Thanks for your question Jen. It’s great that your rhododenrons are doing well on their own. That tells us that they are planted in a location that suits them and that’s half the battle right there. You should prune them right after they flower in spring. Rhododendron, azaleas and other broadleaf evergreens form their flowers buds during the summer and fall. Those buds must winter over and then open in spring. If you prune them late in the season, you’ll be removing the flowers you wish to enjoy. As always follow the pruning rules of 1/3. Never prune off more than 1/3 of the branch structure. Usually that isn’t necessary but if it is, prune it partway back then wait a year to do more. It is also a good idea to snip off the remnants of the flowers in spring. If you remove the seed pods then the energy the rhodos would have put into those seeds will go instead into more flowers the following spring. I like cedar mulch but and good bark mulch will be fine. You can mulch 4″ deep but make sure that you don’t pile mulch up against the trunk. That can smother the bark and cause more harm than good. I really like Espoma Holly-tone. It is a granular food that you should apply as early in the spring as you can. I like to pound hole with a small length of pipe down about 8″ and then pour the Holly-tone down the holes. That gets the food to the roots that can absorb it. You’ll need several holes and they should be made out away from the trunk of the Rhodo about as far as the outermost branch tips. Scattering the food on the mulch is wasteful since the nutrients have a hard time making it through the mulch into the soil where the roots are.