Specifically, Richard Chaikin of ARS recommends “40 percent coarse perlite, 40 percent conifer bark ... can damage the roots. Since overuse of plant food may burn sensitive roots, rhododendron ...

The Rhododendron is a small tree or shrub growing up to about 3m. It has a characteristic gnarled and dwarfed appearance. The bark is dark grey, thick and furrowed. The branches are stout and twisted.