rhododendrons and azaleas

by gladys jeurink  

They are beautiful!! They are not natives to Nebraska and in general do not like it here.  They will survive but you’ll have to work a little harder to keep them happy. 

They are shallow rooted and like a damp but not wet soil.  This means in a dry winter you’ll need to water during Christmas vacation and around Valentines Day (if it is warm enough to get outside) as some of the rhododendrons retain their green leaves all winter.  Azaleas usually lose their leaves but still need the water. Quite often I will apply Wilt-pruf around Thanksgiving and then again on a warm day in late January.  Wilt-pruf is a waxy spray that coats the leaves and helps to keep the water from evaporating from the leaves when the soil is frozen, and the plant has a hard time taking up water. 

Our soil is not to their liking either.  Our soil tends to be near or above 7 pH (neutral) so you’ll have to add material before planting in good volume. This can be acid peat moss, pine needles, or other acidic type of compost material, plus granular horticultural sulfur (not sulfur fungicide). As these plants require protection from summer hot sun and winds they are often on the north or east side of the house and close to the foundation which creates another problem. The alkali and lime dissolving off the cement foundation, or a driveway, into your soil, raises the pH. Also the water in Lincoln tests out between 6.5 pH and 7 pH so tends to keep the soil too alkaline for these plants.  They are like blueberries, holly, and evergreen type trees and like a pH of around 5.5. Therefore, granular horticultural sulfur needs to be added at least once a year to counteract this and the tendency of soil to revert to its natural pH.    

Horticulturists have been working with azaleas and rhododendrons for years and have now developed some that do better in our Hardiness Zone 5.  The Northern Lights series of Azaleas do much better than their ancestors.  The PJM rhododendrons blooms a little earlier, have smaller leaves and smaller blooms, but can stand more exposure, and do better here in Hardiness Zone 5. 

To sum up, azaleas and rhododendrons grow best:

          1.          Mulched to cover shallow roots,

          2.          In very acidic soil,

          3.          Protected from the wind and hot sun,           and

          4.          In moist soil. 

For more information send a self addressed stamped envelope (SASE) to Lancaster County Extension Office at 444 Cherrycreek Road, Lincoln, NE 68528-1507 and ask for NebGuide #G97-1341 (Landscapes for Shade), or NebFact NF77-94 (Plant Nutrient and Soil Acidity). 

NebGuides and Educational Circulars (G and EC) and some NebFacts (NF) are also available on the internet. Go to www.ianrhome.unl.edu/search and type in the name of the plant, or the subject, or the name of the pest (insect or disease or weed).

June 5, 2005