[3] The all-female generation produces galls in summer that are flat and circular with scalloped edges.

Attached to the underside of leaves, these galls are initially green, then yellow, and fade to brown.

[4] They are 7–9 mm in diameter and have a single larval chamber.

[3] The bisexual generation's galls were thought by scientist Alfred Kinsey in 1922 to belong to a new species, Andricus pedicellatus.

These galls consist of a pointed capsule at the end of a hair-like stem.