We
talk about acidity and alkalinity of the soil but often
don't have a good handle on exactly what that means. Of
course, these terms do not just apply to our soil. They
are used to describe any chemical compound.
Technically, pH is a
measurement of the concentration of hydrogen ions
present. It is ranked on a 14 point scale with 7.0 being
neutral i.e. neither acid nor alkaline. If the pH number
is lower than 7.0 it is said to be acidic while a number
higher than 7.0 is said to be alkaline or base.
The pH scale is what is
called logarithmic meaning that each change of 1 unit of
pH means a 10 times change. So, a pH of 6.0 is ten times
more acid than one of 7.0. A pH of 5 is 100 times as
acidic as one of 7.0.
Most landscape plants do
best with a pH in the slightly acid range between 6.0
and 7.0. A handful of "acid loving" plants such as
rhododendron, azaleas,
boxwood,
blueberries and
pin oak
need a more acid environment between 4.5 and 5.5. A
handful of species, especially those from the Western
part of the
United States
do best in an alkaline soil.
