soil which is acid or which can be acidified. In soils which are not 
quite acid enough, ammonium sulphate, properly used, will increase 
the acidity of the soil and also provide a good source of nitrogen. On 
soils which are near the neutral point it would probably be desirable 
to acidify with sulphur. 
Rhododendrons normally require a considerable amount of or- 
ganic matter in the soil. This may be added in the form of peat moss, 
leaf mold, sawdust or well-rotted manure. Where sawdust is 
used, or for that matter where any other dry organic matter which 
has only started to decay is applied, it will be necessary to add addi- 
tional nitrogen. Usually at least twice as much nitrogen will be 
needed for soil which has had sawdust worked into it, or applied as a 
mulch, as would be needed if the sawdust were not used. When 
planting in heavy soil mix peat moss or leaf mold with the soil to be 
filled in around the plant. Set the plants about an inch deeper than 
they grew at the nursery. More and more, Rhododendron growers 
are using a mulch of peat moss, sawdust, leaves, or other organic 
matter. This keeps the soil cooler in Summer, conserves moisture, 
and of course adds organic matter as it decays, besides providing 
some protection against Winter injury of the base of the trunk and 
the roots. To be satisfactory a mulch should be deep enough to 
prevent the growth of most weeds. In very dry periods it will be 
advisable to check the moisture under the mulch and perhaps apply 
additional water. Rhododendrons are rather sensitive to dry weather 
and ample watering is advisable. 
Rhododendrons are often said to be shade plants but they do not 
like heavy Shade, especially under trees where there is competition 
with the trees for water and plant food. The north side of a build- 
ing where the Rhododendrons may get a little direct sun in morning 
and evening, is a very desirable location. Certain small trees pro- 
viding light shade may be the best where there is ample moisture 
and plant food. Where the soil is very dry and where competition 
with trees would be a serious factor, it may be practical to build a 
lath shade. In warm climates, lath houses provide a pleasant place 
for the gardener to work and to enjoy the Rhododendrons as well as 
giving them the conditions they require. Lath houses may be con- 
structed fairly cheaply and if well designed and well located, they 
can be an asset to the garden. 
Rhododendrons require about as much fertility as other garden 
plants. The fertilizer, of course, should not contain lime, as lime 
is definitely undesirable for Rhododendrons except under extremely 
acid conditions. 
Azaleas, as a group, are somewhat more tolerant of direct sun- 
shine, higher Summer temperatures, and drier conditions than are 
Rhododendrons, 
