If you’ve not seen one before this is a Robin’s Pincushion. Or a ‘Bedeguar Gall’.
This ‘pincushion’ in the hedgerows is a gall from a wasp that lays eggs in the stems of wild roses.
The larvae live in the rose stems during the winter and emerge in spring as a tiny gall wasp called Dipoloepis Rosa. The gall is home to 50-60 grubs and in the winter the ‘pins’ or hairs will fall off leaving a woody ball in the rose stem.
I’ve seen dozens of these this year – I can’t remember seeing quite as many in previous years but perhaps I’ve not been looking properly! You know how it is – you see one, and then another, and another…
And below is a Robin’s Pincushion in winter: