| An Overview of Planting Mixes
One of the first books written on indoor growing suggested that
the entire floor of a grow room be filled with soil. This method
is effective but unfeasible for most cultivators. Still, growers
have a wide choice of growing mediums and techniques; they may
choose between growing in soil or using a hydroponic method.
Most growers prefer to cultivate their plants in containers
filled with soil, commercial mixes, or their own recipe of soil,
fertilizers, and soil conditioners. These mixes vary quite a bit
in their content, nutrient values, texture, pH, and water-holding
capacity.
Potting soil is composed of topsoil, which is a natural outdoor
composite high in nutrients. It is the top layer of soil,
containing large amounts of organic material such as humus and
compost as well as minerals and clays. Topsoil is usually
lightened up so that it does not pack. This is done using sand,
vermiculite, perlite, peat moss, and/or gravel. Potting soil tends
to be heavy, smell earthy, and have a rich dark color. It can
supply most of the nutrients that a plant needs during the first
two months of growth.
Commercial potting mixes are composites manufactured from
ingredients such as bark, wood fiber, composts, or soil
conditioniners such as vermiculite, perlite and peat moss. They
are designed to support growth of house plants by holding adequate
amounts of water and nutrients and often require fertilization
from the outset. Many of them may be considered hydroponic mixes
because the nutrients are supplied by the gardener in a water
solution on a regular basis.
The texture of the potting mix is the most important consideration
for containerized plants. The mixture should drain well and allow
air to enter empty spaces so that the roots can breathe oxygen.
Mixes which are too fine may become soggy or stick together
preventing the roots from obtaining required oxygen. A soggy
condition also promotes the growth of anaerobic bacteria which
release acids that eventually harm the roots.
A moist potting mix with good texture should form a clump when it
is squeezed in a fist; then, with a slight poke, the clod should
break up. If the clod stays together, soil conditioners are
required to loosen it up. Vermiculite, perlite or pea-sized
Styrofoam chips will serve the purpose. Some growers prefer to
make their own mixes. These can be made from soil, soil
conditioners, and fertilizers.
Plants grown in soil do not grow as quickly as those in
hydroponic mixes. However, many growers prefer soil for aesthetic
reasons. Good potting mixes can be made from topsoil fairly
easily.
Usually it is easier to buy topsoil than to use unpasteurized
topsoil which contains weed seeds, insects and disease organisms.
Outdoors, these organisms are kept in check, for the most part, by
the forces of nature. Bringing them indoors, however, is like
bringing them into an incubator, where many of their natural
enemies are not around to take care of them. Soil can be
sterilized using a 5% bleach solution poured through the medium,
or by being steamed for 20 minutes. Probably the easiest way to
sterilize soil is to heat it in a microwave until steam appears -
about 5 minutes per gallon.
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