Forest
Stewardship News Release
July
27, 2005- For Immediate Release
Contact: Allyson
Muth , Phone: 814-863-0401 E-mail: abm173@psu.edu
Ferns: the Beautiful, the Good, the Bad
Written by: Jim Finley, 814-863-0401, fj4@psu.edu
Ferns are common to Pennsylvania. On a summer day, driving through nearly any forested area in the Commonwealth ferns will be a visible and common component of the plant community. For some folks, a forest without ferns is incomplete. We have come to expect to see ferns in our forests. Ferns are summer. They are the green on the forest floor. Walking through the forest, ferns trampled under foot impart a special "green" smell to the summer air.
Ferns, while delightful to see and smell, are not always a sign of forest health. In Pennsylvania, we have at least 60 species of ferns, some large - up to 6 foot tall - and some very small - only inches tall. Some ferns, such as ostrich, sword, Christmas, interrupted, cinnamon, and spinulose woodfern, occur in specific habitats and appear as "clumps" of fronds. The clump ferns spread principally by casting spores that move on the wind. Under the right conditions, the spores germinate and develop eventually into adults. Because of their specific site requirements and the chance mating of spores with soil and moisture conditions, the spread of these ferns is slow.
Some of these fern species provide food and shelter for some wildlife species. Woodfern, Christmas, and at least some of the other clump provide food for deer, turkey, and grouse. In fact, at some times of the year, the green foliage of these ferns is principal components of grouse diets.
The other type of fern, the individual frond ferns, has two mechanisms for spreading. Like other ferns, they produce spores and face the same trials as all ferns. These ferns also spread by sending out specialized root like structures called rhizomes. These rhizomes spread under the forest litter and periodically support a frond creating a spreading mat of foliage with fronds several inches apart. Under the right light conditions, the spread of hayscented, New York, and bracken ferns across a forest floor is rapid and a threat to forest development. These three fern species are rather common in the state, and these three species are a bane to forests. Seldom does any wildlife feed upon the single frond ferns, which helps explain their increasing occurrence in our state's forests. There is ample evidence that deer, by selective feeding remove plants that would compete with problem ferns. The simple removal of other understory plants and the suppression of tree seedlings by deer foster the spread of single frond ferns.
Once the forest floor becomes a sea of green hayscented, bracken, or New York ferns our ability to manage forests changes. These ferns create low shade. This shade is very dense, too dense for some tree and most other plants to receive enough light to germinate. If other plants do germinate, the quality of the light that filters through the fronds changes, the red and blue light critical to seedling growth and development is taken up by the fronds. Only the green light, reflected by the fronds reaches the soil surface. Finally, overtime the fern community, which dies back each fall, creates a thick mat of fronds and rhizomes, a litter layer that decays slowly. Other plant seedlings that germinate in this mat often die from a lack of moisture.
Forests with ferns are pretty to view. Unfortunately, the presence of ferns reduces the chances for other plants such as wildflowers, native shrubs, and forest trees to grow. Once established, the understory of ferns will persist and change the forest for years to come. Reducing or excluding deer will help slow the spread of ferns, but it will not necessarily permit other plants to compete successfully with the ferns. Research suggests that we will have to use herbicides to reduce fern competition for light if we are to reestablish some forest functions.
Before you harvest trees or when you plan management activities, contact your forester to get advice about ferns and forest renewal. If you are a hiker or casual forest observer, enjoy the ferns, but know that they are affecting important forest functions and do not indicate an ecologically healthy forest.
If you would like to know more about forests and ferns, call the Forest Resources Extension Office and request the Winter 2004 Forest Science Review, titled "The Forest Nobody Knows," published by the USDA Forest Service, Northeastern Research Station (see contact information below).
The Pennsylvania Forest Stewardship Program provides publications on a variety of topics related to woodland management for private landowners. For a list of free publications, call 1-800-235-WISE (toll-free), send e-mail to , or write to: Forest Stewardship Program, Forest Resources Extension, The Pennsylvania State University, 320 Forest Resources Building, University Park, PA 16802. The Pennsylvania Bureau of Forestry and USDA Forest Service, in partnership with the Penn State's Forest Resources Extension, sponsor the Forest Stewardship Program in Pennsylvania.
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