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HORTICULTURAL VERMICULITE
(Photo
courtesy of The Vermiculite
Association)
Vermiculite is the geological name given to a group of aluminum-iron magnesium silicates
with the appearance of mica. When processed for horticultural use, the
mineral is introduced to intense heat, expanding the granules into multiple
layers of very thin plates to create an accordion-shaped planting medium.
Vermiculite has been used for many years to amend potting soils and outdoor
mixes, in turfgrass and outdoor plantings, for 100% vermiculite growing
applications, and for hydroponic growing and water conservation. Horticultural vermiculite improves soil aeration while
retaining the moisture and nutrients necessary to feed roots and rhizomes
for superior growth.
Consider the
following reasons for using horticultural vermiculite in your Deep South
iris garden:
1.
Horticultural
vermiculite is permanent, clean, odorless, non-toxic and sterile. It does
not deteriorate, turn moldy or rot. The pH of vermiculite is neutral to slightly
alkaline (7.0-9.5), which is a perfect growing culture for bearded irises.
2.
Vermiculite
possesses cation exchange properties, so it holds ammonium, potassium,
calcium and magnesium and makes these available to the roots and rhizome.
3.
When mixed
with composted or natural soils or mediums, vermiculite promotes faster
root growth, and gives quick anchorage to newly planted rhizomes. These
mixes help retain air, nutrients, and moisture to release them as needed by
the plant.
SOIL
AMENDING OR CONDITIONING - Coarse grade vermiculite is the
standard for outdoor horticultural uses, though medium grade may also be used. These grades of vermiculite may be used
directly as poured from the bag. Where the native soil is heavy or sticky
(like our gumbo clay!), vermiculite may be mixed in proportions up to
one-half the volume of the soil. This creates air channels and allows the
soil mix to breathe. Mixing vermiculite in gardens will provide the
necessary air to maintain vigorous plant growth. When soils are sandy, the
use of vermiculite will help the soil hold the water and air needed for
growth.
If the garden area is very large, you may choose to condition only
the rows where planting is to take place. If this procedure is continued
for two to three years, the entire garden area will eventually be
conditioned. Because horticultural vermiculite is inorganic, it will not
deteriorate in the soil but will continue to function for many years.
When vermiculite is used in the potting application of
new rhizomes (with soil, peat, composted pine bark, or other properly
composted soil materials), no additional feeding may be required right up
to the time of transplanting. Because vermiculite is sterile, the threat of
"damping-off" is virtually eliminated. Later, the young iris
plants can be removed from vermiculite with little danger of breaking off
hair roots, and the dense root growth enables young plants to take hold in
the garden immediately. Using vermiculite during the potting procedure also
lightens the mix, making the transplant process even easier!
SUMMER MULCH - In summer's hottest months, use vermiculite to
mulch around the rhizomes (or even your other shrubs, vegetables and garden
plants). The vermiculite will help prevent drying out, as well as insulate
your plants against the extreme heat. Vermiculite does not mat down or
become soggy because its pore structure prevents it from becoming
saturated. If applied around plants after the first heavy summer rain,
vermiculite will help prevent drying of soil and damage to your plants.
Vermiculite acts as a constant reservoir of moisture, thus retarding drying
out and scorching during dry spells.
FLORAL ARRANGEMENTS - After
your babies begin blooming, you will want to bring some of those lovely
blooms inside to enjoy. Fill your container with vermiculite and level off.
Thoroughly saturate the vermiculite with the tap and then pour off the
excess water. Arrange your flowers as you would normally for a beautiful
arrangement. Flowers arranged in vermiculite will remain fresh for days
with no concerns about water spillage. With taller containers all you need
to use is the moistened vermiculite. With centerpieces or top-heavy
arrangements, chicken wire may be used to hold the flowers erect.
STORING
RHIZOMES - Vermiculite can also be used at digging time. After you have
provided a bleach bath for your newly dug rhizomes, allow them to air dry
in the sun. After the rhizomes are fully dry, place them in a storage
container and pour vermiculite around them. The absorptive power of
vermiculite acts as a regulator that prevents mildew and moisture
fluctuation during the storage period. It will not absorb moisture from the
inside of the rhizomes, but it does take up free water from the outside,
preventing storage rot. Stored rhizomes are also protected from temperature
changes.
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