University of Tennessee
Forest Resources AgResearch and Education Center
Oak Ridge Forest Cumberland Forest Highland Rim Forest Arboretum

July

There is always something in bloom at the Arboretum! Use our Plants Library to plan a photo shoot or to choose one of the trails to walk. Learn more about the plants at the Arboretum by visiting our Previously Featured Plants list and our Special Seasonal Featured Plants page.


Sourwood (Oxydendrum arboreum)

Sourwood in Flower Sourwood Flowers 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.

Sourwood Fall Leaves Sourwood Bark 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.

Daylilies (Heremocallis species)

Daylily 1 Daylily 2 Daylily 3
UT Arboretum Society volunteers planted approximately 50 Daylily cultivars adjacent to the Arboretum parking lot in the spring of 2013. These plants, which begin blooming in early June, were donated by Peter Shea from his extensive garden.

Daylily 4 Daylily 5 Daylilies, native to China, Korea, and Japan, were imported to Europe as early as the 16th Century. Thousands of named cultivars have been developed that differ in such features as flower color and shape, or time and season of blooming. Clumps of linear, grass-like leaves give rise to individual, leafless stalks usually bearing several flower buds. Each flower has three petals and three sepals which resemble each other (collectively called tepals). For most cultivars, the flowers open one at a time and last a single day — this trait is reflected in the common name Daylily and the scientific name Heremocallis (from the Greek meaning “beauty for a day”). Daylilies thrive in many different climatic zones and habitats. Although the flowers are similar to those of true Lilies, Daylilies belong to a separate plant family, the Xanthorrhoeaceae.

Red Mulberry (Morus rubra)

Red Mulberry Red Mulberry is a relatively small tree (30-80 ft tall) 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 Superintendent’s House along the Valley Road. Red Mulberry is found throughout the Eastern U.S., but it is disappearing in parts of New England and Michigan, possibly due to bacterial disease. It typically occurs as scattered individuals in a variety of moist forest habitats and along fence rows and roads.

The alternate, serrate leaves are ovate to orbicular in shape and vary from being highly dissected and lobed to non-lobed — our trees tend to have few if any lobes. Red Mulberry is commonly dioecious (i.e., with separate male and female trees), but can be monecious with both male and female flowers on the same tree (see photo below).

Red Mulberry Flowers Red Mulberry Fruit In late May and June you can find Red Mulberry fruits ripening. When mature, the black fruits, resembling elongated blackberries, are favorite foods for many birds and small mammals such as squirrels, opossums, and raccoons. The juicy aggregate fruits have been used for jams, pies, and wines. The decay-resistant wood is used for fence posts, furniture, caskets, 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. Unripe fruits and the milky sap are poisonous. Pollen from Red Mulberry is a severe allergen.

Dawn Redwood (Metasequoia glyptostroboides)

Dawn Redwood - Summer Dawn Redwood - Fall Dawn Redwood is a deciduous conifer with flat, needle-like leaves that turn a copper-colored brown in November. A specimen of this tree, planted in 1965, can be seen in the Arboretum’s Central China Collection near the end of Marsh Road. Dawn Redwood is related to Bald Cypress (Taxodium distichum) of the southeastern U.S. and to California’s Redwood (Sequoia sempervirens) and Giant Sequoia (Sequoiadendron giganteum).

Dawn Redwood Leaves In the early 1940s, a Chinese paleobotantist recognized that fossils initially thought to belong to the genus Sequoia, should be reassigned to a new genus, Metasequoia. In 1945, living individuals of Metasequoia glyptostroboides were found in the Sichuan Province of China. Extensive field surveys in the late 1940s found this “living fossil” present in limited populations in both Sichuan Province and neighboring Hubei Province. Propagation of seeds and cuttings at arboreta in the U.S. and elsewhere resulted in Dawn Redwood becoming available for planting. Although Dawn Redwood does not have wide-spread commercial value, its lumber is similar to that of Coastal Redwood and has been used to make furniture as well as pulp for making plyboard and composite materials.

Dawn Redwood Pollen Cones Dawn Redwood Trunk Metasequoia is a fast growing tree — some of the oldest U.S. trees (planted in 1948) have attained diameters of over 1 meter. Dawn Redwood can be distinguished from Bald Cypress by several characteristics — the buds develop on the underside of the branches not along the tops; the leaves are opposite, not alternate; the base of the trunk is fluted and buttressed; and the branches have rounded depressions below their junction with the trunk. The light brown pollen cones are borne on long stalks appearing in early spring; the inconspicuous female cones are borne singly.

Tulip Poplar(Liriodendron tulipifera)

Tulip Poplar Leaves Tulip Poplar Bark Tulip Poplar (also called Yellow Poplar) is the state tree of Tennessee and a prominent member of the Arboretum’s deciduous forest. It is found throughout Eastern North America, from southwestern Ontario and Michigan, south to Louisiana and Florida. It is one of the largest native trees in U.S. eastern forests, growing to heights of 80 to 150 ft. Tulip Poplar is recognized by its tall straight trunks, its tulip-shaped flowers, and its distinctive 4-lobed, shiny green leaves that are pale underneath. The thick bark of mature trees is deeply furrowed with narrow, rounded ridges.

Tulip Poplar Flowers The upright yellow-green, tulip-shaped flowers with a deep orange band near the base are found high in the tree canopy and are often difficult to see. In May, look for yellow to cream flower parts on the ground beneath the trees; then look up to see the flowers. Tulip Poplar belongs to the Magnolia Family; three other native members of this family are found in the Arboretum forests — Cucumber Magnolia (Magnolia acuminata), Umbrella Magnolia (M. tripetala), and Bigleaf Magnolia (M. macrophylla).

The light, brittle wood of Tulip Polar is used for furniture, plywood, oriented strand board (OSB), and pulpwood. It was used by Native Americans to make dugout canoes. Tulip Poplar’s rapid growth and high commercial value for lumber makes it suitable for reforestation.

Invasive Shrubs, Vines, and Trees

Invasive plants are non-native species that aggressively invade areas and displace native species. These plants may have been introduced by gardeners or transported from other countries by accident. Examples of invasive shrubs, vines, and trees commonly encountered at the Arboretum are shown below. These species are listed in the “Severe Threat” category by the Tennessee Exotic Pest Plant Council (tneppc.org/invasive_plants) and present management challenges as well as research opportunities. More detailed descriptions of these can be found by clicking on the individual links below.

Autumn Olive

Chinese Privet

Autumn Olive
(Eleagnus umbellata)

Chinese Privet
(Ligustrum sinense)

Multiflora Rose

Mimosa

Multiflora Rose
(Rosa multiflora)

Mimosa
(Albizia julibissin)

Japanese Honeysuckle

Oriental Bittersweet

Japanese Honeysuckle
(Lonicera japonica)

Oriental Bittersweet
(Celastrus orbiculatus)

Tree-of-Heaven

Princess Tree

Tree-of-Heaven
(Ailanthus altissima)

Princess Tree
(Paulownia tomentosa)


View a list of Previously Featured Plants

Please help us preserve our natural heritage!
No collecting of plant materials is permitted at the UT Arboretum.

University of Tennessee - Forest Resources AgResearch and Education Center
901 South Illinois Avenue, Oak Ridge, Tennessee 37830 · Telephone: 865-483-3571 · Email: UTforest@utk.edu