Ohio Geobotany

Ohio can be split into two defined areas of differing geological makeup. Western Ohio is characterized by eroding limestone and underlying dolomite. These eroding rocks have created a fairly flat landscape. Eastern Ohio is made up of erosion resistant sandstone and underneath, eroding shale. This creates deep valleys where the sides of hills are sandstone.

This split geology comes from a 200 million year old arch made of layered sandstone, shale, and limestone. Erosion cut into the crest of the arch, exposing the older limestone in Western Ohio and the younger sandstone in Eastern Ohio. The Teays River flowed in Ohio for about 200 million years and contributed to much of the erosion of the rock layers, namely the western limestone and the eastern shale and limestone. The river was eventually stopped by glaciers.

In Eastern Ohio, the steep sandstone-sided hills stopped the march of the Pleistocene glaciers. The glacial boundary extends south in Western Ohio but is limited to Canton in Eastern Ohio.


Glacial till is a mixture of sand, silt, clay, and boulders deposited by glaciers. In Western Ohio, the glacial till contains a lot of lime and clay due to the erosion of the limestone by the glaciers. In Eastern Ohio, the glacial till doesn’t contain much lime or clay.

Therefore, the plants that grow in Western Ohio are generally lime-loving while eastern plants prefer more acidic growing conditions. Western Ohio substrate is typically impermeable with bad aeration and drainage, but is nutrient-rich. Eastern Ohio substrate is low in nutrients and is also impermeable.

Some trees and shrubs that are usually found in substrates high in lime/limestone include eastern hophornbeam, blue ash, chinquapin oak, fragrant sumac, and hackberry.



Eastern Hophornbeam – Ostrya virginiana







The leaves of the eastern hophornbeam are asymmetrical at the base. This tree has extremely dense and hard wood. Its catkins resemble hops, hence the name.


Blue Ash – Fraxinus quadrangulata








Blue ash has 4-angled stems reminiscent of the mint family and its fruits are samaras, like other ashes. The emerald ash borer weakens ash trees.


Chinquapin Oak – Quercus muehlenbergii










Chinquapin oak is a member of the oak family. It is monoecious and produces acorns like other oaks. Its acorns are the sweetest of any oak species.


Fragrant Sumac –Rhus aromatica










As its name implies, fragrant sumac gives off a pleasant lemon smell when its leaves are snapped. Fragrant sumac is frequently confused with poison ivy, but an easy way to tell the difference is that poison ivy has white berries and fragrant sumac has red berries.


Hackberry – Celtis occidentalis








Hackberry trees are hardy and can tolerate tough conditions. The leaves are asymmetrical at the base and are prone to forming galls. Hackberries are apparently safe and delicious to eat.


Some species of trees/shrubs that are generally limited to the high-lime, clay-rich substrates of western Ohio include sugar maple, beech, red oak, white oak, and shagbark hickory. Chestnut oak, sourwood, scrub pine, pitch pine, and hemlock are generally limited to the sandstone hills of eastern Ohio.

Hemlock and sweet buckeye are both found in eastern Ohio because they both enjoy the sandstone substrate, but sweet buckeye’s range does not extend north past the glacial boundary while hemlock’s does. Hemlock thrives in cool, moist ravines, which are found north of the boundary and seem to outweigh the effects of the limestone. Rhododendron is a plant that migrated into south-central Ohio by way of the Teays River system in pre-glacial times. Its range stopped expanding in Ohio when the glaciers blocked the river.

Cedar Bog

Cedar Bog is not a bog, it’s a fen. Bogs are swampy areas with no drainage! Cedar Bog is a fen created when glaciers scraped away layers of rock, leaving behind permeable limestone. Flowing alkaline water runs over the surface and the fen flushes water away.

At Cedar Bog, I was tasked with finding two rare or unique plants. Here they are:

Oval Lady’s Tresses – Spiranthes ovalis










Lady’s tresses are a distinctive genus of orchids with tiny spiraling flowers. This particular species of lady’s tresses, Spiranthes ovalis, can be identified by its double spiral and its tiny stature. Each flower has 6 white tepals. Lady’s tresses are somewhat rare in Ohio and a prized flower of Cedar Bog.


Round-leaved Sundew








Round-leaved sundew is not rare so much as it is unique. As a carnivorous plant native to fens, bogs, and marshes, sundew catches small insects and dissolves them to extract nutrients. I love carnivorous plants, so this was my favorite sighting of the trip! Round-leaf sundew can be identified by the red “hairs” on its green and red leaves and the sticky dew that tips each hair. It has rounder leaves than the similar species Oblong-leaved sundew.