What is this? (It is not a hydrangea!)

[Namechange4065]

Every year this plant appears with long thick stems and I usually cut it back becasue I thought it might be a runner off a nearby tree. This year it's flowered (I haven't cut it back) to my surprise. It is right next to/sort of coming through an existing viburnam I have and seems to come from the same root.

It really isn't a hydrangea I promise - the flower is quite different - but the only other identification I can make is a Viburnum lantana or Wayfaring Tree. This is not the viburnum I have and why is it flowering now (viburnums are usually early spring?). Are viburnums ever grafted onto other stock plants?

Any thought most welcome.

There are umpteen different varieties of viburnum, and that is indeed one of them. The flowers smell horrid and the stems are hairy, if memory serves me right.

Possibly viburnum rhytidophyllum maybe. They are very vigorous, so perhaps your one was grafted on to a rootstock, and it is that which is now growing and taking over.