Let’s see what species are present at Glen Echo due to their need for specific substrates. I used Jane Forsyth’s article on Geobotany to evaluate whether species found in Glen Echo match their substrate limitations proposed in Forsyth’s article.

All of the species recorded were found in an area known to limestone substrates due to glaciers removing the sandstone and shale layer.

Limestone/limy substrates:

Eastern Redbud, Cercis canadensis

Redbud bark is dark and smooth, but later can transition to a more ridged appearance as it ages. Leaves are simple in an alternate arrangement. The leaves heart-shaped with fan-like veins. The leaves are usually green, but have red coloration at the beginning of their growth. The flowers are perhaps the best identifying feature as they occur in clusters in pink to purple coloration. The flowers are rather conspicuous as they occur all over the tree including the stems and trunk. I concur with Forsyth’s assignment of this species being limited to limestone and limy substrates.

Hackberry, Celtis occidentalis

Hackberry trees are easily identified by their asymmetrical leaves that are uneven at the base and course to touch. The leaves are alternate with distinct teeth. The bark is cork-like with wart-like protuberances. The slim trunk supports this medium-sized tree to heights of 50 feet. I concur with Forsyth’s assignment of this species being restricted to limestone and limy substrates.

High-lime/clay-rich substrates:

Sugar Maple, Acer saccharum

Bark of the sugar maple is grayish brown with long fissures that are irregular in shape. This tree is one larger maples, as it is known to grow to 100 feet and taller. The leaves are simple and lobed into 5 parts. Sinuses are rounded between lobes. I concur with Forsyth’s assessment of these trees being restricted to substrates of high-lime and clay-rich values.

White Oak, Quercus alba

White oaks are considered large trees with branches that starkly exit the trunk not far above the base. The bark is rarely white like the name might assume, but rather grey to light grey. Leaves are a dark glossy green with shallow lobes. Lobes are blunted instead of pointed as seen in the red oak group. I concur with Forsyth’s assessment that these trees require soils with high-lime and clay-rich values.