, has greatly reduced the populations of these trees. American Elm, once the major shade tree in towns throughout the Midwest and East, has been virtually eliminated by this pathogen. Three species of elm found along Arboretum trails are briefly described below.
Winged Elm (Ulmus alata) is a relatively small tree growing to heights of 40-50 ft. Distinguishing characteristics include relatively small (1˝ - 3˝ inches long), narrow, coarsely toothed leaves and thin, corky ridges along many of its branches - the wings that are the basis for its common name. Winged elm is found along the lower parts of Cemetery Ridge Trail.
Slippery Elm (Ulmus rubra) is fairly common along Old Kerr Hollow Road. The leaves are up to 7 inches long, and their upper surface is rough, feeling like sandpaper. Its common name refers to the fact that its inner bark has a very slippery, mucilaginous sap. If you scratch a leaf petiole and run a
finger along the split, you can feel its slipperiness. Slippery Elm grows to heights of 60-70 ft.
Rock Elm (Ulmus thomasii) is present along the upper portions of Cemetery Ridge Trail and the South Forest Loop Road. Its leaves are relatively smooth in texture and 2-4 in. long. Rock Elm is also called Cork Elm because of the
irregular corky wings that develop on older branches. It can grow to heights of 100 ft. Although present in East Tennessee, Rock Elm is more common in middle Tennessee. In our area, it is typically found on relatively dry, rocky sites.
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