Michigan State University, Cooperative Extension Service, by Clarence E. Lewis, Professor, Horticulture and Douglas J. Chapman, Extension Horticultural Agent, January 1971. Flower buds are prominent, terminally borne, and enclosed in prominent bud scales. Rhododendron catawbiense Catawba Rhododendron 1. Round shrub, 6-lO' high, dense.
Buds conical with rounded base, without leafy scales.
Rhododendron maximum Rosebay Rhododendron 1. Round mound, somewhat tree like 6-20' high, tending to become straggly and open. Buds conical with leafy, outside bud scales. Rhododendron smirnowii Smirnowi Rhododendron 1. Round mound 6' high, dense and very slow grower.