Beautiful azaleas are grown in the North Central states despite two handicaps in increasing them. The first is well understood and does not need elaborate discussion: we are primarily in limestone country, and azaleas demand acid soil.
The second and far more severe handicap is mycorrhiza. In azalea country, mycorrhizal fungi are taken for granted.
Still, in the Midwest, the gardener needs to be told that all acid-soil plants, including broad-leaved evergreens, blueberries, and azaleas, depend upon these highly specialized soil fungi surrounding the roots and even grow into the root pores for their growth.
Without mycorrhiza, acid-soil plants survive feebly but don’t thrive. The fungi live in soils high in organic matter but cannot reproduce themselves unless growing on a plant root. Therefore, acid-soil plant culture in the Midwest has become a culture of mycorrhiza to a considerable degree.
Growing Azalea In Midwest
To grow azaleas in the Midwest, we need a soil high in organic matter containing mycorrhiza and acid. Imported peat moss is a good source of organic matter because it is acid. Domestic peat should be avoided for azaleas because it is often alkaline.
Many gardeners depend upon oak leaf mold because they think this will solve their problem but are amazed when their plants die. True, the leachate or run-off from decaying oak leaves is strongly acid, but a neutral mold remains after the leaf mold is thoroughly leached.
Always check pH (the degree of soil acidity) with a simple kit available for a dollar or two. If the soil is still not acid after mixing in peat moss, chemical treatment will be necessary to reduce the pH. The buffering action of our fine prairie soils is tremendous even after adding as much as 25% percent of the total volume of the soil in peat.
Preparation of the soil should be to a depth of 24″ inches. Be sure the planting bed is underlaid with coarse gravel or good drainage material. This prevents the too rapid rise of soil water from below the treated area. Such water will be alkaline and leaves enough lime to cause trouble.
Earthworms in Azalea
Earthworms are also troublesome in maintaining acid soil in the Midwest because their castings arc is usually alkaline, and they, too, gradually change the reaction of the soil. Treating the soil with chlordane will eliminate them and several other soil-borne pests.
Our domestic water supplies are almost always alkaline. While this is not as serious as many persons feel, since the amount of suspended mineral matter in 100 gallons of water may be less than a teaspoonful and can be neutralized quickly, it can result in a very high or alkaline pH reading.
To balance the mineral matter, add acidifying chemicals to the water through an inexpensive siphon device attached to the hose when you water.
There is sufficient moisture in the soil in spring, but from mid-June on, we must apply water liberally and preferably through one of the fine mist nozzles that create a fog around the plant. Azaleas are high-humidity plants.
Fertilizers In Azalea
Fertilization is another important consideration in the Midwest if you want beautiful azaleas. Foliar feeding regularly in light applications seems beneficial, but the most important fertilizer application of the year is made to the soil in mid-August.
Applying a highly soluble form of nitrogen, such as ammonium sulfate or ammonium nitrate, is recommended. This feeding aims to ensure the plant’s ability to manufacture and store food on which to begin early spring growth before the mycorrhiza is active in the soil.
Incidentally, all acid-soil plants, for reasons one doesn’t know, like their nitrogen in the form of ammonium rather than as nitrates.
Because of the intensity of sunlight in the Midwest, we must provide light, filtered shade for all azaleas in winter and summer. In my experience, azaleas grow best on the north side of an evergreen hedge or a building but far enough in front of it so spring and summer sun reaches them.
Variety Selection
We naturally get them on their roots since we depend on species rather than hybrids or named varieties. However, when the venturesome gardener does try hybrids or named varieties, he should avoid grafted plants as they are not as hardy as own-root plants.
The list of azaleas we can grow is definitely limited. Three of the best are Azalea obtusa Kaempferi, Azalea pottkhattensis and Azalea Schlippenbachi. These are subject to bud loss if exposed to temperatures below zero, but this can be overcome by caging the plants with chicken wire and filling the cage with evergreen boughs, excelsior, dried oak leaves or any other light, airy mulching material.
Azalea mollis and its hybrids are all hardy with us if protected from drying winter winds and sun. The native Azalea canadensis, Azalea calendulaceum, Azalea arborescens and Azalea Vaseyi seem to survive if kept moist and are grown in an open oak woods.
44713 by R. Milton Carelton