Pruning sweet cherry trees
In general, sweet cherry trees should be pruned when the tree is dormant--i.e., when it does not have leaves. There are a couple of reasons, but probably the best is that with the leaves off it is easiest to see just how the tree should be pruned in order to maximize fruit yield, tree health, and worker safety. That said, additional pruning can be done a other times of year, and in fact espaliered trees will need to be pruned several several additional times during the summer.
Do you have five trees? Or one tree with five varieties? Are they are on dwarfing rootstock --and if so, do you know what variety of rootstock? How long ago did you plant your cherry tree(s)? How large are they? Are they bearing well now? Most important, what do they look like now? What are your reasons for pruning--are the trees too tall? Overgrown and disorderly? Brand new (tiny) and in need of a good start? All pruning cuts are a wound to the tree, and appropriate pruning is never more than absolutely necessary--which severely limits how useful advice can be in forums like this!
Instead, we recommend that you take multiple photographs of your tree (cell phone photos are great.), and email them to your local Master Gardener office with a clear statement of what you are trying to accomplish with the pruning, and they will be in a much better position to give you specific advice. Note that it is likely that they will want to call you for additional information, so include your phone number (and good times to reach you) when you send your photos by email.
The email address for the Washington County Master Gardener office is firstname.lastname@example.org. Their phone is 503 821-1150 x 2.
That said, here are several excellent resources that should also prove useful:
Brickell and Joyce, The American Horticultural Society Pruning and Training. This book is readily available from your library (and no, that title is NOT a typo).
The Home Orchard Society, with a fruit tree arboretum on the Clackamas Community College campus, provides excellent hands-on training opportunities several times a year. More info at: http://www.homeorchardsociety.org/.
OSU Extension Publications--generally free online:
Growing Tree Fruits and Nuts in the Home Orchard: https://catalog.extension.oregonstate.edu/ec819.
Cherry Training Systems: https://catalog.extension.oregonstate.edu/pnw667.
Training and Pruning Your Home Orchard: https://catalog.extension.oregonstate.edu/pnw400