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Sassafras (Sassafras albidum)

Sassafras Leaves Sassafras Blossoms Sassafras Fall Leaves

Sassafras, a tree frequently seen along Arboretum trails, has distinctive leaves varying from a common 3-lobed shape, to a mitten shape, to an elliptical or oval unlobed leaf. Its small greenish-yellow flowers come out in early April before the leaves. In October, the orange, red, to almost pink leaves contribute to a brilliant display of fall colors. The dark blue fruits (drupes) can be seen in September before they are quickly consumed by birds. Sassafras is widely distributed in the Eastern and Midwestern US, ranging south from southern Maine and Michigan (and southern Ontario), and west to Iowa, Illinois, Missouri, Kansas, Oklahoma, and Texas. It can grow to heights of 60-70 ft. In the Arboretum forests, it is most commonly a member of the understory and lower canopy where it is often found growing in clonal clumps. It is an early invader of disturbed areas and can often be seen along forest edges.

Sassafras has been used for a variety of medicinal purposes. The roots and bark have been used for making Sassafras tea and root beer flavoring, and ground-up leaves are used to make Filè powder, a food thickening agent used in Cajun cooking. Safrole, a carcinogenic component of sassafras oil, has been banned for use as a flavoring by the US Food and Drug Administration.

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Sawtooth Oak (Quercus acutissima)

Sawtooth Oak Leaves Sawtooth Oak Acorns Sawtooth Oak Bark

Sawtooth Oak is a native tree of Japan, Korea, China, and the Himalayas that has been widely planted in the U.S. as a shade tree. It is considered a good tree for wildlife because it produces large crops of acorns, but it has also been identified as being a potentially invasive species in some areas.

Sawtooth Oak grows quickly, reaching heights of 40 to 50 feet. Its distinctive dark green leaves are oblong to lance-shaped and have bristle-tipped teeth along the leaf margin. The dark brown, oval shaped acorns are covered by a cap with spreading reflexed scales resembling hair. The gray-brown bark is ridged and deeply furrowed.

Several Sawtooth Oaks are found in an oak collection area along Arboretum Drive, and one labeled tree is located at the end of Marsh Road near its junction with the Forest Loop Road.

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Scarlet Oak
(Quercus coccinea)

Scarlet Oak Trunk Scarlet Oak Fall Leaf Scarlet Oak
At the end of October, the peak of fall colors is waning, and leaves are accumulating on the forest floor. The leaves of Scarlet Oak, one of the most colorful contributors to this fall display, turn bright red before falling. You can see this tree along our Arboretum trails. It is a member of the red oak group, with its sharply lobed, bristle-tipped leaves and deep, C-shaped sinuses extending close to the mid-vein - features distinguishing it from northern red oak and black oak. The swollen bases of many older trunks is caused by the same fungus that causes chestnut blight. Scarlet Oak ranges from New England, south along the Appalachians and Piedmont to Alabama and Georgia, and west to Michigan, Illinois, Missouri and Mississippi. The wood is used as lumber, flooring, and furniture. Its acorns are favorite food for deer, small mammals, and birds.

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Seaside Alder (Alnus maritima)

Seaside Alder Shrub Seaside Alder, a tall shrub found along Scarborough Creek below the Arboretum Visitors Center, is native to four counties on the Delmarva Peninsula of Maryland and Delaware, but is also found in south-central Oklahoma and northwestern Georgia. This unusual distribution is not well understood, but temperature and moisture regimes of the regions are somewhat similar. Recent studies suggest that these three distinct populations may be remnants of a former much larger distribution. Seaside Alder may reach heights of up to 20 meters. It has toothed elliptical to ovate leaves that are dark green above and pale green underneath. It is found on damp and wet soils in wetland habitats along streams, rivers and edges of ponds. This alder species has been used in the Philippines in efforts to reforest eroded lands. It has also been used for a variety of folk remedies and for dyes, insect repellants, insecticides, and possible emergency food.

Seaside Alder Male Catkin Seaside Alder Female Catkin Seaside Alder develops male catkins in the fall (male catkins have been observed in late August on our specimens). The small pistillate catkins develop near leaf bases. In their native habitat these flowers develop in the fall, while our plants develop the flowers in February and March. Seaside Alder has root nodules with symbiotic nitrogen-fixing bacteria, which convert inorganic nitrogen from the atmosphere to a form that can be used by plants.

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Shingle Oak (Quercus imbricaria)

Shingle Oak As its name reflects, Shingle Oak has a long history of use for making shingles. Early French colonists in Illinois found that the wood could be split into thin sheets and was also resistant to decay. The distribution of Shingle Oak is centered in the Midwest extending south to Tennessee and Arkansas and east to Pennsylvania and Maryland. In Tennessee, it is most common in the central portions of the state.

Shingle Oak Leaves The oblong to lance-shaped, dark green leaves have a short bristle tip. Three Shingle Oaks are present in the Oak Collection near the Arboretum's Program Shelter. They are readily recognized at this time of year because the dark green leaves have yet to change color. As is true for other members of the Red Oak group, the small brown acorns require two years to mature .

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Shortleaf Pine (Pinus echinata)

Short Leaf Pine The area currently occupied by the Arboretum was mainly farmland when the government took it over in the early 1940s. Shortleaf Pine and Virginia Pine (P. virginiana) were two of the trees that first invaded the abandoned farmlands. These pines grow in the open, where competition from other trees for light, moisture, and nutrients is limited. As the forest developed, deciduous species such as oaks, hickories, and tulip poplar, gradually became established and have become the dominant trees. Recent research at the UT Forest Resources Center in Oak Ridge and the Chuck Swan State Forest near Norris evaluated the historical development, current conditions, and future potential of the Shortleaf Pine resource and found that this species flourished in the past as a result of repeated disturbance from fire, logging, and clearing for farmland and other developments. However, these types of disturbances and associated reforestation patterns have been virtually eliminated in much of our region, so that little Shortleaf Pine regeneration occurs today. Although some older individual Shortleaf and Virginia pines are still present at the Arboretum, these trees are gradually dying out. Southern pine beetle infestations in recent years have hastened the demise of these pines, and remnants of their trunks are scattered through-out the forest floor.

Shortleaf Pine Bark Shortleaf Pine Cones and Needles Shortleaf pine can be recognized by its platy bark, straight needles (3-5 in. long) borne in fascicles (bundles) of 2-3 and a flat-topped crown. The seed cones, which mature in 2 years, are ovoid to conic in shape with stout, sharp prickles on the umbo (a knobbed protuberance on the cone scales). Shortleaf Pine is an important timber tree in the South-east, with its wood used for lumber, plywood, boxes and crates, and pulpwood.

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Silverbell (Halesia tetraptera)

Silverbell Blossoms Silverbell can be seen in several locations at the Arboretum just below the Visitors Center near Scarborough Creek, along the lower Heath Cove Trail, and near the Program Shelter. It is a tree that is most typical of the southeastern mountains, but forms can be found throughout the southeastern and central U.S. Silverbell is in bloom this week and is readily recognized by its showy white, bell-shaped flowers hanging down from the branches. In late summer and fall, the green to brown, papery, 4-winged fruit has a long spike-like projection at its bottom.

A research collection near the Program Shelter was established in 1997 to evaluate ornamental characteristics, hardiness, and growth rate of trees obtained from 4 geographical areas in Tennessee, North Carolina, Arkansas, and West Virginia. Silverbells wood is valued for making furniture and wood carvings. Several cultivars have been developed for landscaping.

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Winged Sumac and Smooth Sumac
(Rhus copallinum and Rhus glabra)

Winged Sumac Flower Winged Sumac Berries Winged Sumac Fall Leaves

Winged Sumac (R. copallinum) is one of two common species of sumac found in our area. It has large pinnately compound leaves with petioles that have "wings" - flattened blade-like structures - running along the leaf stalk between the leaflets. The flowers appear in June, and the dull red to purple fruits are well-developed by September. The leaves turn bright red in the fall.

Smooth Sumac Red Flowers Smooth Sumac Flower Smooth Sumac Bark

Smooth sumac (R. glabra) differs from Winged Sumac in having toothed leaflets and no wings along the leaf axis. The bark of Smooth Sumac has distinct lenticels but lacks dense pubescence that is characteristic of other species of Sumac. The fruits of both these species provide a food source for many birds and small mammals. Other members of this genus include Staghorn Sumac (R. typhina) and Fragrant Sumac (R. aromatica).

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Sourwood (Oxydendrum arboreum)


Sourwood is a small to medium-sized tree found along many Arboretum trails. It ranges from Pennsylvania, Ohio, and Indiana, south to northwest Florida, Alabama, Mississippi, and Louisiana. As a member of the Heath Family (Ericaceae), it is related to such plants as blueberries, rhododendrons, and azaleas. The white, bell-shaped flowers are borne in terminal one-sided clusters and appear in late June and July. The fruits mature in late summer and persist on the flower stalks, often into fall and winter. Because the flowers are often near the top of the trees, they may be difficult to see under a forest canopy. The finely toothed leaves, 5-8 in. long, turn a yellow to crimson red in the fall. A good place to observe these trees in bloom is a Sourwood study plot just below the Arboretum’s Elmore Holly Collection.

The ridged and often deeply furrowed bark of Sourwood is readily identified especially in older trees where it becomes distinctly blocky. Trees may grow 50-60 ft high, with trunks that are often bent or leaning. The common name comes from the sour taste of the leaves and twigs. Leaves and bark of Sourwood were used by Native Americans and early settlers to treat a variety of ailments such as mouth ulcers, asthma, indigestion, and kidney and bladder ailments. Sourwood has little timber value, but the heavy wood has been used for handles, fuel wood, and specialty items. Sourwood honey is a favorite of many.

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Southern Adder's Tongue Fern (Ophioglossum vulgatum) and
Rattlesnake Fern (Botrychium virginianum)

Two ferns belonging to the plant family Ophioglossaceae can be seen along some of the Arboretum trails in late April and early May. This group of ferns is considered to have primitive characteristics and is not closely allied to other living ferns. Plants in this family have two-parted leaves, a basal sterile portion that can be simple or compound and an upper fertile portion bearing sporangia.

Southern Adder's Tongue Fern The Southern Adder's Tongue Fern is an unusual fern with a simple, ovate leaf subtending an erect, fertile stalk which bears the sporangia. This fern is widely distributed in the U.S. (many eastern states, Texas and Oklahoma), but is also found in Mexico and Europe. It is often difficult to find and frequently occurs in disturbed areas such as the edges of fields and forested roadsides.

Rattlesnake Fern The leaves of Rattlesnake Fern consist of a basal three-parted compound leaf subtending a fertile spike bearing sporangia. The fertile portion resembles the rattles of a rattlesnake. This fern is found throughout the U.S. and Canada. where it typically occurs in rich, moist forests.

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Southern Red Oak (Quercus falcata)

Sassafras Leaves Southern Red Oak is one of several red oak species at the Arboretum. The red oaks have sharply lobed leaves that are bristle-tipped and their acorns require 2 years to mature. Other common native red oaks occurring here include Black Oak (Q. velutina), Scarlet Oak (Q. coccinea), Northern Red Oak (Q. rubra), and Blackjack Oak (Q. marilandica). Red oaks differ from white oaks that have rounded leaf lobes or teeth without bristle tips and acorns that require only 1 year to mature. Southern Red Oak has distinctive alternate leaves which are shiny on the upper surface and rusty colored pubescent on the underside. Leaves on mature trees are deeply divided with long, sharply pointed lobed tips and 2-4 curved side lobes that are bristle-tipped. The leaf base tends to be rounded and resembles a turkey foot. Young trees may have bell-shaped leaves with 3-5 rounded bristle-tipped lobes. These leaves often resemble those of Blackjack Oak.

Southern Red Oak Acorn Southern Red Oak Bark The acorns are orange-brown at maturity and their caps cover 1/3 or less of the nut. The acorns are important food for wildlife, and the wood is used as lumber for many purposes. The dark bark has scaly ridges separated by deep narrow furrows. A closely related species, Cherrybark Oak (Q. pagoda) has been considered a variety of Southern Red Oak, but it is now recognized as a separate species. It is typically found along coastal plains in the Eastern U.S., while Southern Red Oak occurs on drier upland sites throughout the Southeast.

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Spicebush (Lindera benzoin)

Spicebush Spicebush is an early blooming shrub that is found on the banks of Scarboro Creek below the Visitors Center and along several of the Arboretums trails. It also blooms in the wildflower garden at the Visitors Center during March. Spicebush is dioecious (i.e., it bears male and female flowers on separate plants). When in bloom, the shrub is covered with many small yellow-greenish flowers that appear before the leaves.

Spicebush Berries Three of the Spicebush plants found in the wildflower garden have pistillate flowers while the one close to the bridge entering the Marsh area is male. The crushed leaves and twigs are aromatic, which is the basis for its common name. In the fall, the shrub bears bright red, oblong fruits which persist into the winter and provide a food source for birds.

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Squawroot (Conopholis americana)

Squawroot Inflorescence

In early May, you may see small groups of erect, yellow-brown plants poking through the leaf litter along the Oak-Hickory Trail, the White Pine Trail, and elsewhere on the Arboretum. These pine cone-shaped structures are the inflorescences of Squawroot (also known as Cancerroot). This parasitic plant, which has no chlorophyll, belongs to the Broomrape plant family. The below-ground portion of the plant is primarily a root with a tip, called a haustorium, that penetrates the roots of oaks and absorbs water, nutrients, and sugars from the host trees.

Squawroot Flowers The yellowish-white flowers are borne along the length of the inflorescence and have a light-colored calyx; a tubular, 2-lipped corolla; 4 stamens; and a superior ovary with 2 stigma. The leaves are reduced to brown scales. Each flower produces many very small seeds. Deer, bear, and other mammals may eat these plants and facilitate seed dispersal. The common name apparently refers to its use by Native Americans for medicinal purposes.

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Sweetgum (Liquidambar styraciflua)

Sweetgum Leaves Sweetgum Leaves Sweetgum is a deciduous tree that holds onto its leaves into late November/early December. In late fall one can still find occasional trees with a few yellow to purple leaves along with conspicuous stalked, spiny fruits hanging from the branches. At the Arboretum, Sweetgum can be found along many of our trails. Two large Sweetgums, planted in 1965, can be seen in the Marsh Area.

Sweetgum is found throughout the Eastern U.S. The fruits consist of seed pods united into dense spiny balls. The bark is deeply furrowed into narrow ridges, and the twigs often develop corky ridges along their length. The lobed leaves, which resemble maple, are pungent when crushed.

The gum from which Sweetgum derives its common name has been used historically for incense, perfumery and medicinal purposes. Its lumber has a variety of uses such as furniture, crates, cabinets, and barrels. Its distinctive heartwood is often referred to as “red gum” lumber. The species is widely utilized in the manufacture of engineered composite wood panels and market pulp. It is also an important shade tree.

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Sweetgum Flowers (Liquidambar styraciflua)

Sweetgum Male Flowers Sweetgum Female Flowers As you walk the Arboretum trails in early April, especially along the Old Kerr Hollow Road, you are likely to encounter large numbers of brown, spiky Sweetgum fruits (brown, ball-shaped "gumballs") on the ground. These fruits are shed as the flowers develop in the spring. If you encounter a low branch, you may see upright clusters of male flowers, usually subtended by a single long stalk with a cluster of female flowers. The stigmas of the female (pistillate) flowers cover the surface of the cluster. The male (staminate) flowers develop as a number of spherical heads (approximately 12 or more) along an upright axis. After pollination, the male clusters fall to the ground, and the tightly compact cluster of pistillate flowers develops into a spiky multiple fruit containing about 60 seed capsules. The light weight seeds are dispersed by wind, and the empty brown heads may remain on the tree throughout the winter. Birds and small mammals eat the seeds. Sweetgum is found in much of the Eastern U.S. south of New England, as well as south into Mexico and Central America. Additional information on Sweetgum is provided on our December Featured Plants web page.

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Sycamore(Plantanus occidentalis)

Sycamore Tree Sycamore is a massive tree, growing 80 to100 ft high with wide-spreading branch and root systems. It is found throughout the Eastern U.S., often in bottomland forests, but occupies a variety of upland habitats as well. Sycamores are found in many places throughout the Arboretum, but are especially abundant along Scarborough Creek Road and the Marsh Area.

Sycamore Tree in Fall Season As winter approaches and leaf fall occurs, Sycamores stand out in the forest with starkly white upper trunks. The trees are often referred to as skeleton or ghost trees. The outer bark on lower portions of mature trees breaks into pieces leaving a patchy mosaic of brown, green, and gray overlying the inner white bark.

Sycamore Tree in Fall Season Other key characteristics include large (4-8 in. wide), coarsely toothed leaves that are 3-5 pointed and a ball-shaped fruit on the end of a long stalk that matures in the fall and often persists into the winter.

Sycamore Fruit Sycamore is a fast-growing tree that makes it an attractive candidate for biomass production and as a shade tree. The hard, strong wood has a twisted grain and is difficult to split. It is used for such purposes as pulpwood, particle board, and furniture. Native Americans used Sycamore for a variety of medicinal purposes and the hollowed out trunks for dugout canoes. The leaves, pollen, and fruits of Sycamore are allergenic. The London Planetree, a common street tree in many countries, is a cross between our native Sycamore (P. occidentalis) and the Oriental Planetree (P. orientalis).

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University of Tennessee - Forest Resources AgResearch and Education Center
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