University of Tennessee Forest Resources Research Center

Tulip Poplar (or Yellow Poplar) is the state tree of Tennessee and is found throughout the Arboretum, where it is a prominent member of the deciduous forest replacing shortleaf and Virginia pines. Tulip Poplar is recognized by its tall straight trunks, its tulip-shaped flowers, and its distinctive leaves.

Tulip Poplar flowers appeared last week and should be noticeable this week. Because the yellow-green, tulip-shaped, upright flowers are found high in the tree canopy, they are often difficult to see. 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 - two other native members of this family are found in the Arboretum forests - Cucumber Magnolia (Magnolia acuminata) and Umbrella Magnolia (M. tripetala). Look for these native species as you walk the Arboretum trails.

Pink Lady's Slipper (Cypripedium acaule)

Last week, Pink Lady's Slippers (also known as Moccasin Flowers) began blooming at the Arboretum. These beautiful orchids, which are usually found in pine forests in our area, are gradually disapearing from the Arboretum as deciduous forests replace the pines.

The common names "Slipper" and "Moccasin" refer to the conspicuous pink pouch of the flower (the labellum). The flower attracts bees, which enter a slit down the front of the pouch; once inside, a bee must exit through the rear of the flower, thus ensuring pollination.

Over the years, Lady's Slipper populations on the White Pine Trail have been removed by vandals and have not become reestablished. Look for Lady's Slippers on the upper forested slope as you walk along the Marsh Road. If you are fortunate enough to see one of these plants, please stay on the road to avoid disturbing the plant or its habitat.

Yellow Buckeye (Aesculus octandra)

Yellow Buckeye was in full bloom this past week—several large trees can be seen near the Marsh Area of the Arboretum. You will also see many young buckeyes with palmate compound leaves of 5 leaflets along the Tulip Poplar Trail, the Old Kerr Hollow Road, and the Cemetery Ridge Trail.

The common name “Buckeye” is based on the large brown seed with a large pale scar that looks like the eye of a deer. The Buckeye seeds are poisonous. Other species of the genus Aesculus you may see in the area include Horse Chestnut—frequently planted in urban areas, Red Buckeye—a small tree or shrub with red flowers, and Ohio Buckeye—distinguished by the rank odor of crushed leaves or stems.

Kousa Dogwood (Cornus kousa)

Kousa Dogwood - varieties known as Chinese Dogwood and Japanese Dogwood - is a small, showy ornamental tree in full bloom at the northeast edge of the Visitors' Center parking lot on your left as you walk up Valley Road into the Arboretum. Because of its disease resistance to dogwood anthracnose, it is frequently planted as an alternative to the native flowering dogwood.

Kousa dogwood flowers about a month later than the flowering dogwood. Its crown is wider than tall and is relatively small in stature - 20-30 ft tall. As with flowering dogwood, the small inconspicuous green flowers are surrounded by large white, showy bracts. Its red fruits are said to look like big round raspberries. Fall colors range from dull red to maroon. The attractive bark is exfoliating (comes off in flakes.)

Jack-in-the-Pulpit (Arisaema triphyllum)

Jack-in-the-Pulpit, a late spring wildflower, is found throughout the Eastern U.S. Numerous examples are present in the Arboretum’s wildflower garden next to the Visitors Center. Its unusual inflorescence is enclosed by a purple- to green-striped sheathing bract (the pulpit) called a spath. The inflorescence (the Jack) is called a spadix and consists of a fleshy axis covered with tiny flowers.

Jack-in-the-Pulpit has been used for medicinal purposes. Although parts of the plant are considered edible, they contain calcium oxylate crystals which when eaten raw can cause irritation or serious breathing problems.

The compound basal leaves have 3 leaflets that superficially resemble poison ivy.

Another member of the genus Arisaema that can be seen in our wildflower garden is the Green Dragon (A. dracontium) which has a narrow greenish-yellow spath.

Christmas Fern (Polystichum acrostichoides)

Christmas fern is found in many places along the Arboretum trails. It grows in distinctive clumps with its relatively large evergreen fronds (leaves) growing up to 2.5 feet in length. At this time of year, the fertile fronds bear brown sori (spore-bearing structures) on the undersides of the upper third of the fertile fronds.

The name Christmas fern is based on the practice in the past of collecting its evergreen leaves for Christmas decorations; also the shape of the pinnae (leaflets) resembles that of a Christmas stocking. Christmas fern is frequently planted for groundcover, especially in shady areas and on slopes. Because it is evergreen and has a well-developed underground rhizome system, it is used in landscaping to help control soil erosion.

Japanese Honeysuckle (Lonicera japonica)

Japanese Honeysuckle is an exotic, invasive vine that is conspicuous at this time of year along forest edges, fence rows, and in forest canopies. Its very fragrant, white tubular flowers, which turn yellow with age, are borne in pairs at the leaf nodes. A long tube inside the corolla is filled with a honey-like nectar. Children enjoy removing the white blossom and sucking out the few drops of sweetness from the long inner tube — thus the common name “Honeysuckle.”

A native of Japan and China, this vine can climb more than 30 ft and spread over a tree’s canopy to the point of shading it out and killing the tree. Its runners can also twist tightly around the stems of smaller plants and essentially strangle them by cutting off their supply of water through the xylem cells. Japanese Honeysuckle was introduced to the U.S. in the 1860s and has spread throughout much of the country.

Indian Pink (Spigelia marilandica)

Over Memorial Day weekend, Indian Pink (also known as Pinkroot or Wormgrass) was in bloom along the Heath Cove Trail. The scarlet corolla tube, which is yellow-green on the inside, flares to five yellow to white reflexed points. These flowers are very attractive to hummingbirds, and the plant is rated as one of the top hummingbird plants for gardens.

In the past, the roots of Indian Pink have been used for medicinal purposes — for expunging intestinal worms, for endocardial problems, and as a cough medicine. However, its active ingredient is the alkaloid spigeline, which can be toxic at high doses. Spigelia ranges throughout the southeast, west to Texas and north to Indiana.

Fly Poison (Amianthium muscitoxicum)

Late May - Early June

Fly Poison or Stagger Grass is a member of the Lily Family and is conspicuous along the Oak-Hickory Trail 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.

All parts of the plant are toxic, especially the bulb. In the past, sugar or honey mixed with crushed portions of the bulb was used to kill flies. Cattle and sheep may eat the plant when other forage plants are limited. 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."

Mountain Laurel (Kalmia latifolia)

Late May thru Early June

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.

Tulip Poplar (Liriodendron tulipifera)

Pink Lady's Slipper (Cypripedium acaule)

Yellow Buckeye (Aesculus octandra)

Kousa Dogwood (Cornus kousa)

Jack-in-the-Pulpit (Arisaema triphyllum)

Christmas Fern (Polystichum acrostichoides)

Japanese Honeysuckle (Lonicera japonica)

Indian Pink (Spigelia marilandica)

Fly Poison (Amianthium muscitoxicum)

Mountain Laurel (Kalmia latifolia)