Hackberry (Celtis occidentalis)

Hackberry, a member of the Elm family (Ulmaceae), is a tree found throughout much of the Eastern U.S. and adjacent Canada, south to Florida, and west through the Great Plains. It occurs on moist bottomland soils and somewhat drier sites with limestone derived soils. Several good examples of Hackberry can be seen along Arboretum trails. One is located near the start of the South Forest Loop Road just downhill from the entrance to the Cemetery Ridge Trail. There are also several Hackberries along the Heath Cove Trail, three at its entrance on the Valley Road, and another at the top of the loop before proceeding uphill to the Program Shelter.

Hackberry leaves are ovate in shape, being wide at the base and tapering to the tip. The leaf tip margins are toothed (serrate), and the leaf base tends to be asymmetrical. The light brown to gray bark of older trees is typically warty.

The dark orange to purple fruits ripen in September. These fruits are eaten and widely dispersed by birds (e.g., wild turkeys, grouse, and quail) and other wildlife. Sugarberry (Celtis laevigata), a closely related species, is hard to distinguish from Hackberry - one feature is that Sugarberry's long leaves differ from those of Hackberry in having mostly smooth edges with few teeth.

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Hardy Orange (Poncirus trifoliata)

An unusual and interesting shrub is located at the edge of the Shade Tree Collection near the top of the Tulip Poplar Trail Spur. Hardy Orange (or Trifoliate Orange) is a member of the Rutaceae plant family and closely related to the Citrus genus. It is a native of China and Korea that has been introduced into the US. In parts of the Southeast, it has escaped cultivation and can be an invasive species in fencerows, roadsides, and forest edges. The compound leaves have three leaflets, and the branches terminate in conspicuous thorns.

Although the green fruit, which turns dull yellow in the fall, has been used for making marmalade, it may cause severe stomach pain, nausea, and skin irritation. Hardy Orange is a cold hardy, disease resistant plant that is used as a root stock for commercial citrus. Historically, it was planted for hedgerows because its vicious thorns make it virtually impenetrable. Thus its presence can indicate abandoned home sites.

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Harry Lauder's Walking Stick
(Corylus avenella) 'Contorta'

A recent addition to the Arboretum's plant collections near Scarborough Creek below the Visitors Center is a shrub with highly contorted branches. Harry Lauder's Walking Stick (also known as Contorted Filbert or Corkscrew Hazel) is a cultivar of European Hazel and belongs to the same genus as American Hazelnut and Beaked Hazel, both of which can be found in Tennessee. A larger specimen of Harry Lauder's Walking Stick has been growing for many years with the Arboretum's Dwarf and Unusual Conifer Collection.

This cultivar is named after a famous Scottish comedian and singer who used a crooked cane as a prop during his performances in the late 1800's and early 1900's. He traveled widely and was knighted in 1919 by King George V for his many contributions to the war effort during World War I. He continued supporting the troops during World War II. The curling, twisted branches are most conspicuous during the winter after leaf fall.

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American Hornbeam (Carpinus caroliniana)

American hornbeam (also known as ironwood, muscle-wood, blue beech) grows abundantly along Old Kerr Hollow Road. The maturing fruit clusters are apparent in mid-July, hanging down from the canopy. These consist of a 4-6 inch stalk with a series of 3-lobed, leaf-like bracts - the small nutlets are found at the base of these bracts. A related tree, European Hornbeam, is found along the Heath Cove Trail.

Common names of this tree are related to its bark and wood. The dense wood dulls woodworking tools (ironwood) and takes a horn-like polish (hornbeam). The muscle-like bark has sinewy, muscle-like ripples, (muscle-wood) and its otherwise smooth, blue-gray appearance resembles beech bark (blue-beech). The wood has been used for tool handles, bowls, and ox yokes. The fruits and buds are eaten by birds, squirrels, and deer. This understory tree occurs along streams and other low areas throughout the eastern U.S.

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Hemlock (Tsuga canadensis and T. caroliniana)

Two native species of Hemlock occur in East Tennessee. Eastern Hemlock is a wide ranging species in the Eastern U.S., and Carolina Hemlock is found only in the Southeast. Eastern Hemlock ranges from southern Canada south through the Mid-Atlantic states and the Appalachians to Alabama and Georgia and west to the Upper Midwest. In our region, Eastern Hemlock is typically found on northern or eastern exposures where the microclimate is cooler and moister than on surrounding topography or in the mountains above 2000 ft. Carolina Hemlock is often found on somewhat drier sites, although the two species may be found together in the same stand. Eastern Hemlock has shorter needles than Carolina Hemlock, and the needles tend to be in two ranks rather than spreading in all directions from the twigs.

The Hemlock Wooly Adelgid (Adelges tsugae), an invasive insect that is devastating hemlock forests throughout much of the Southeastern U.S., has been found on the Arboretum's trees this spring. Although the insect is not evident in our trees at this time of year, it is likely to become manifest in coming years and will require treatment if the trees are to be preserved.

A unique plant at the Arboretum, Valentine's Weeping Hemlock, is found near the Dwarf and Unusual Conifer Collection on the Main Drive. This plant was collected near Cosby, Tennessee, in 1940 by William L. Valentine and planted in his nursery. It was moved to the UT Arboretum in 1966. Children visiting the Arboretum love to climb under and around this unusual plant.

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Hickories (Carya spp.)

A variety of hickories occur in the Arboretum forests. Identifying a tree as a hickory is relatively easy - it has alternate, compound leaves (several leaf blades associated with each axillary bud) with 5 to 9 leaflets. Identifying the species of hickory, however, is more challenging and often requires determining characteristics of the leaves, hickory fruits (outer husks and nuts), the terminal buds, and the bark. Furthermore, there is considerable variation of these characteristics within a species and hybridization of species produces individuals with intermediate or mixed characteristics. Three of the more common hickories found at the Arboretum are described below.

Pignut Hickory (C. glabra) leaves typically have 5 to 7 glabrous leaflets (i.e. without hairs). The pear-shaped to ovoid fruits are about 1 inch in diameter, with thin husks and nuts that are not ribbed. The bark is relatively tight, has vertically oriented ridges that are rounded, and may be flaky.

Mockernut Hickory (C. tomentosa) has leaves with 7 to 9 leaflets that are pubescent on the undersides. The globular to oval fruits are about 1 1/4 inches in diameter, with thick husks and a 4-ribbed nut. The tight bark has flat to rounded, interlaced ridges.

A few Shagbark Hickories (C. ovata) are found along our trails. Their leaves usually have 5 essentially glabrous leaflets. The 1 1/2 inch diameter fruit has a thick, rounded husk that splits all the way to the base, and a nut ridged on 4 sides. The distinctive bark is broken into long, shaggy plates.

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Hollow Joe Pye Weed (Eupatorium fistulosum)

Hollow Joe Pye Weed, a member of the Aster Family with a head of pink disk flowers (no ray flowers), can be seen along Scarboro Creek near the Arboretum entrance. This type of Joe Pye Weed (also called Trumpet Weed) grows up to 10 ft in height and can be distinguished from similar Eupatorium species by its purplish colored, hollow stems, and whorls of 4-7 simple leaves at each node of the stem. This plant is attractive to many insect pollinators such as butterflies, bees, and wasps.

Other types of Joe Pye Weed include Sweet-scented Joe Pye Weed (E. purpureum), a more northern species with solid green stems and 3-4 leaves at each node, and the smaller Spotted Joe Pye Weed (E. maculatum), with spotted purple, solid stems and flat-topped flower heads.

Various accounts have identified Joe Pye as an Algonquin Indian or a white man who used the plant for treating typhus. The hollow stems were used as straws and blow guns. The plant was also used for a variety of internal and external medicinal uses. Apparently there is little, if any, scientific support for its medicinal values. Hollow Joe Pye Weed is found in moist areas along streams, ditches, and roadsides, and in upland fields and meadows.

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Honey Locust (Gleditsia triacanthos)

As you walk along Marsh Road, you will find two large trees with large thorns on their trunks. These Honey Locusts (or Sweet Locusts) have abundant yellowish, bean-like pods hanging down from the branches. The compound leaves are bi- or tri-pinnate (leaves divided two or three times). The native range of Honey Locust extends from central Pennsylvania south along the Appalachians to Alabama and west to Texas and the Central U.S.

Honey Locust belongs to the plant family Fabaceae (the bean or pea family). The large pods, which are yellowish now, turn brown as fall progresses and may persist into winter. The pods are sweet and eaten by cattle, hogs, and wildlife (thus the name "honey" or "sweet"), and the rattling of the seeds in the pods is said to resemble the singing of locusts (thus the second part of the common name).

The conspicuous thorns on the trunk and limbs are modified branches-they occasionally bear leaves. These have likely evolved over geologic time as protection against large herbivores. In the past, the very hard thorns have been used as nails, for carding wool, and as pins for closing sacks. The durable wood has been used for railroad ties, fence posts, and pallets. A number of thornless varieties have been developed for shade and ornamental use.

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Indian Pink (Spigelia marilandica)

Over Memorial Day weekend, Indian Pink (also known as Pinkroot or Wormgrass) blooms in late May 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.

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