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Special Seasonal Featured Plants

The Arboretum is a place for all seasons! Use these special seasonal features to plan a photo shoot or to choose one of the trails to walk. To learn more about the plants at the Arboretum visit our Plants Library or our Previously Featured Plants pages.


An April Walk At The Arboretum

An April Walk At The Arboretum



Magnolia Orchard

A major Arboretum attraction in March and April is the Magnolia Orchard near the Visitors Center, which presents both a colorful landscape and a delightful bouquet. This research orchard of hybrid magnolias was established in 1966 to evaluate their susceptibility to late spring frosts. A variety of the blooming hybrids is shown below.


Magnolia Orchard Lower Planting Magnolia Orchard Upper Planting

Left: Lower Planting, Right: Upper Planting


Magnolia Orchard


Winter-Green Trees

The Arboretum supports a variety of native and exotic evergreen trees that are particularly apparent during winter months when deciduous trees have lost their leaves. Not all these trees are conifers; for example the Southern Magnolia keeps its leaves during the winter months, but then sheds them over the spring. Some of our more common winter-green trees include the following:


Winter-Green Trees


Hollies (Ilex species)

Hollies Hollies have been associated with the winter solstice since ancient times. They are found throughout the world occupying a wide range of habitats. More than 780 evergreen hollies and 30 deciduous hollies have been recognized. Although North America is not considered a major center of holly diversity, it does have 23 native hollies, with 7 occurring in Tennessee. Many holly cultivars have been developed and are used extensively in landscaping. Hollies have a rich history of medicinal uses and have been regarded as religious symbols. They are also used widely for wreaths and other holiday decorations.

American Holly (Ilex opaca) is found as an understory tree in a variety of habitats throughout the Arboretum. Although it can grow to heights of 50 to 60 feet, most of the trees along the trails are much smaller, reflecting their slow growth rate and the relatively recent disturbance history of our forests. After leaf fall in the autumn, American Hollies with their spiny, evergreen leaves become more readily visible. The fruits (4-seeded drupes) are collected along with the leaves for Christmas wreaths and other holiday decorations. The fruits are eaten by birds and small mammals, but can be toxic to humans and pets. The wood is suitable for inlays in cabinet work, handles, carvings, rulers, and scientific instruments. When dyed black to resemble ebony, the wood is used for violin pegs, piano keys, and fingerboards.

The Harold L. Elmore Holly Collection at the UT Arboretum is a research and display garden containing over 200 evergreen and deciduous Holly cultivars. The collection is named in honor of the late Harold Elmore, a past president of the University of Tennessee Arboretum Society and the Holly Society of America. It is recognized by the Holly Society of America as an official collection of Hollies, and was written up in the Tennessee Farm Bureau’s Home and Garden Magazine (Fall 2014). Other Holly plantings are found in the Marsh Area and along Valley Drive and Shade Tree Lane.

Fall Foliage


Scarlet Oak

Red Maple

Mockernut Hickory

Muscadine Grape

Ginkgo

Sassafras

Bald Cypress

Black Oak
1 2 3 4 5 6 7 8

Fall leaf colors at the Arboretum peak during October. A hike along any one of our numerous trails will provide an opportunity to see a variety of trees, shrubs, and vines displaying leaf colors ranging from bright red to yellow to orange. Some of the more impressive species are shown here.


Fall Wildflowers 2014

Fall Wildflowers 2014

Early Spring Wildflowers

Many spring wildflowers can be seen along Arboretum trails in March and April. Six of the more common early bloomers are shown here:

Roundlobed Hepatica Bloodroot Bluets

Holly Mayapple Sweet Betsy


Spring Blooms

Many trees and shrubs at the Arboretum burst into bloom during the month of April. A research collection of Redbuds is found along Arboretum Drive near the Program Shelter; plantings of Azaleas can be seen near the Visitors Center and the Heath Cove Trail; the Magnolia Garden near the Visitors Center contains many different Magnolia hybrids; a Flowering Dogwood research collection is present between the Tulip Poplar Spur trailhead and the Program Shelter; and Tulip Poplar, a common tree of our deciduous forests, can be seen along many of the Arboretum trails.


Redbud
Redbud

Coral Bell Azalea
Coral Bell Azalea

Saucer Magnolia Hybrid
Saucer Magnolia

Star Magnolia
Star Magnolia

Tulippoplar
Tulip Poplar

Flowering Dogwood
Flowering Dogwood

Mast

White Oak Acorns Chinese Chestnut Bur Beechnut Fruit Hickory Nuts


As late summer transitions into fall, hikers along the Arboretum's trails are likely to encounter numerous acorns, hickory nuts and other fall fruits. The quantity of these fruits, collectively referred to as mast, can vary strikingly from year to year. The term 'mast' comes from an ancient Anglo-Saxon word referring to nuts and fruits on the forest floor that provided food for hogs and other domesticated animals. Today the term is used more generally to refer to fruits produced by woody plants that provide food for wildlife.

A distinction is made between hard and soft mast. Hard mast consists of hard shelled fruits and seeds (e.g., acorns, hickory nuts, beechnuts, black walnuts, pine seeds) which are high in carbohydrates, fats, and proteins. Hard mast generally matures in the late summer and fall and may persist into winter months. It can provide an important source of food for wildlife when other food is scarce. Soft mast, on the other hand, refers to fleshy fruits (e.g., black cherries, blackberries, raspberries, muscadines, persimmons, serviceberries) having a high content of sugars, vitamins, and carbohydrates. Soft mass is usually unavailable during winter months, but it can play a role as a source of moisture for wildlife during dry periods and as a food source for migratory birds.


Paw Paw Fruit Muscadine Grapes Raspberries Mulberry Fruit


An intriguing aspect of hard mast, in particular, is the variability in the amount produced in any given year. While a number of theories have been advanced to explain this variability, none of the reasons for yearly fluctuations in mast production appear to be conclusive. Weather and local climate fluctuations, however, clearly play an important role. In high mast years, the abundant supply of available food in the fall and winter can contribute to wildlife survival and reproduction, while in lean years, wildlife may be forced to forage widely for food, and populations may decline.


Acorns
(Quercus species)

White Oak Acorns Chestnut Oak Blackjack Oak Post Oak Bur Oak

(From left: White Oak, Chestnut Oak, Blackjack Oak, Post Oak, Bur Oak)


An acorn is the fruit of an Oak tree — a single-seeded nut covered by a woody cap (cupule). These fruits contain tannins that are toxic in large amounts to most domestic animals, with the notable exception of pigs. Acorns, however, are an important food for deer, bear, squirrels, turkeys, and other wildlife. In years when acorn production is low, wildlife populations may decline and foraging wildlife may create problems. When soaked to remove the tannins, acorns provided a food staple for Native Americans. They have also been used as a coffee substitute, when coffee was unavailable.

A diversity of oaks can be found along our Arboretum trails and in the Oak Collection near the Program Shelter. Some of the more common acorns you might find at the Arboretum in the fall, illustrated below, have distinct characteristics that aid in identifying the species.


Black Oak Acorns Southern Red Oak Scarlet Oak Sawtooth Oak Shingle Oak

(From left: Black Oak, Southern Red Oak, Scarlet Oak, Sawtooth Oak, Shingle Oak)


Deciduous Hollies

'Winterberry' Holly'Winterberry' (Ilex verticillata) is one of several deciduous hollies present in the Arboretum’s Marsh Area. These are part of the Elmore Holly Collection which is described in detail - including a full list of the collection and a site map.

Although one usually thinks of hollies as being evergreen, a variety of hollies lose their leaves each fall and provide a display of bright colored fruits at this time of year. 'Winterberry' is one of three native deciduous hollies found in East Tennessee - the others being Carolina Holly (Ilex ambigua v. amigua) and Mountain Holly (Ilex ambigua v. montana). Many culivars and hybrids using Winterberry have been developed including the four examples shown below that can be seen in the Marsh Area this winter.

'Winter Gold' Holly 'Bonfire' Holly

Left: 'Winter Gold' (Ilex verticillata)
Right: 'Bonfire' (Ilex serrata x verticillata)
'Stop Light' Holly 'Earlibright' Holly

Left: 'Stop Light' (Ilex verticillata)
Right: 'Earlibright' (Ilex verticillata)

Winter Fruits

As one walks the Arboretum trails at this time of year, the fruits of a variety of woody plants and vines can be seen. Our native Dogwood, American Holly and Greenbriar are found along with several non-native, invasive plants, such as Oriental Bittersweet, Chinese privet, and Amur Honeysuckle. Some of these fruits, such as those of the Dogwood provide food for a variety of birds (e.g., robins, cedar waxwings) and small mammals. Six of the more common winter fruits found at the Arboretum are described below.

Flowering Dogwood Fruit Oriental Bittersweet Fruit

Left: Flowering Dogwood (Cornus florida)
Right: Oriental Bittersweet (Celastrus orbiculatus)
American Holly Fruit Chinese Privet Fruit

Left: American Holly (Ilex opaca)
Right: Chinese Privet (Ligustrum sinense)
Amur Honeysuckle Fruit Greenbriar species Fruit

Left: Amur Honeysuckle (Lonicera maackii)
Right: Greenbriar species (Smilax sp.)

Three Common Native Pines (Virginia Pine, Shortleaf Pine, White Pine)

Virginia Pines Virginia Pine (Pinus virginiana) has scaly bark, twisted needles in bundles of 2, and small, reddish brown cones. The trunks usually have numerous dead branch stubs along their axes. The dull green to yellowish spreading needles are 1.5 to 3 in. long. The cones are 1.5 to 2.5 in. long with a sharp spike or prickle at the end of the seed scale. This fast growing tree can grow on poor sites and is often used in reclamation, for pulpwood, and as Christmas trees.

Shortleaf Pines Shortleaf Pine (Pinus echinata) is an important commercial tree species of the Southeastern US. It has straight, flexible needles, 3 to 5 inches long in bundles of 2 or 3, that are dark yellow-green in color. The reddish brown cones are egg-shaped, 2 inches long, with a small prickle on the end of the seed cone scales. Older tree bark develops flat scaly plates that have very small resin pockets. The wood is used for a variety of purposes, including lumber, plywood, and pulpwood.

White Pines White Pine (Pinus strobus) is found throughout northeastern Canada and the US, extending down the Appalachians. Its blue-green, flexible needles, 3-5 inches long are borne in bundles of 5. The stalked cylindrical cones are 4 to 8 in. long and are very resinous. The bark of young trees is smooth and gray-green, but as the trees mature, it becomes thicker and darker with scaly furrows. Historically, White Pine was used for masts for sailing ships. It is an important lumber tree and is planted for ornamental purposes in landscaping and for Christmas trees.

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
Autumn Olive
(Eleagnus umbellata)

Chinese Privet
Chinese Privet
(Ligustrum sinense)

Multiflora Rose
Multiflora Rose
(Rosa multiflora)

Mimosa
Mimosa
(Albizia julibissin)

Japanese Honeysuckle
Japanese Honeysuckle
(Lonicera japonica)

Oriental Bittersweet
Oriental Bittersweet
(Celastrus orbiculatus)

Tree-of-Heaven
Tree-of-Heaven
(Ailanthus altissima)

Princess Tree
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