Here in Northern Ohio, zone 5, Rhododendrons and Azaleas are in full bloom curing late May and early June. Rhododendrons and Azaleas start making new flower buds for next year soon after they finish blooming so the ideal time to trim them is right after they finish blooming. This way you cut off the seed pods from this years flowers and also get the plant trimmed before it has a chance to set any new flower buds. After it is trimmed the plant will set new flower buds and your plants will be loaded up with blooms for next year.
Most people are afraid to trim Rhododendrons because they aren’t sure how to go about it. I just take my hedge shears and cut away, just like I would any other plant. The result is a beautiful plant that is tight and full, and loaded with blooms each year.
Most Rhododendrons and Azaleas are slow growing evergreens so they don’t need or like much fertilizer in fact I never fertilize mine. If you want to make them really happy, just make sure they are planted in good soil that drains well.
If you have a Rhododendron that is doing poorly, chances are it’s in an area that stays too wet. Maybe back by a wall where a downspout drains and the soil stays moist all the time. They hate that so raise it up and put good topsoil around it. You’ll see a difference in the plant.
Mike McGroarty is the owner of McGroarty Enterprises and the author of 2 books. You can visit his website at Freeplants.com.