I have a large Garrya Elliptica, or catkin bush by the back door, growing up against a stone wall, but over the years it had got wider and wider until last year it was some three feet or more wide, necessitating a detour on every trip along the pathway. So I cut it back very hard indeed, so hard in fact that there was no foliage left on it at all, only bare branches. But as you can see from the above picture, it has come back all the more vigorous this year, although I have had to forego most of the catkins for this season as they appear on one year old wood, and so I'm hoping for a good show next year.
This is what the catkins look like, in case you're not familiar with this shrub. Well worth growing for it's toughness, and shiny evergreen foliage. And the catkins come very early in the year, in the middle of winter really, when you really do appreciate them. But it's a vigorous plant and you really do have to keep on top of it if it's not to get out of hand. As soon as the catkins have faded get the hedge trimmer out and run over the whole plant, cutting off all the old catkins and a good proportion of foliage. The plant will then have the rest of the year to prepare for another fine show next winter. If you're buying a new plant the variety "James Roof" is recommended for it's extra long catkins.