Rhododendrons and Other Ericaceae
From Nursery Notes, Cornell University
1959 census figures showed a tremendous increase in sales of broadleaved evergreens in New York State as compared to earlier years. One likely reason for this increase is that homeowners are realizing that with proper attention, these plants can be grown satisfactorily.
Three important considerations in growing rhododendrons and other ericaceous plants are (1) careful selection of site, (2) ensuring well-aerated and well-drained soil and (3) plant maintenance after planting. Customer education by nurserymen on these three points gives better customer satisfaction and a desire to purchase more of the same plants.
Requirements for best growth of shallow-rooted ericaceous plants are: winter temperatures above the minimum for each cultivar; porous, well drained soil with high moisture-holding capacity, high organic matter content, and acid reaction (low pH); protection from excessive wind and full sun, protection from pests; use of a mulch. Rhododendrons planted in poorly drained and aerated soils can be placed in prepared raised beds containing peat moss, or a mixture of 50 percent peat, 25 percent sand, and 25 percent soil. The beds should be 6 feet wide by at least 12 inches high; the edges of raised beds can be held in place by either a low retaining wall or ground covers. In well-drained loamy soils, prepare ground beds and back-fill with a 50 percent peat-50 percent soil mixture. For more detailed information see Cornell Extension Bulletins 1071 and 1091 on the culture and problems of rhododendrons in New York.