Elm tree with buttress roots in Schenley Park, 21 April 2018 (photo by Kate St. John)

14 April 2026

Most trees in western Pennsylvania have trunks that taper gradually from the ground to the first large branches. Some have a few lumpy above-ground roots but our tree trunks generally look like the white oak at left below.

Buttress roots — the vertical flanges on the tree at top — are so unusual in Pittsburgh that I take photos of them. In this case it’s an American elm in Schenley Park.

Base of a white oak and an American elm in Schenley Park (photos by Kate St. John)

In some habitats buttress roots are normal, such as on bald cypresses in swamps …

Bald cypress buttress roots and “knees” at First Landing State Park, Virginia, Nov 2015 (photo by Kate St. John)

… and tropical trees like this one in Panama.

p.s. The name for these root structures comes from the buttresses, best seen in Gothic architecture, that hold up tall heavy walls and high vaulted ceilings. The walls would collapse outward without the added support.

The buttresses on Heinz Chapel are so beautiful that we take them for granted. There are at least three in this photo.

Buttresses on Heinz Chapel, Univ of Pittsburgh (photo from Wikimedia Commons), mark up to note buttress