Q: We have an older Witch Hazel (yellow bloomer) that we transplanted a few years ago. The first and third growing season we’ve found these wierd green and pink growths on the leaves. There appears to be a hole in the back of the leaf, as if something burrowed into it, sometimes along the main vein of the leaf and sometimes in other spots along the leaf. They appear with the flushing out of the leaves in spring and stays throughout the season, until the leaves fall off. Occasionally we have seen carpenter ants on the branches. Can you help me?

A: The growths are actually insect galls. A mother aphid laid her eggs on the leaf tissue in April and the leaf produced a gall to protect the babies. As they grow, the aphids suck a tremendous amount of plant sap in order to extract proteins. They excrete the sticky sap, called honeydew. That’s why you see ants on the branches.

Although the galls are odd-looking, they do little harm to your plants. You can leave them be or pick them off – your choice.

See also:
The Weird Life of Witchhazel Aphids