One of the difficulties in growing azaleas in many areas west of the Appalachians, in western Pennsylvania and Ohio, for example, is that the soil is not naturally acid and is often alkaline.
In addition to this, much of the water supply is hard so it quickly counteracts any artificial acidification of the soil.
This should not prevent you from enjoying azaleas, however. For those areas where the soil is not naturally acid, the best results are usually obtained by planting the azaleas in pure acid peat moss.
This should be at least a few inches beneath the roots and 6” inches or more on each side of the root ball.
Artificial Soil Acidification
When azaleas are planted where the soil is not naturally acid, and the water is hard, it is better to let them suffer from drought than water them with hard water.
Even if you plant your azaleas in acid peat moss, artificial acidification is advisable at least once a year, and 2 or 3 applications may be advisable if hard water is applied.
Using iron sulfate, also called copperas, is inexpensive and usually easy to obtain.
For neutral or slightly alkaline soils, apply 6 ounces of iron sulfate per square yard.
For soils slightly acid but which need to be made even more acid, apply 3 ounces per square yard.
Apply the lighter amount and wait 2 weeks to see if the foliage becomes dark green.
If not, repeat the application. Just scatter the iron sulfate on the soil’s surface and let the rain wash it in.
Proper Light Requirements
Azaleas may be grown in sun or shade, and if the hardy forms are used, the wind should not be a limiting factor.
For varieties of doubtful hardiness or those growing in an east or north exposure, reducing the amount of winter sun with natural or artificial shading may prove beneficial.
Different Azalea Varieties
For very early bloom, about the same time as mid-season daffodils, try Azalea mucronulata. Its flowers are a pale rose-purple.
Do not plant it in a frost pocket, as late frosts may damage the bloom.
The Chinese Azalea or Azalea mollis and its hybrids are as hardy as the above and are early blooming.
Completely hardy, with purple-lilac flowers, is Azalea poukhanensis. Closely related to it is Azalea yodogawa, which has double purple flowers.
These species grow relatively low and compact, suggesting their use as color accents in your foundation planting.
Not as hardy as the above varieties but worthy of trying because of their wide color range are the Azalea Kaempferi hybrids, ranging from pink to red through salmon shades.
Some of the more common varieties include:
- Cleopatra
- Louise
- Carmen
- Theodora
These hybrids tend to be semi-evergreen, are relatively low growing, and make excellent subjects for shrub borders or foundations.
The brilliant Ghent hybrids, hardy here, are easy to grow. However, while not so easy, the native flame azalea or Azalea calendulacea is well worth trying, for its magnificent yellow-to-burnt-orange flowers will highlight any garden.