In Iowa, Canadian hemlocks grow best in the eastern portion of the state. When planting rhododendrons, site selection is extremely important. Rhododendrons perform best in protected sites in partial shade. An area that receives morning sun and afternoon shade would be a good site for rhododendrons. Windy and exposed sites should be avoided.
Rhododendrons also require well-drained, acid soils.
An excellent way for home gardeners to lower their soil pH is to incorporate Canadian sphagnum peat into the soil prior to planting. Selecting and planting shade tolerant trees and shrubs, along with suitable annuals and perennials, can transform bare shady areas into attractive landscape sites. Iowa State University , Ames, Iowa. This information subject to a usage policy .