University of Tennessee Forest Resources Research Center

Mountain Laurel is an evergreen shrub that may attain the size of a small tree. The showy clusters of flowers are normally pink, but fade to white. A beautiful example of Mountain Laurel can be seen near the Arboretum entrance just below Old Kerr Hollow Road.

Mountain Laurel is found in a variety of habitats in the Eastern U.S., ranging from high-altitude heath balds to dry and rocky forests to floodplains. Other common names for Mountain Laurel include "Sheepsbane" and "Poison Laurel", reflecting the highly poisonous nature of all parts of the plant. It has also been called "Spoonwood" because Native Americans used the roots to make spoons and other small eating utensils. Numerous cultivars have been developed for horticultural uses.

Oxeye Daisy (Leucanthemum vulgare)

Populations of Oxeye Daisy are conspicuous near the upper end of Old Kerr Hollow Road, along Arboretum Drive, and along other trails at the Arboretum in early summer. The showy white flower with a bright yellow center was introduced from Europe in the 1800s and has spread throughout much of North America. Oxeye Daisy produces abundant seed, which remains viable for up to 6 years. It also spreads by vigorous vegetative reproduction of its root system. This invasive plant is listed as a noxious weed in at least five western states and in Ohio. The Tennessee Exotic Pest Plant Council lists Oxeye Daisy as a Rank 3 species (exotic plant species that spread in or near disturbed areas and are not considered a threat to native plant communities.)

Oxeye Daisy is typically found in fields, waste places and other disturbed sites, as well as in the partial shade of open-canopy forests and along forest edges. The individual flower heads, which may be up to 2 inches in diameter, consist of sterile white ray flowers surrounding the yellow disk flowers in the center. Oxeye Daisy has been used for a variety of medicinal purposes and for making wines and tonics.

Cumberland Azalea (Rhododendron cumberlandense)

A showy example of Cumberland Azalea is in full bloom near the Visitors Center this week. The two plants here were transplanted from the Cumberland Plateau several years ago.

Cumberland Azalea is similar to the Flame Azalea (Rhododendron calendulaceum) found at higher elevations in the Smokies and along the Blue Ridge Parkway. These two species along with other azaleas form hybrid swarms on Gregory Bald in the Smokies. The orange to red flowers of Cumberland Azalea are smaller than those of Flame Azalea and appear after the leaves are fully expanded. This species is found in Kentucky, Tennessee, North Carolina, and Northern Georgia and Alabama.

Red Mulberry (Morus rubra)

Early to Late June

Red Mulberry is usually a small tree that can be found along several Arboretum trails Old Kerr Hollow Road, the Cemetery Ridge Trail, and the Backwoods Trail. A large Red Mulberry tree is present just below the Superintendents House along the Valley Road.

Red Mulberry is widespread in the Eastern U.S., but it is disappearing in parts of New England and Michigan, possibly due to bacterial disease. It occurs as scattered individuals in a variety of moist forest habitats and along fence rows and roads. In June you can find Red Mulberry fruits ripening. When mature, the black fruits resemble elongated blackberries and are favorite foods for many birds and small mammals such as squirrels, opossums, and raccoons. The juicy fruits have been used for jams, pies, and wines. The decay-resistant wood has been used for fence posts, furniture, and farm implements. Native Americans used the bark to make fibrous cloth. They also used the plant to treat dysentery and as a laxative or purgative. Un-ripened fruits and the milky sap are poisonous.

Southern Magnolia (Magnolia grandiflora)

By mid-June, Southern Magnolia is in full bloom, although flowers may be seen as early as late April or early May. Some flowers continue to appear throughout the summer. This evergreen tree, native to the southeastern Atlantic coastal plain from southern North Carolina to central Florida and west along the Gulf Coast to Texas, has been planted extensively throughout the Southeast and has escaped into surrounding urban woodlands. Its large (5-8 in. long), elliptic leaves are shiny dark green above, with a velvet rusty surface underneath. When shed in the spring and early summer, the dry, leathery leaves decay very slowly and have been found to be alleopathic (releasing chemicals that inhibit the growth of other plants).

The large, fragrant, creamy white flowers (up to 12 in. diameter), borne at the tips of branches, have many pistils and stamens in a central column, surrounded by undifferentiated sepals and petals (tepals). The flowers are pollinated by beetles. In late summer the erect pinkish fruits mature and, over the winter and the following spring, shed their scarlet seeds. Southern Magnolia typically grows to heights of 50-80 ft with a columnar to rounded shape. The tallest trees reported are over 100 ft high. Several cultivars of Southern Magnolia can be seen near the Visitors Center.

Broad Beech Fern (Phegopteris hexagonoptera)

A number of ferns at the Arboretum are not commonly seen along the trails, but may occur in areas not open to the public. One of these, the Broad Beech Fern, is sometimes seen along the South Forest Loop Road and probably occurs at a variety of other sites off the trails. Some of its distinguishing characteristics are: (1) a triangular leaf shape — the leaves are typically as wide at the bases as they are long; (2) the rachis of the leaf (the central stalk) is winged; (3) the compound leaves are bipinnatified (i.e., the primary divisions of the leaf (the pinna) are themselves subdivided into secondary divisions); (4) the lowermost pinna tend to point downward; and (5) the spore-bearing structures (sori), borne on the underside of the leaf, are arranged in two rows near the center of the primary pinna and have no indusia (membranous cover). Broad Beech Fern is found throughout Tennessee, and its range extends throughout the eastern half of the US and north into most of the eastern Canadian Provinces.

Walking Fern (Asplenium rhizophyllum)

One of the most interesting ferns present at the Arboretum is the Walking Fern, typically found on moss covered, calcareous rocks in shady microhabitats. It occurs at scattered sites around the Arboretum and adjacent research areas, but is not obvious along our trails. This unique fern characteristically forms circular patches with its lance-shaped, undivided, evergreen leaves tapering to slender points arching over the mossy substrate. Where the tips touch the moist substrate, they may develop roots and new plants — thus “walking” across the substrate. The brown linear sori (spore-bearing structures) are borne on the undersurface of the leaves, more or less paralleling the network of veins. Research suggests that Walking Fern may require an exposed rock surface to become established. This member of the Spleenwort family (Asplenaceae) is found throughout eastern North America, from southern Ontario and Quebec, south to Florida, Georgia, and Mississippi, and west to Oklahoma, Kansas, Iowa, Wisconsin and southeastern Minnesota. It is known to occur throughout eastern and middle Tennessee.

Trumpet Creeper (Trumpet Vine) (Campsis radicans)

Trumpet Creeper, a native woody vine also known as Trumpet Vine or Cow-Itch Vine, blooms in mid-June in our area. It is readily identified by its yellow-orange to scarlet tubular flowers and its large, pinnately compound leaves. A member of the Bignoniaceae, Trumpet Creeper is related to Cross Vine and Catalpa. The flowers are especially attractive to hummingbirds and butterflies that feed on the abundant nectar. Ants are also common visitors to these flowers. The vine can climb to heights of 40 feet, attaching itself to supporting trees or other vertical objects by modified aerial rootlets. It may also grow horizontally along the surface of the ground, thus being referred to by some folks as the “Devil’s Shoestring.” The common name “Cow-Itch Vine” reflects the fact that its sap can be a skin irritant. Although not commonly seen at the Arboretum, it is often seen along Greenway trails in Oak Ridge and elsewhere in our region. Trumpet Creeper grows rapidly and is considered to be potentially invasive.

Ebony Spleenwort (Asplenium platyneuron)

Mid to Late June

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 (the latter described in the May Featured Plants page). 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.

Sourwood (Oxydendrum arboreum)

Mid to Late June

A small to medium-sized tree, Sourwood is found along many Arboretum trails. As a member of the Ericaceae Family, it is related to such plants as blueberries, rhododendrons, and azaleas. The white, bell-shaped flowers are borne in terminal one-sided clusters and become conspicuous in June. The fruits persist on the flower stalks often into the fall and winter. Because the flowers are often near the top of the trees, they may be difficult to see under a forest canopy. A good place to observe these trees in bloom is in a study plot of Sourwood just below the Elmore Holly Collection.

The ridged and often deeply furrowed bark of Sourwood is readily identified especially in older trees where it becomes blocky. In the fall, the leaves turn bright red. The trees 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 honey is a favorite of many.

Pipsissewa (Chimaphila maculata)

Pipsissewa, also known as Striped or Spotted Wintergreen, is a small evergreen plant with whorls of 2-3 dark green leaves having light colored mid-veins borne mainly near the base of the stem. It bears 2-5 nodding white to pink, waxy flowers in June that mature into dry brown capsules later in the year. It is in bloom along the Oak-Hickory and Lost Chestnut trails beginning in early June. The evergreen leaves can be found on the forest floor throughout the year. This species is widely distributed from the north central and eastern U.S. and adjacent Canada south to Florida and Mississippi. A closely related species, Chimaphila umbellata (also known as Pipsissewa), does not have a light colored mid-vein and has a more northern and western distribution.

The common name Pipsissewa is derived from the use of this herb by Native Americans and early settlers to treat kidney stones. It is touted by herbalists to have a variety of medicinal uses and has been used as flavoring for rootbeer and candy. Hunters have also found Pipsissewa as stomach contents in grouse during winter months, and it may be used as food by other birds and wildlife.

American Beech (Fagus grandifolia)

American Beech is a common tree found at the Arboretum. It is identified by its smooth gray bark; alternate, serrate leaves with straight, parallel veins, each ending at a tooth on the leaf margin; and elongate, pointed buds on the twigs. The yellow (turning to brown) leaves in the fall persist throughout the winter. A large beech tree is found along Marsh Road, on the left just past the Magnolia Orchard.

The tree flowers in April. Developing beechnuts can be seen now on the Marsh Road tree. When mature in the fall, the spiny fruit husk (bur) contains two (sometimes three) nuts, which are eaten by many birds and mammals. Beech wood is used for many purposes, such as flooring, furniture, plywood, railroad ties, and firewood. Beech mast is not produced every year but rather at intervals of 2 to 8 years.

Blackjack Oak (Quercus marilandica)

Blackjack Oak is one of the less common oaks along Arboretum trails. Scattered individuals can be seen along Marsh Road and elsewhere on drier sites. Its presence most likely indicates past clearing for crops and/or a history of fire. Blackjack Oak may invade disturbed sites along with Shortleaf and Virginia Pine and can remain a component of the maturing deciduous forest for many years. Its distinctive leathery leaves are broadest at the tip with 3-5 bristle-tipped, rounded lobes. The lower leaf surface is velvety and rusty brown, while the upper surface is a shiny dark green.

The bark is thick, blocky, and dark, almost black. It is found throughout the eastern US south from New York and the Midwestern states and west to Oklahoma, Texas, Kansas, and Missouri. It is a major component of the Cross Timbers bordering the plains at the western edge of its distribution, and it is also an important constituent of the Pine Barrens in New Jersey. The wood has been used to make charcoal, railroad cross-ties, and fuel.

Lizard's Tail (Saururus cernuus)

Late June to Early July

A walk in the Marsh Area reveals a large colony of Lizards-Tail (also known as Water Dragon) growing along the creek bank. This aquatic plant has an inflorescence that resembles a bottle brush made up of a dense cluster of white flowers. As the fruits mature, the brown inflorescence is said to resemble a lizards tail.

Lizard-Tail grows along ditches, streams, ponds, and in other wetland situations. It is a popular water garden plant. Over time, the plant has been used as a general medicine for a variety of illnesses. Lignan compounds and other chemicals in Lizard-Tail have been shown to provide it with chemical defense against aquatic herbivores such as crayfish. Recent biochemical studies indicate that compounds from this plant have potential for treatment of tumors.

Sassafras (Sassafras albidum)

Late June to Early July

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. This year its small greenish-yellow flowers came 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 60-70ft 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 Fil 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.

Mountain Laurel (Kalmia latifolia)

Oxeye Daisy (Leucanthemum vulgare)

Cumberland Azalea (Rhododendron cumberlandense)

Red Mulberry (Morus rubra)

Southern Magnolia (Magnolia grandiflora)

Broad Beech Fern (Phegopteris hexagonoptera)

Walking Fern (Asplenium rhizophyllum)

Trumpet Creeper (Trumpet Vine) (Campsis radicans)

Ebony Spleenwort (Asplenium platyneuron)

Sourwood (Oxydendrum arboreum)

Pipsissewa (Chimaphila maculata)

American Beech (Fagus grandifolia)

Blackjack Oak (Quercus marilandica)

Lizard's Tail (Saururus cernuus)

Sassafras (Sassafras albidum)