July 25th – These oak knopper galls actually took me by surprise a couple of days ago, but the photos I took weren’t great, so I revisited the saplings they’re growing on today.

I spotted them on a tree near Victoria Park in Darlaston and I don’t think there’s a single normally formed acorn on that tree at all, and yet several adjacent ones have no knoppers at all.

These mutations of normal acorns are of course caused by a tiny wasp that lays eggs in the acorn buds earlier in the year. A secretion the eggs are coated in causes the acorn bud to mutate and grow in a distorted form, forming a gall, with the wasp egg at the centre. 

The larva hatches, and eats it’s way out of the gall, which provides it enough nourishment to grow to maturity.

Insect galls like this don’t hurt the tree, but of course, do affect it’s fecundity.

Isn’t nature amazing?