i live in detroit should i prune my gauras now meaning fall or should i wait until spring. This is the first season i planted them midsummer.
Wayne County Michigan
As far as specifically cutting back any perennial, there are individual factors at work.
1. Any foliage that is diseased should be cut back.
2. If you want to provide food for birds, and the plant has seed heads, don't cut back that plant.
3. Grasses have nice winter interest, so don't cut them back until spring.
Personally, I cut back many perennials with seed heads, because it leads to a lot of unwanted self-seeding in my garden.
After looking into specifics for Guara, I found this link that says that Guara dies all the way back, so I would cut the foliage back if it were in my garden. I seem to have more time in fall than I do in spring, so I tend to do more cutting back in fall than some gardeners.
It's been many years since I grew Guara, but I do remember replacing it several times before giving up. When I read in this link that they can be short-lived, I will agree to that! I think that it's because they flower so profusely!
Cutting back perennials in general:
I hope that this helps.