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  • Evidence for an Arboretum as a Point Source of Exotic Invasive Plants in Cincinnati, Ohio
  • Denis G. Conover (bio), Olivia M. Canterbury (bio), and Samantha A. Al-Bayer (bio)

Invasive alien plant species are a form of biological pollution resulting in the loss of native biodiversity (Gratzfeld 2016). Next to landscape alteration, the next most serious threat to our native flora is the presence of exotic species (Homoya 2012). The effort to control exotic plant species in natural areas is at great expense, both monetarily and timewise resulting in much collateral damage to native plants, wildlife and humans caused by the extensive use of herbicides and mechanical equipment (DiCicco 2014, Conover and Bergstein 2022). The primary pathway for invasive alien plant introductions is ornamental horticulture (Hulme et al. 2018). Botanical gardens, including arboretums, provide some of the best documented cases of biological invasions (Mack 2005).

Spring Grove Cemetery was established near Cincinnati, Ohio in 1845 by members of the Cincinnati Horticulture Society (Nuxhall 2009). By 1850, horticulturists had listed 4,300 ornamental plant varieties at Spring Grove Cemetery and a stock of 11,300 nursery plants (Linden 1995). "Arboretum" was added to the title in 1987, and Spring Grove Cemetery and Arboretum (SGCA) currently holds arboretum accreditation at ArbNet Level III, which requires at least 500 species of woody plants. In their plant collection booklets SGCA now boasts 1,200 species of trees, shrubs, vines and other plants (Spring Grove Woody Plant Collection 2008 and 2012). Some of these plants are native, such as a Quercus alba (white oak) in section 101 which is over 400 years old, but many are intentionally planted exotic species introduced from Asia and Europe, including a state record Phellodendron amurense (Amur cork) in section 95 (Figure 1). Unfortunately, a great many of these non-native species which have been deliberately planted at SGCA over the years have escaped from cultivation and have invaded surrounding wooded natural areas (Vincent and Cusick 1998, Conover and Bergstein 2022). [End Page 160]

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Figure 1.

Amur cork tree planted at Spring Grove Cemetery and Arboretum.

The SGCA area currently has 297 ha. About 162 ha of this area are horticulturally landscaped. In the central part of the 162 ha of the developed part of the cemetery there is a 4-ha wooded area known as the "Woodland Preserve," which is meant to be kept in a natural state with no graves. North and west of the developed part of the cemetery there are over 121 ha of woods, creeks, wetlands and open areas which belong to SGCA. In very close proximity to the SGCA property there are several natural areas owned by Cincinnati Parks, including Parker Woods, Buttercup Valley, LaBoiteaux Woods, and Salway Park which is adjacent to the banks of the Mill Creek.

In a previous study, as a follow up to botanical surveys conducted in the Cincinnati area by Thomas Lea (1849) and E. Lucy Braun (1934), the occurrence of non-native invasive plants in wooded natural areas in southwestern Ohio was documented (Conover and Bergstein 2022). Coincidentally, E. Lucy Braun and Thomas Lea are both buried at SGCA. In this current study we are focusing on plants which are known to have been planted in developed portions of SGCA which have escaped and now occur spontaneously in adjacent undeveloped areas.

In this study we have collected specimens of non-native species from the landscaped portions of SGCA which were purposefully planted there. In addition, we have collected

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Table 1.

Some of the non-native species planted at Spring Grove Cemetery and Arboretum which have invaded natural wooded areas in the vicinity (Spring Grove Woody Plant Collection Booklet 2008 and 2012).

these same non-native species from undeveloped portions of SGCA where they were not deliberately planted, but to which they have spread. The plant specimens that we have collected from developed and undeveloped portions of SGCA have been deposited in the Margaret H. Fulford Herbarium at the University of Cincinnati.

Due to efficient seed dispersal mechanisms involving birds, mammals, wind and water these exotic plants which have been planted at SGCA over...