1993 Proceedings of the Midwest Oak Savanna Conferences

REMOVAL OF EUROPEAN BUCKTHORN AT THE GROVE NATIONAL HISTORIC LANDMARK

A history of fire suppression has resulted in closure of the Grove's open oak-dominated, savanna canopy. As a result, a noticeable decline in the richness of the native vascular flora has occurred. European buckthorn (Rhamnus catharticus) has become widespread, contributing to the decline. Management of the site over the last ten years includes use of mechanical equipment, herbiciding, and prescribed burning by trained personnel. These techniques have slowed the invasion of buckthorn and led to a spectacular regeneration of oaks.

INTRODUCTION 

Ten years ago (1983), a systematic approach to removal of European buckthorn (Rhamnus catharticus) was begun at The Grove National Historic Landmark, a special facility of the Glenview Park District. Prior to the District's acquisition of the Grove site in 1976, two, small-scale attempts were made to remove European buckthorn by cutting and grubbing of the roots. Each labor-intensive attempt was soon abandoned.

Since the early 1920s, fire suppression has resulted in closure of the historically, open oak-dominated savanna. The closed understory canopy prevented oak seedlings from being established. Thickets of European buckthorn dominated the understory, invading with such permanence that they spaced themselves approximately 10 to 25 feet apart. These patterned thickets not only prohibited forest tree species regeneration, they subjugated and eventually obliterated understory shrubs and herbaceous plants associated with the bur oak forest type.

In 1983, the Grove began to cut large thickets of buckthorn. All buckthorn with a basal diameter in excess of 2.5 cm were cut and processed through a wood chipper (the chips were utilized for trail top dressings.) Cut stumps were treated with Bush Killer (ORTHO B). Application of this herbicide at 100% concentration did not provide a satisfactory kill rate of the cut buckthorn.

At the same time, prescribed burning of the extant savanna and woodlands was begun. Seed collection from the Grove site was initiated and dispersal of seeds took place after fall burns.

Early attempts to utilize fire in the process of restoration were met with skepticism by the Glenview Park District and the local fire department. A common question asked with alarm was: You're going to control exotic species with a forest fire?

It was time to build support for prescribed burning. Historical data on fire frequency in oak woods was gathered. Reports and press releases were prepared. Staff attended burn school. Coordination with the fire department was established. Prescribed burn policies and procedures were drafted. An effort to educate and inform the public was carried out.

As the years rolled by, a systematic approach to controlling European buckthorn evolved. As we gained experience, refined reforestation techniques, and applied our imaginations, the process progressed as follows:

EXPERIENCE

We began our prescribed burns after attending a series of burn schools, practice burns and fire department coordination meetings. Equipped with drip torches, water pumps, flappers, rakes, trucks with pumps and tanks, fire hydrant hoses, and lots of people power, we were prepared. Our first fires were six inches high and produced spotty, smokey burns.

Today, armed with the proper EPA permits, we load a wheelbarrow with Indian pumps and flappers, employ three or four people with drip torches, and burn ten times the acreage in one day as we used to burn in a week. All personnel have radios to communicate with our office. Local authorities are notified prior to a burn. We have established credibility with the fire department.

TECHNIQUES 

The transition from labor intensive removal of European buckthorn to mechanical removal and chemical treatment has allowed for large-scale restoration at reasonable expense to the Glenview Park District. In the beginning, buckthorn was removed with axes, a beat up chain saw, and grubbing axes. Now small chain saws (throwaways), tractor-mounted modified woods mowers, and herbicides are utilized. Originally, effective chemicals were not used, resulting in intense resprouting. Today, Garlon 4 is applied yielding a 100% kill rate. All personnel who apply Garlon hold applicator licenses. Blue dye is added to the Garlon to insure all stumps are treated. We now use less personnel and remove more European buckthorn through investments in tools, use of mechanical apparatus, and increased training than we accomplished with a larger, untrained staff.

IMAGINATION 

Formerly, cut buckthorn was utilized in many ways. Trails were wood chipped, fences constructed, logs processed for firewood, and projects with school groups initiated. Large brush piles were also burned. Now buckthorn is left where it falls. Heavy snow compresses it. Fire consumes it. In a couple of years it becomes almost invisible in the savanna grasses.

Removing buckthorn opened up the forest floor to easy grazing access by white-tailed deer (Odocoileus virginianus). By leaving the buckthorn where it falls, deer are kept from browsing on desirable plants. Although this is a stop-gap measure, it coincides with our deer removal program.

In conclusion, we place a high value on mechanical and chemical techniques to remove European buckthorn, solid training of personnel, and the use of prescribed burning. As a result, the Grove's savannas continue to expand and flourish. The swell and swale of the landscape is visible, and much of the savanna plant community is again nurtured by fire and bathed in sunlight.