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

May

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.


Fly Poison (Amianthium muscitoxicum)

fly Poison Fly Poison (also known as Stagger Grass) is a member of the Lily Family and is conspicuous from April through June. It has grass-like basal leaves and at full bloom a spectacular cylindrical, white inflorescence. Although the distribution of Fly Poison is reported to be throughout the Southeast, extending as far west as Oklahoma and as far north as New York, it is found infrequently in a range of habitats from wetlands to pine-oak forests. At the Arboretum, it can be seen along the Oak-Hickory and Backwoods trails.

Fly Poison Flower Fly Poison Plant All parts of the plant are toxic, especially the bulb. In the past, a mixture of sugar or honey and crushed portions of the bulb was used to kill flies. Cattle and sheep may eat the plant when other forage plants are not available. The toxic alkaloid contained in the plants can cause the animals to stagger around before dying - thus the origin of the common name "stagger grass."

Red Buckeye (Aesculus pavia)

Red Buckeye In mid-April, a Red Buckeye is in full bloom next to the Arboretum Visitors Center. This tree belongs to the Soapberry Family (Sapindaceae). It is one of four Buckeye species in East Tennessee— other buckeyes found in our area include Yellow Buckeye (A. flava), Ohio Buckeye (A. glabra), and Painted Buckeye (A. sylvatica). Horse Chestnut (A. hippocastanum), which is frequently planted in urban areas, is also a member of this genus.

Red Buckeye Branch Red Buckeye Flower Red Buckeye is found throughout the Southeastern U.S. in mesic deciduous woods, low woodlands, swamp margins, and along river edges. This small tree typically grows to heights of 15-20 ft, but occasionally it can attain heights up to 35 ft or more. As with other buckeyes, it had opposite, palmate leaves with 5 shiny green leaflets. The bright red tubular flowers, borne in erect panicles, have 4 petals. These flowers provide an early food source for migrating hummingbirds and butterflies. In the autumn Red Buckeye produces pear-shaped brown fruits with 1-2 glossy brown seeds, which contain saponins, a substance toxic to humans. Red Buckeye is often used for landscape plantings. The roots have been used to make soap, and the wood to make a black dye. Native Americans placed crushed seeds and other parts of the plant in water to “drug” fish—causing them to float to the surface for easier catching.

Trillium (Trillium species)

Trillium grandiflorum Trillium cuneatum Trillium luteum
April brings with it a beautiful display of Trilliums along many of the Arboretum’s trails. There are at least three species of Trillium present: Large-Flowered Trillium (Trillium grandiflorum) has a stalked large white flower and large dark green leaves. Sweet Betsy (T. cuneatum) and Yellow Trillium (T. luteum) have upright sessile flowers (no stalk) and mottled leaves—they differ in flower color, with the former being maroon to bronze and the latter yellow. These plants are especially conspicuous along the Heath Cove and Oak-Hickory trails.

The name Trillium comes from a Greek word “tris” meaning three. The leaves and flower parts of Trillium all occur in “3s.” Species with sessile flowers (no flower stalks) are commonly known as “Toadshades,” while those with stalked flowers are known as “Wakerobins.” Trillium leaves are said to be edible, and the leaves and roots have been used for medicinal purposes.

Trillium grandiflorumAn interesting group of Trillium cuneatum and T. luteum is present along Old Kerr Hollow Road. This population has both yellow and maroon flowers, with others having intermediate colors between the two. Such populations may represent a hybrid swarm - i.e., a population of interbreeding hybrids.

Redbud (Cercis canadensis)

Redbud Blossoms One of the most beautiful and conspicuous trees at the Arboretum in April is the Redbud. This tree is most commonly seen at forest edges, in disturbed areas, or in managed landscapes. Redbud is a member of the bean family (Fabaceae), and in a natural setting is an early invader of disturbed areas where it grows quickly but is generally short lived (20-25 years). Distinguishing characteristics of Redbud include its rose-pink, pea-like flowers, its heart-shaped leaves, and its flat, brown, bean-like pods.

Redbud At the Arboretum you will see Redbud along several trails and bordering some open areas. A research planting near the Program Shelter is in full bloom. The larger trees in this area are survivors of a failed research study originally planted in 1995. A new planting of redbuds was made in 2007 next to these older trees; the young trees are just becoming established. The objective of the current study is to evaluate Chinese Redbuds and ones from a northern location in the United States for potential introduction in Eastern Tennessee.

March Wildflowers

Once winter recedes in early March, one anticipates seeing a variety of early spring wildflowers along Arboretum trails. Here are several of the more common ones you may encounter.

Bloodroot

Yellow Trillium

Bloodroot
(Sanguinaria canadensis)

Yellow Trillium
(Trillium luteum)

Slender Toothwort

Roundlobe Hepatica

Slender Toothwort
(Dentaria heterophylla))

Roundlobe Hepatica
(Hepatica americana)

Spice Bush

Azure Bluet

Spicebush
(Lindera benzoin)

Azure Bluet
(Houstonea caerulea)


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