Improving Grow Mediums with Diatomaceous Earth

Posted on May 30, 2021 at 7:30 PM

Improving Grow Mediums with Diatomaceous Earth

Depending on mining and processing, diatomaceous earth may be sold as chunks of stone or ground into a powder. Since the frustules (broken or whole) still have voids and holes, they are much lighter and more porous than a solid piece of silica would be.


Diatomaceous earth is used in a variety of ways. It is used as a mild abrasive in polishes, toothpaste, and facial scrubs. It is used as a liquid absorbent, in some flea powders, and can be used as cat litter. It is an important component of dynamite (diatomite soaked with nitroglycerin). It can be heat treated and used as a filtering material for drinking water, swimming pools, fish tanks, beer, wine, and other liquids. It is also used as an anti-caking agent in grain storage. In gardens DE is used as both as a growing medium additive and as an insecticide.


Diatomaceous earth for gardening should be amorphous silica and not heat treated or contain much in the way of crystalline silica or active contaminants. Chunks of DE may be used as a component in a growing medium. By virtue of the voids within the material, it holds both water and air well. It can be added to a potting mix or an existing soil as an improvement or used by itself as a hydroponic medium. Diatomaceous earth is high in soluble silica, and while silica is not generally considered a plant nutrient, many plants (especially monocots) can make use of it to reinforce their cell walls, which can strengthen and fortify them against insect damage.


(Read also: What Grow Medium Is Right For You?)


Dry-powdered DE is used as a mechanical insecticide. It absorbs fats and oils from an insect’s exoskeleton while the sharp edges cut and damage. With the reduction of the protective fats and oils on the exterior of the insect, the fluids inside more easily evaporate, dehydrating and killing the insect.


It can be applied by either sprinkling dry or mixing with water to apply and then allowed to dry. While DE is not poisonous, breathing any dust can have detrimental health effects so precautions should be taken to avoid excess inhalation. It is frequently applied to the medium around the plant but may also be used on plants themselves. If used directly on plants, avoid harvestable portions as it can leave a (mostly harmless) residue, and avoid spraying flowers to protect bees.


Diatomaceous earth can be used in a variety of ways, and with care and judicious use can be a valuable tool to add to a gardener’s bag of tricks.



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