Frederick County contains some very fertile and productive ground, especially the western part of the county that lies on the productive greenstone bedrock. Some of these sites are so prolific that nearly every plant would develop to its fullest potential if it were planted there. The forests growing in these fertile areas tend to contain a wide variety of trees, shrubs, and herbaceous material. These plants tend to grow fast and become very tall. Forests growing under optimal conditions are often called “mixed hardwood associations” due to the wide variety of trees present. Some of the more common trees found in a mixed hardwood forest include tulip poplar, red and white oak, white ash, shagbark and pignut hickory, black walnut, red and sugar maple, beech, butternut, big-tooth aspen, and white pine. Just as native plants do well here, nonnative invasive plants thrive in these areas, as well. Unfortunately, it is often the more productive forests that have the most trouble with species such as barberry, autumn olive, bush honeysuckle, tree of heaven, mile-a-minute, and stilt grass. Barberry, in particular, seems to thrive under these optimal conditions. Sometimes this aggressive exotic plant can take over most of the understory. In addition, sometimes native plants like spicebush and pawpaw exhibit invasive characteristics when they grow on these very fertile sites.
Mixed forest stands are generally found in the lower sloped sections of mountains, in terraces, and in upland hollows and coves. Sometimes tulip poplar is the dominant tree found here, forming nearly pure associations, as if it were planted here. A forestry term used to describe site productivity is “site index.” Site index is the height that a tree will grow in a certain time frame, usually 50 years. A fairly productive site in Frederick County may have a site index of 80, meaning that a given tree would be 80 feet tall in 50 years. In the productive Mixed Forest conditions, site indexes of 80 – 130 have been recorded. The 130 site index was recorded for tulip poplar growing at the base of South Mountain near Burkittsville.
Article by FCFCDB member
Nature Note for 12/17/2017