Appendix L
Maintenance Level Guidelines
PLANT SPECIFIC CONTROL METHODS Buckthorn
Characteristics Common buckthorn (Rhamnus cathartica) and its relative glossy buckthorn (Rhamnus frangula) are serious invaders. They commonly invade hedge rows of open fields, from which they spread throughout a whole field. Both common and glossy buckthorns are small trees or shrubs that can reach a height of 20-25 feet. Buckthorn most often grows as a shrub, where it may send out several shoots. Identification “Scratching the surface” is a good way of ensuring that one has a buckthorn plant. The outer bark is dark gray or brown, and when cut the inner bark is brown, red, or orange. Buckthorn has separate male and female plants; the latter are often easy to recognize because they produce copious amounts of deep purple berries. It is especially important to remove the berry-producing plants, because they will otherwise be a constant source of infection for the area. Status Buckthorn is of Eurasian origin and was introduced in North America as an ornamental. It was planted for hedge rows in Wisconsin as early as 1849. Despite its insidious nature, it is still legally sold in the state as an ornamental. It has become naturalized and has spread over most of the southern and eastern parts of the state. Buckthorn is an especially troublesome invader of natural oak savanna and oak woodland areas of southwestern Wisconsin. Spread Many bird species relish buckthorn berries. However, the berries contain a chemical which acts as a laxative (hence the species name cathartica). The defecation by the birds insures the spread of the seeds through the habitat. Since female trees may produce abundant fruit, within a few years there can be thousands of buckthorn seedlings in the area of a mature tree. Buckthorn seeds are able to remain alive in the soil for years, and new seedlings will continue to appear for years after the plants have been removed from an area. Buckthorn threats • Destroys wildlife habitat • Replaces native vegetation • Forms an impenetrable understory layer • Causes long-term decline of a forest by preventing the growth of native tree seedlings Control Early identification, before seed production has started, is vital. Small buckthorn seedlings can be readily removed by hand. Although effective, mechanical removal disturbs the soil and encourages
12
462 Naperville Park District | 2023 MASTER PLAN
Made with FlippingBook - Share PDF online