The Bluegrass region is the largest of any on the Walk Across Kentucky, partly because The Arboretum is located at the heart of the Bluegrass and we have the soils and environmental conditions most conducive for cultivating the unique (and often imperiled) flora of the region.  The Bluegrass region also acts as a buffer to The Arboretum Woods, a 15 acre forest often cited as one of the last remaining examples of inner-bluegrass woodlands.   The Woods is highly diverse for such a small and fragmented urban forest, but is an ecosystem threatened by the encroachment of invasive exotic species that escape from horticultural plantings.  Bush/Amur honeysuckle, Japanese honeysuckle, purple wintercreeper, burning bush, privet, callery pear, and Oriental bittersweet are particularly troublesome exotic species that threaten forest health, and efforts are ongoing to remove these invaders.

Other sections of the Walk Across Kentucky Bluegrass collection highlight some of the distinctive physiography of the region.  Large slabs of limestone can be found scattered amongst both woodland and open areas, sometimes with rock-outcropping species like prickly pear cactus and false aloe.  Bur oak and chinquapin oak are typical of this region and are widely represented.  Blue ash, white ash, suger/black maple, and the Ohio buckeye are the other widely planted tree species.  More unusual woody plants hidden in the Bluegrass include prickly ash and wafer ash (both of which are actually in the citrus family, as well as yellowwood, chokecherry, and wahoo.  The Arboretum’s largest cane-break, a big stand of the giant native cane, is also found in the Bluegrass.  Other noteworthy exhibits here include the oak/ash savannah, Eden trace, and the Bluegrass rainwater garden.

From ‘The Big Picture: Ecological Regions of Kentucky’ by Dr. Julian Campbell:

 “Many millions of years ago, the Bluegrass Region was pushed up by forces within the earth’s crust, exposing a ‘dome’ of bedrock that is older than anywhere else at the states surface.  These limestones and calcareous shales were deposited 440-450 million years ago (in the Ordovician age), and are teeming with fossils of various shellfish and coral-like organisms.  These rocks have weathered to produce some of the most fertile upland soils in North America, with a particularly high phosphate content in some karst plains, though less so in hilly sections with more shale and recent glacial deposits.

The native forests, especially on more fertile soils, are distinct from all other regions.  Characteristic trees include black maple, bitternut hickory, Ohio buckeye, Kentucky coffee tree, hackberry, black walnut, ashes (blue, white, green), and oaks (chinquapin, bur, shumard, northern red, etc.).  The ‘rich herbage’ and salt springs or ‘licks’ in this region have attracted large populations of various grazing animals throughout the ages.  Mastodons, mammoths and other extinct species roamed these plains as the last ice age waned, leaving concentrations of bones at some of the larger licks.”

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