This is not exactly a gardening question, but maybe someone here will know: what is capable of causing large galls on henbit (Lamium amplexicaule)? I have a lawn that I keep on the long side and never treat with weed killers, so I get plenty of henbit that flowers this time of year. Only this year many of the henbit plants are bearing a bizarre gall that I've never seen on them before. The galls are greenish, up to 1 cm or more in diameter, and sometimes more than one are fused together, on the stalks under the leaves. When cut open, they have an internal structure something like that of small cucurbits or gourds.
Anyone know what this might be?