Horned Oak Gall

The “horns” that give the Horned Oak Gall its common name are popping through the surface of the galls in southwest Ohio. The horns are just the tip of the iceberg with this gall-making wasp. They also produce leaf galls.

The “horns” that give the Horned Oak Gall its common name are bursting to the surface in southwest Ohio. The horns make the galls look like a miniature version of a medieval martial arts weapon. The woody stem galls were formed under the direction of the gall-wasp, Callirhytis quercuscornigera (syn. Callirhytis cornigera (Family Cynipidae)).

The “horns” that give the horned oak gall its common name are rising to the surface in southwest Ohio. The woody stem galls were formed under the direction of the gall-wasp, Callirhytis cornigera (Family Cynipidae) to feed and house immature grub-like wasps.

The emergence of the "horns" that give horned oak galls their common name is a short-lived event. I've commonly observed fully extended horns, but seeing them in the process of breaking through the gall surface is a rare treat and it's happening right now in southwest Ohio.

Spring marches forward at the Secrest Arboretum of the OSU Wooster Campus. Enjoy the river birches, the fungal and insect galls, and the marcescent beech leaves and watch for more developments soon as Growing Degree Day accumulate.

The physical emergence of the "horns" that give horned oak galls their common name is such a short-lived event I've only witnessed it one other time in 26 years. I've commonly observed fully extended horns, but seeing them in the process of breaking through the gall surface is a rare treat and it's happening right now in southwest Ohio.

When most people think of horned oak galls, they visualize the gnarled, woody stem galls that form on the twigs and small branches of pin oaks.  This is understandable since the gall-making wasp, Callirhytis cornigera (Family Cynipidae) that's responsible for directing the growth of the stem galls spends 33 months developing inside individual chambers within these very obvious galls.

The galls grow larger in size with each season.  In early spring, as the immature wasps near the completion of their development, the whitish-tan, cone-shaped “horns” that give this gall its...