Well you can do it, but you may sacrifice flowers and those bright orange berries you get in mid-summer. I would wait until it flowers in a few weeks, then give it a trim. Then you'd be able to work around the blossoms.

I imagine its already flowered and berries are forming, so yes you can trim back, but if you can bear to wait until the beginning,middle or, even better, the end July, you will get less regrowth than you will if you do it now. Once we get past the longest day on 21st, plants start to respond by slowing down their rate of growth....

Interesting question! I planted a full hedge of this at the front, but it need to be kept short so that we can see up the road to exit the drive. The hedge is probably 50-60 ft total and it gets cut twice a year by hand, each piece by secateurs to prevent either cutting off buds or after flowering, berries. Great fun, but it probably amuses the neighbours! But Wow it looks stunning when in full bloom or full berry, worth all those hours of cutting.

Great fun? I replaced mine with hydrangea because I hated getting stuck. Those spikes can pierce thick leather gardening gloves.

Thank you all for your comments. Honeysuckle, I agree, put in the hard work and it pays dividends- I love my pyracanthas (plural) :)