A major factor in
determining how well your plants or seeds will grow is
their compatibility with your soil. Each plant species
has a range of soil types in which it will flourish. It
is very important to choose your seeds and transplants to
match your soil type.
Soils can be divided
into three basic classifications: sands, loams, and
clays. There is great variation within these basic
groups, but these categories will suffice for the purpose
of describing where a given plant will or will not grow.
referred to as "light" soils, contain large
sized soil particles that are loose and easy to work.
They allow water to drain readily and tend to be low in
nutrients. Sandy soils tend to be more acid than the more
fertile loams and clays. If your soil has a pH lower than
5, consider adding lime or wood ashes to bring it closer
to a pH of 6 or 7.
commonly known as "heavy" soils. Consisting of
very small, tightly packed soil particles, clays tend to
be dense and hard to work. However, they are generally
rich in nutrients, have a high water-holding capacity,
and can be very productive.
"intermediate" between sands and clays.
Composed of many different sized soil particles, they
combine fertility and moisture-holding capacity with good
drainage. Easier to work than clays and better
consolidated than sands, loamy soils make an excellent
medium for growing most plants. Many prairie plants do
best in loam soils.
Your Soil Type
Test" can help you determine your soil type. Take
just enough moist soil to rub between the thumb and
fingers. Rub it back and forth several times and feel it
very carefully. A clay soil will be slick and smooth,
with little or no grittiness. A predominantly sandy soil
will be gritty and will not stick together well. A loamy
soil will stick together easily, but not tenaciously like
a clay. Loams will feel moderately gritty. As the soil
dries between your fingers, rub it into a dust and feel
it carefully. A loamy soil will have a component to it
that feels like flour. This is silt, a soil particle size
between sand and clay. Clays may also have a floury
feeling to them, indicating silt content, but clay soil
lacks the gritty sand component found in loams.
If you have difficulty
determining your soil type by this method, dig into your
soil when it is dry. A sandy soil will seldom exhibit
clods. Any clods that do form will crumble easily. A
loamy soil will have clods that can be sliced cleanly
with a shovel. Clay soils tend to form hard, persistent
clods. Rather than slicing through them, a shovel will
get stuck or will shatter the clod into many hard, little
blocks of soil.
If you are still in
doubt, take a soil sample to your local soils lab for
If you have a sand or
clay soil and wish to improve it, there is no better
method than to add large quantities of organic matter.
Compost and dead leaves are excellent. Do not use
sawdust, wood chips, or similar materials. These require
a long time to break down and rob the soil of nitrogen.
Avoid uncomposted manure. It contains large numbers of
weed seeds. Organic matter holds more water and nutrients
than any other soil constituent. It breaks up heavy
soils, improving water intake and air exchange to plant
roots. Organic matter firms light soils, making them
richer and less drought prone. In each case, adding
organic matter modifies a soil so that it behaves more
like a loam. The benefits of adding organic matter
include increased seedling survival, better root
development, and faster plant growth.
Another effective method
of improving poor soils is to plant a "green manure
crop," such as buckwheat or winter wheat. These
crops improve the soil by bringing up nutrients from the
lower soil and converting them into plant organic matter.
The crop is plowed under while actively growing to
incorporate the roots and leaves into the soil. This is a
cheap, ecologically sound way to build soil organic
Working with Clay Soils
Clay soils with low
levels of organic matter can be difficult to work. The
fine soil particles pack together tightly, impeding
drainage and air exchange. In the heat of summer, clay
soils harden and prevent downward root growth. Clay soils
warm up slower in spring and compact if worked when wet.
Each of these problems will retard root development and
Adding organic matter
helps to "open up" clay soils by improving
porosity or "breathability." This increases
water infiltration and air movement through the soil,
which is critical for good root growth.
There are many prairie
plants that can grow in clay soils, such as our "Clay-Busters". With good initial care,
these wildflowers and grasses will flourish even on
difficult sites. Their roots will gradually work their
way down into the clay, opening and improving it, just as
these plants have done for thousands of years.
Planting in Clay Soils, We Recommend:
Mulching with weed free
straw (clean winter wheat, oat, or marsh hay) to hold in
moisture and prevent drying. Mulch 2 - 3 inches deep for
transplants with openings for the emerging leaves. For
seeded areas, 1 - 2 inches of mulch will help to maintain
upper soil moisture.
Regular light watering
of prairie seedlings for the first two months will
greatly increase germination and seedling survival. Water
when the surface begins to dry out. Mulched areas require
less frequent watering. Water only in the morning to help
prevent disease problems. Do not over-water. Clay soils
hold moisture well and drain down slowly.
Soil moisture is equally
important in deciding which species to plant. Moist soils
have a generous amount of water in the subsoil throughout
the growing season. They may have periods of standing
water in the spring or fall.
Dry soils include sandy
and gravelly soils that drain readily and never have
standing water, even after a heavy rain.
Medium, or mesic, soils
include well-drained loams and clays. These soils may
have standing water for short periods after a hard rain.