Identifying Green Growths on Littleleaf Linden Leaves

A littleleaf linden has green, worm-like growths standing upright on leaves—some leaves have few, others many. The owner wonders if they're insects or something else.

Two Likely Causes

1. Insects (Mobile)

If they move when touched, they're likely caterpillars or larvae. Leaves usually show chewing damage. Treat with liquid carbaryl (Sevin) sprayed on foliage.

2. Leaf Galls (Immobile)

If fixed to the leaf, they're galls caused by tiny wasps laying eggs. The wasp secretes chemicals that force leaf cells to expand around the egg. Galls come in many shapes—spikes, bumps, blisters. They cause no health issues and need no treatment.

Expert Lean

The description strongly suggests galls. A photo would confirm. If galls, simply monitor; the tree will be fine.