Rhododendrons in Missouri
Carl L. Penzel, Jackson, Missouri
I feel that I have not done much for our Society, but I am enclosing some notes that may be of interest. I seem to detect, sometimes, by inference from some of the contributors to our Bulletins that our part of the country is a barren no mans land in the rhododendron world. I must admit that the native azalea rosea can not be dug with a shovel but a pick must be used because of the gravel in the soil. I have been told the azalea rosea shown in the parks are over 50 years old and have withstood land clearing, constant cattle grazing, a few years of goat grazing and a few fires along with children selling the flowers for 10 cents per bouquet. These azaleas bloom about May 15-20 and are native to the Ozark region in the south one-fourth of Missouri.
The Rhododendron roseum in the parks along with the older plants have received no care while the younger plants have been fertilized and watered. The owners picked a bouquet for us before we could stop them!
I am keeping notes of winter damage to azaleas and rhododendron at my home. H2 rhododendron will withstand our climate without damage in sun or shade to -10. H3 types need shade to prevent leaf burn but otherwise do not suffer too much; H4 types lost all of their leaves this winter and last winter and they had no protection except being under high oak trees. Burlap screens may help, but otherwise H4 are unsatisfactory.
I use a mixture of pulverized cow manure, cotton seed meal and commercial azalea fertilizer mixed in equal parts once a year. Mulch with two-inch oak sawdust topped with one half inch of cotton seed hulls to keep the water from running off of glazed surface of the sawdust. I use iron chelates and also Epsom salts, one teaspoon per gallon of water as separate drenches about three times a year with each. I use fish emulsion fertilizer sparingly before July 1 only if a plant needs a boost.