During late spring and summer, tubular growths up to 5 millimetres (0.20 in) long develop apically on the leaves of Tilia sp.

These galls are yellow-green or red in color, may be very numerous, and predominantly occur on the lower leaves in some sub-species.

Individually, "Eriophyes tiliae" are less than 0.2 mm long, but the chemicals it releases while drinking sap from the lower leaf epidermis have a dramatic, consistent and colourful effect.

An upright, hollow, red finger-like extension grows from the leaf around the mite.

Before the autumn, the mites, which up to now have been actively feeding and growing inside the galls, depart from these shelters and seek protected sites elsewhere on the tree.