Restoring native flora to the natural areas in the Arboretum will create many opportunities to show the value of biodiversity.


Source: Michael Hassler
Leaves of Quercus alba (white oak), the dominant native tree in the Hartley Wood.




Source: Joel McNeal
Wild columbine (Aquilegia canadensis), which grows in rich, rocky woods, slopes, cliffs, ledges, pastures, and roadside banks, was found in the Hartley Wood during the 2001 floristic inventory of the Arboretum.



Arboretum Launches Woodland Restoration Corps


Exotic species such as privet and honeysuckle are becoming the dominant species in
the understory of the Arboretum's Hartley Woodlot.

On March 25, 2007, fifteen volunteers joined Dr. Kim Steiner, the Arboretum director, Samuel Grinstead, research assistant, and Sarah Melissa Witiak, post-doctoral scholar, for the inaugural work session of the Arboretum Woodland Restoration Corps (AWRC).

Source: Michael Hassler
Smooth blue aster (Aster laevis) is one of the woodland herbs whose habitat is disappearing as nonnative species such as garlic-mustard carpet the forest floor.

The corps will focus its first efforts on controlling the invasive, exotic shrubs that are crowding out native species in the understory of the Arboretum's Hartley Wood, a popular destination for hikers, bird-watchers, and naturalists that is contiguous with Sunset Park in the College Heights development of State College, Pennsylvania.

The outline of the woodlot showing plot locations and density of invasive plant species. The plot centers are represented by the grid of points.

Their work is being guided by Mr. Grinstead, who has developed a woodland restoration plan for the woodlot, and Ms. Witiak, who is a volunteer coordinator for the corps.

At an orientation meeting on March 22, Mr. Grinstead explained to potential volunteers that this 42-acre parcel is a valuable ecological site. Although there are native pine and hickory trees growing in the woodlot, seventy-five percent of the larger native trees are oaks (62 percent white oak, 13 percent black oak), some of which are more than 200 years old. The stand of oaks that forms the majority of the forest canopy is, therefore, a remnant of the typical upland oak forest that grew here before Europeans arrived.

Because the surrounding land was first farmed, and then developed as State College and the University expanded, this woodlot is one of the few remaining natural areas in an urbanizing landscape. Its tall oaks provide habitat for a variety of native woodland herbs, ferns, and shrubs, and for wildlife, including Baltimore orioles, scarlet tanagers, ovenbirds, and rose-breasted grosbeaks. Unfortunately, shrubs such as privet and honeysuckle, and nonnative trees such as Norway maple and mazzard cherry, have migrated into the interior of the woodlot and are crowding out most of the oak seedlings.

To restore the natural condition of the woodlot, corps members are being trained to identify and remove the following invasive species:

  • Barberry (Berberis spp. DC.)
  • Bush honeysuckles (Lonicera spp. L.)
  • European buckthorn (Rhamnus cathartica L.)
  • Garlic-mustard (Alliaria petiolata [M. Bieb.] Cavara & Grande)
  • Japanese honeysuckle (Lonicera japonica Thumb.)
  • Mazzard cherry (Prunus avium L.)
  • Multiflora rose (Rosa multiflora L.)
  • Norway maple (Acer platanoides L.)
  • Oriental bittersweet (Celastrus orbiculatus Thumb.)
  • Privet (Ligustrum spp. L.)
  • Russian and autumn olives (Elaeagnus spp.)

Volunteers include members of the community, the University's student body, Penn State's Master Gardener program, and several groups on campus, including Eco-Action, the Penn State Student Chapter of the Society of American Foresters, the Xi Sigma Pi honorary forestry fraternity, and the Wildlife Society. In three work sessions, they have already removed dense thickets from approximately one-half acre along the edge of the woodlot.

After the woodland restoration corps had cleared exotic shrubs from the plots along the woods' edge, only a few native trees and shrubs remained. The next step is to monitor the area to prevent reemergence of the nonnative species.

Because controlling exotic species in the woodlot will be a long-term process, there will be an ongoing need for volunteers. Ms. Witiak plans to schedule monthly work sessions of three to four hours each through October, and to resume the sessions in March 2008. Eventually, teams will be formed to monitor the cleared plots for signs of reemerging exotic species. Where native flora do not reestablish themselves, the corps will propagate and plant native species that are indigenous to central Pennsylvania.

The Arboretum is grateful to those who have helped us to take the first steps in preserving and restoring this old-growth forest, and we hope that many more decide to join. Volunteers are welcome to participate in one or more work sessions.

To learn about future work sessions, please write to Kate Reeder, Arboretum program assistant, at



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