We didn’t do it earlier in the year and my garden helper really wants to do it now. But I am worried that it might be too late.
If you do it right away, you should be fine. It’s best to finish pruning about 6 weeks before freeze up and her in Toronto, our first hard frost is around the end of October.
However, there’s always a chance it might be earlier, and there is no harm in leaving the pruning until the spring.
Here is a link to a Toronto Master Gardener Guide on Evergreens Suitable for Hedging, including information about pruning:
and here is a link to Mark Cullen’s Gardenblog entry on pruning cedar hedges: