Unfortunately,
not everyone (actually hardly anyone) has the ideal soil
for growing ornamental plants in the landscape. Such a
soil would be light and airy with great drainage and
enough organic matter to support a thriving population
of soil organisms. It would hold water and nutrients in
the root zone of the plants and would not change much
regardless of the foot traffic that travels over it.
Well, there certainly are
naturally occurring soils that meet these criteria. They
generally have the term "loam or loamy" attached to
them. But, for many of us, our landscape soils will
present certain "challenges" that we must attempt to
address if we are to have success with our plants. These
would include:
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Heavy or Clay Soils - Clay particles are
extremely small and generally flat in nature. They
pile on top of each other resulting in an extremely
tight fit. This leaves no space for air or for water
to move so these soils are characterized as being
poorly drained and subject to compaction. They often
form a hard surface that does not allow seedlings to
emerge or for water to penetrate. These are tough
soils in which to grow plants!
What to do about it -
Adding large amounts of organic matter (OM) such as
compost, peat moss or other such products will
improve clay soils. The OM will help to form larger
clumps which will have bigger pores for air and
water. This helps with root growth and improves
drainage to make the soils more plant friendly.
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Light or Sandy Soils
- Just the opposite of clay, sandy soils are made up
of relatively large particles. This results in very
large pore spaces which result in water moving
through rapidly. That is why these soils tend to be
"droughty" and require more frequent watering. Also,
sand has a poor electrical charge and does not hold
onto nutrients like
clay. This allows the nutrients
to also flush through the soil quickly along with
the water.
What to do about it -
Adding large amounts of organic matter (OM) such as
compost, peat moss or other such products will
improve sandy soils. The OM will "clog" the large
pores and absorb water as it moves through making it
available to plant roots. Also, OM has a great
ability to hold onto vital plant nutrients so they
are not so easily leached through the soil.
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Soil
Compaction - This occurs when the 50%
pore space of an ideal soil is squeezed together and
lost. Without adequate poor space, there is not
enough oxygen or water for proper root growth. It is
a primary problem of
clay soils which already have
limited pore space and the small particles are
inclined to compact together. Vehicle traffic such
as construction tools, lawn mowers and even foot
traffic all contribute to compaction.
What to do about it -
Adding large amounts of organic matter (OM) such as
compost, peat moss or other such products will
improve clay soils and thus minimize compaction. The
OM will help to form larger clumps which will have
bigger pores for air and water. This helps with root
growth and improves drainage to make the soils more
plant friendly.
Tilling the soil can also help eliminate compaction.
That is why it is a good idea to double dig new beds
and borders to loosen the soil. In lawns, core
aeration will help minimize the problem. Removing
cores of soil to a depth of about 2 inches or more
will allow air and water to penetrate into the root
zone of the turfgrass.
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Subsoil as Topsoil - Unfortunately,
during the construction of houses, the contractor is
required to dig a basement that is 7 to 8 feet deep.
This requires excavating many cubic yards of subsoil
which needs to be removed. All to often, this soil
is merely spread out over the lot on top of the
existing topsoil. What's even worse is that it may
then be pounded down under the weight of earth
moving equipment or trucks.
Plants are meant to live primarily in a layer called
the topsoil. This is usually the top 6 to 18 inches
of soil that contains organic matter and has a
structure capable of supporting plant life. Beneath
this layer is a type of soil called subsoil. It does
not have the organic matter or physical structure
needed for plant life. It will often be a fine
textured soil that will become very hard once it is
spread out onto the surface.
What to do about it -
Adding large amounts of organic matter (OM) such as
compost, peat moss or other such products will
improve subsoils and thus minimize compaction. The
OM will help to form larger clumps which will have
bigger pores for air and water. This helps with root
growth and improves drainage to make the soils more
plant friendly.
In some cases, you may need to either replace the
layer of subsoil or add significant amounts of good,
loam topsoil. Remember, that to grow good turfgrass
you will need at least a 6 inch layer of the
topsoil. Adding a few inches will not do the job.
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Shallow
Soil - In some areas, there may be only a
few inches of actual topsoil on top of a rock
hardpan layer. This is generally not enough to grow
most ornamental landscape plants. Some of them may
survive on this limited topsoil layer but few will
thrive over the long run.
What to do about it -
You may need to add significant amounts of good,
loam topsoil to improve this type of situation.
Remember, that to grow good turfgrass you will need
at least a 6 inch layer of the topsoil. Adding a few
inches will not do the job.
In the extreme, you will need to choose your plants
carefully. This is especially true with trees and
shrubs that need to develop extensive root systems.
There may be species that can survive better under
thin topsoil conditions. Often plants that are
native to the area have shown that they are adapted
to it.
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