I'm new to Riverton, UT (SLC suburbs). There is a huge rose bush in front of our rental house that needs a pruning really bad. When is it safe to do so? I've heard don't plant until Mother's Day. Should I wait that long?
Planting is different than pruning. Since the rose bush is already out there, it has dealt with the cold.
At least a few weeks ago, a maybe even a month, Larry Sagers, the USU Horticulture Specialist at Thanksgiving Point, told listeners on his Saturday morning KSL radio show to, at the very earliest, wait until the end of his show that morning to prune rose bushes.
I won't go into technique, but if you are already seeing new growth on your rose bush, then you will want to hurry and prune so that the new growth efforts can be focused on what you don't prune off.
I am including a link to an old article on KSL about roses in Utah and briefly on pruning them.
Here is a link that might be useful: Gardening Success Begins With Roses