I love Azaleas and Rhododendrons and they grow well in my garden on the acid soil.
Here is a study of Rhododendron ponticum. It has lovely orange marks on the upper petals.
The ferns are irresistible to sketch at the moment, unfurling in every hedgerow. I'm hoping to do a fern painting when I get time. These harts tongue ferns have shiny highlights and lots of scales and hairs to convey.
I bought 2 new paintbrushes from Rosemary and co. (www.rosemaryandco.com/) , on a recommendation from a friend. They are superb and now my favourites. I highly recommend them too.