University of Tennessee Forest Resources Research Center

A major research collection of Cornelian Cherry Dogwood cultivars is present along Arboretum Drive and behind the Juniper Garden and Conifer Collection. Cornelian Cherry Dogwood is a multi-stemmed, small tree or shrub native to Central and Southern Europe and Western Asia. The fruit, which matures in summer, is bright red and olive-shaped. In its native habitat the fruit is used for syrup and jams. This Dogwood is one of the earliest flowering trees at the Arboretum - the first blooms were evident in the collection this past week (February 17). The numerous, small yellow clusters of flowers appear before the leaves. The objective of the ongoing research study is to identify plants with exceptional ornamental value (flowering, fruiting, and form) that are hearty in this climate. The seeds for the collection were obtained from native trees in Rumania and Croatia.

Winter Jasmine (Jasminum nudiflorum)

As we progress through the month of March, our anticipation for discovering spring flowers rises. Meanwhile, a few winter-blooming plants such as Winter Jasmine must satisfy our thoughts of spring. This spreading shrub has been in bloom near the Program Shelter for the past several weeks and will continue to flower sporadically throughout March. Its bright yellow tubular flowers extend from the axils of the green, angled stems and appear before the leaves come out.

Winter Jasmine was originally imported from China to Britain in the 1840s. It provides a good ground cover, particularly on sloping ground or raised structures where it can cascade downward. It is often mistaken for Forsythia, but blooms earlier and for a longer period. It can also be readily distinguished by its green shoots and spreading habit.

Roundlobe Hepatica (Hepatica americana)

Early to Mid March

Roundlobe Hepatica is one of our earliest blooming wildflowers along Arboretum trails. Look for it in early March along the lower portions of the Cemetery Ridge Trail and somewhat later along the Oak-Hickory Trail. The flower emerges from the decomposing forest leaf litter as a bright spot of blue or white. The showy sepals (it has no petals) are subtended by green bracts. Its leaves are intermingled with the brown leaf litter and are often difficult to see. The leaf color varies from faded green to purple - the ones present now developed during the previous season and have allowed the plants to photosynthesize during the winter months. New leaves are formed after blooming.

Two species of Hepatica are found in our area. The 3 lobes of Roundlobe Hepatica are relatively shallow and rounded at the tips, while leaves of Sharplobed Hepatica (Hepatica acutiloba) are more deeply lobed and have acutely pointed tips. The genus name Hepatica is based on the resemblance of the leaf to the liver. Hepatica has been used for a variety of medicinal purposes - in the late 1800s, more than 400,000 pounds of dried leaves were used in one year to make a tonic for liver ailments.

Bloodroot (Sanguinaria canadensis)

One of the harbingers of spring at the Arboretum is Bloodroot, a member of the Poppy family. At this time, it is in full bloom in the wildflower garden adjacent to the Visitors Center; it should soon be making an appearance along the Oak-Hickory Trail and elsewhere at the Arboretum. When it emerges, the distinctive leaves are clasping the flower stalk, but shortly after emergence, they gradually open up. Typically Bloodroot flowers have 8-12 petals with the upper ones often being somewhat larger than the lower ones - some of the plants in our wildflower garden, however, have almost twice as many petals. The common name Bloodroot is based on the red-orange sap that oozes from the underground rhizome and other parts of the plant when cut. Although the plant has been used for medicinal purposes, the alkaloids in the extracts can be toxic if ingested.

Red Maple Blooms (Acer rubrum)

One of the first deciduous trees to bloom in the spring is Red Maple. As you are driving toward the Arboretum or walking along one of the trails, you can see its reddish blooms beginning to appear in the upper forest canopy. Red maple has male and female flowers that occur on separate branches of the same tree, or a tree may have only male or only female flowers. The reddish bloom comes primarily from the female flowers and the fruits as they mature. The male flowers tend to have a yellowish color. The fruits - called samaras - are similar to those of other maples in having two wings. As spring progresses, you are likely to see abundant flower parts and later numerous samaras on the ground as you walk the Arboretum trails. In the fall, the leaves contribute a brilliant red to the forest canopy.

Lenten Rose (Hellebore) (Helleborus x hybridus)

One of the earliest flowers blooming in the Wildflower Gardens around the Arboretums Visitors Center is the Lenten Rose. A member of the Buttercup Family (Ranunculaceae), the nodding flowers of the Lenten Rose have five showy white to pink sepals which may persist into the early summer. In our area, the flowers may appear as early as January and often can be found through April. The common name reflects the blooming period which occurs during the season of Lent. The dark green compound leaves, which provide a good ground cover, arise from an underground stem the plants being referred to as acaulescent (without an aboveground stem). Helleborus species are native to Europe and China. Some of these species have been extensively hybridized, and Lenten Rose, although frequently referred to as Helleborus orientalis, is generally considered to be one of these acaulescent hybrids. All parts of the plants contain toxic alkaloid compounds, and may cause a mild skin rash if handled extensively. The plant is considered to be deer-resistant, and may be planted in areas subject to heavy deer browsing to reduce damage.

Adam's Needle (Yucca filamentosa)

Several Yucca plants can be seen along the North Forest Loop Road, the new Rock Pile Lead trail, and elsewhere on the Arboretum. These plants are known as Adam’s Needle, Bear Grass, or Spanish Bayonet and most likely represent ones that were planted at or escaped from old home sites. They have sword-like pointed leaves (8-32 in. long) that radiate upward from very short woody stems at the ground surface. The margins of these fibrous leaves fray into stiff, filamentous, white threads that curl along the leaf edges. In summer Yucca produces a tall stalk (3-8 ft high) with showy, creamy white flowers. Yucca depends on a moth for pollination, while the moth requires the Yucca as a site for raising its larvae - a classical example of mutualism. The female Yucca moth collects pollen balls from the anthers of a Yucca flower which she then transfers to another flower. At the same time she deposits one or more fertilized eggs into the plant’s ovule. As the moth larva develops, it feeds upon the Yucca seeds.

Yucca belongs to the plant family Agavaceae (though some botanists assign it to the Liliaceae). There are 40-50 members of this genus, many growing in arid desert to semi-desert climates. The UT Herbarium web page lists two species of Yucca present in our area - Yucca filamentosa and Y. flaccida - both commonly called Adam’s Needle. Some botanists consider these both to be Yucca filamentosa. These species were most likely originally found along coastal areas of the Southeast but have become naturalized inland to the west and north.

Spicebush (Lindera benzoin)

Spicebush is an early blooming shrub that is found on the banks of Scarboro Creek below the Visitors Center and along several of the Arboretums trails. It is also in flower in the wildflower garden at the Visitors Center. Spicebush is dioecious (i.e., it bears male and female flowers on separate plants). When in bloom, the shrub is covered with many small yellow-greenish flowers that appear before the leaves.

Three of the Spicebush plants found in the wildflower garden have pistillate flowers while the one close to the bridge entering the Marsh area is male. The crushed leaves and twigs are aromatic, which is the basis for its common name. In the fall, the shrub bears bright red, oblong fruits which persist into the winter and provide a food source for birds.

Rue Anemone (Thalictrum thalictroides)

Late March to Early April

Numerous small white flowers are conspicuous along the Oak-Hickory Trail this week (April 5-12). Rue Anemone, or Wind Flower, belongs to the buttercup family. The basal leaves are divided into nine leaflets, each of which has three rounded lobes. The flowers are white to pinkish with several flowers being borne in an umbel - i.e., a long flower stalk with several branches originating from a common point. These plants can also be seen at a low point along the Cemetery Ridge Trail, in the same general location as the Roundlobe Hepatica seen in late March.

Other wildflowers soon to come include Mayapple (palmate leaves have emerged), Fly Poison (dark green clusters of basal leaves are particularly conspicuous along the Oak-Hickory Trail), and Violets. Red Maples have been in bloom since early March, and the red flowers parts have been, and are being, shed along the trails. The Magnolia Orchard is nearing its peak bloom, and the ground is covered with purple, red, pink, and white tepals (showy petals and sepals that are undifferentiated).

Cornelian Cherry Dogwood (Cornus mas)

Winter Jasmine (Jasminum nudiflorum)

Roundlobe Hepatica (Hepatica americana)

Bloodroot (Sanguinaria canadensis)

Red Maple Blooms (Acer rubrum)

Lenten Rose (Hellebore) (Helleborus x hybridus)

Adam's Needle (Yucca filamentosa)

Spicebush (Lindera benzoin)

Rue Anemone (Thalictrum thalictroides)