Looks like you are the possessor of a hairy gall of some sort. These are stimulated by the larvae of a small wasp or midge simply put. If you are curious about this, remove the gall and take a one edged razor blade and slowly slice through the gall layer by layer. Close to the center you will find a small chamber with the larvae or pupa in it. When the adult emerges it will chew its way out. I will avoid the biochemistry involved in gall stimulation though it is a very fascinating subject.

Called robin's pincushion and, as Loosestrife says, its a gall caused by Diplolepis rosae, a gall wasp. You may get only one flower affected or a fair number in one year, and none at all next year. Much more common on 'wild' roses - doesn't harm the plant, but you can prune out the affected parts for aesthetic reasons if you want. If you inspect the plant, you may also find roughly spherical galls up to 60mm across on stems.

Wow! How fascinating! I thought it might be made by an insect or some kind but wasn't sure. Might take one off and dissect with my two boys. It never fails to amaze me the things you can discover and learn about in your back garden. Thank you both for sharing your wisdom.

Save one or two and cut in autumn, once the mossy yellowish covering dries up - the inner core will be full of grubs which will overwinter before pupating in the spring. You can even leave one longer and see the pupate stage later in spring next year. As a note of interest, this is the first time I've seen a yellow coloured pincushion - the reddish ones seem to be more common.

Amsterdam, the amount and variety of life that can be found in just one cubic foot of ones garden is staggering indeed.

Aye, its true - a horticultural person in a programme about soil on the tv the other day made the comment that under his feet, on the grass where he was standing, were a million life forms, just in that part... most of it microscopic, of course.

Bamboo - could the colour have something to do with where I am in the country - North Shropshire and the local vegetation? And what do Gall wasps actually do in the garden? You've got me intrigued!

I don't think so, they can be either yellowish or red, it's just I've rarely seen them at all, and when I have, they happen to have been red.

Cynipidae is the genus name of gall wasps, and there are loads of different ones, the commonest being Oak Gall Wasp. Figs are largely pollinated by another gall wasp, and many of them function as pollinators, albeit inadvertently. They also provide food for birds - birds may well try to get at the grubs in your pincushion, so they may never mature. Other than that, I don't know much about their life styles, except to say that this particular gall wasp which has laid eggs on your rose is a herbivore.

Thank you bamboo. As I tell my boys you're never too old to learn! Fascinating....