The Knobs are divided into two sections (East Knobs and West Knobs) on the Walk Across Kentucky, and are located on the northern border of Alumni Drive on either side of The Arboretum entrance drive.  Perhaps confusingly, the Eastern Knobs occur to the west, and the Western Knobs to the east.  This layout was necessary so that the Eastern Knobs border the Appalachian Plateau and the Western Knobs border the Pennyrile collection, just as they do naturally in Kentucky.

The Eastern Knobs display the transition between The Bluegrass and the Appalachian Plateau, and thus plant species indicative of both those regions are found here, including Kentucky coffeetree, fringe tree, red oak, snowberry, and gray dogwood.  Part of the Eastern Knobs is located in a particularly wet area where winterberry holly, giant cane, and willows predominate.  This region also contains the largest grove of tulip trees at The Arboretum.

The Western Knobs naturally transition between The Bluegrass and Pennyrile, though at The Arboretum they only border the latter.  Here, some smaller examples of prairie remnants exist between gaps in the oak trees which dominate the overstory, including overcup oak and chestnut oak.  A wetter section of the Western Knobs contains hop-hornbeam, willow, river birch and bald cypress.

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

 “The Knobs region is a complex of broad floodplains, terraces, foothills, erosional remnants (‘knobs’), and escarpments that are transitional from the Bluegrass to surrounding higher plateaus.  Although the region’s width ranges from about 30 miles, to only 10 miles in some southern sections, its characteristic knobby hills are easily recognized as one travels east, south or west from the Bluegrass.  These hills contain a series of younger rocks, mostly laid down during the Silurian age (ca. 410-440 million years ago), Devonian age (360-410 mya), and Mississippian age (330-360 mya).

This region has a great variety of natural vegetation, reflecting the variety of rock types and topographic positions.  At the wet extreme, swampy forests, more extensive than anywhere else in central or eastern Kentucky, developed on the bottomlands between the hills themselves.  These are often poorly drained, due to dense clay and fragipan layers as well as their low topographic position.  At the dry extremes, especially on rocky soils and south facing slopes, open woods, grasslands, and rocky ‘glades’ were maintained, often with unusual wildflowers.”