Invasive Species in Forests

The kudzu vine, pictured here growing on trees in Atlanta, Georgia, is an invasive species brought to the United States from Japan and initially planted in the South to control erosion. Photo: Scott Ehardt, Wikimedia Commons (Public Domain).

A primary goal of a forest owner is to have a healthy forest. To most forest owners, a healthy forest means healthy, living trees. Indeed, inspecting your trees regularly is important. However, to maintain a healthy, thriving forest, you must take other …

Oak Decline

Written by D.J. Moorehead and G.K. Douce for Forest Encyclopedia Network

Causal Agents

Oak decline is the name given to a slow-acting disease complex stemming from interactions between biotic and abiotic stressors of oaks (Quercus spp.). Abiotic factors that contribute to oak decline include tree maturity, low site productivity, drought, and spring frost. Biotic factors include root diseases such as Armillaria root disease (Fig. 1) (Armillaria spp.), canker causing fungi such as Hypoxylon canker (Fig. 2) …

Sudden Oak Death in the Eastern United States

  Adapted from: D.J. Moorhead and G.K. Douce for Forest Encyclopedia Network     


Sudden oak death, caused by the pathogen Phytophthora ramorum, is a potentially devastating disease. P. ramorum has been found in nurseries in California, Oregon, Washington, and British Columbia, and more recently in the eastern United States. Sudden oak death causes leaf and shoot blights in most hosts, and is known as Ramorum shoot and leaf blight in the nursery industry. In the forest the fungus can cause bole

Purple Loosestrife-Lythrum salicaria

Written by D.J. Moorhead and G.K. Douce for Forest Encyclopedia Network
Figure 1. Purple loosestrife is easily recognized in the summer and early fall by its showy spike of purple flowers. Photo by Eric Coombs, Oregon Department of Agriculture, courtesy of

Purple Loosestrife is a tall, perennial forb that can grow up to 10 feet in height. It is easily distinguished by the abundant, showy spikes of purple flowers that occur at the tops of the plants (Swearingen et …

Oriental Bittersweet-Celastrus orbiculatus

Written by D.J. Moorhead and G.K. Douce for Forest Encyclopedia Network
Figure 1. Oriental bittersweet’s leaves are elliptical in shade and alternately arranged. The vines can wrap tightly around trees, potentially girdling the tree and killing it. Photo by James H. Miller, USDA Forest Service, courtesy of

Oriental bittersweet is a deciduous, climbing, woody vine that can grow to lengths of 60 ft (Miller 2003). The alternate, elliptical leaves are light green in color (Fig. 1). Small, inconspicuous, auxiliary …

Kudzu-Pueraria montana (Lour.) Merr.

Adapted from: D.J. Moorhead and G.K. Douce for Forest Encyclopedia Network
Figure 1. Distinctive three-parted leaf of kudzu. Photo by James H. Miller, USDA Forestry service, courtesy of

Kudzu is a climbing deciduous vine capable of reach lengths of over 100 feet. The stems can grow to 4 inches in diameter and the large semi-woody roots can reach depths of 3 to 16 feet (Miller 2003). Kudzu is easily identified because it grows in a large dense mat of …

Mimosa – Albizia julibrissin

Written by D.J. Moorhead and G.K. Douce for Forest Encyclopedia Network

A mimosa infestation favors disturbed sites, where they can grow quickly and prevent native plant establishment.

Figure 1.  Mimosa flowers are very showy and fragrant. The leaves are delicate-looking and bipinnately compound.  Photo by Ted Bodner, Southern Weed Science Society. Figure 2.  Mimosa can quickly invade forest edges and old fields. The showy flowers make infestation very conspicuous.  Photo by James H. Miller, USDA Forest Service. Image credits:

Mimosa, also known as silk tree, is a small deciduous tree that is 10 to 50 feet in height, often having multiple trunks. It has delicate looking bi-pinnately compound leaves that resemble ferns (Miller 2003). The bark is smooth and light tan to greenish in color. Mimosa has very showy, …

Chestnut Blight


Written by: D. J. Moorhead, G. K. Douce, C. Evans, and D. Kennard for Forest Encyclopedia Network
Figure 1. A typical chestnut blight canker on a small

Diversity in the Forest Understory

Written by Amy Grotta

The understory of a forest is made up of the trees, shrubs, and herbaceous plants that exist below the canopy. In general, the forest understory makes up the largest percentage of plant diversity in a given forest ecosystem. While the canopy, or overstory, may be composed of one to a dozen tree species, depending on the ecosystem, many more plant species tend to be found in the understory (Table 1).

Table 1. Number of plant species …

Dogwood Anthracnose

Written by D. Kennard for Forest Encyclopedia Network
Figure 1. Stem dieback from dogwood anthracnose (Discula destructiva). Photo by Robert A. Anderson, courtesy of

Dogwood anthracnose is a relatively new disease to North America. It was first observed in 1976 affecting a population of Cornus nuttallii in Washington state (Byther and Davidson 1979). Two years later, Pirone (1980) noticed a widespread and rapid deterioration of flowering dogwoods in New York and Connecticut (Fig. 1). In 1983, the …