The naturally occurring, soft sedimentary rock known as diatomaceous earth (DE) is mined from the ancient remains of lakes and rivers all over the world.
The fine powder consists of the fossilized remains of prehistoric algae and phytoplankton – known as diatoms – that lived and died in various bodies of water.
The diatom exoskeleton was made up of silica, and as these single celled organisms piled up over the course of millions of years, they compressed and formed deposits of the porous, sand-like particles we know as diatomaceous earth or diatomite.
Diatomite deposits have been discovered across the globe – from Scotland, the Czech Republic, the Sahara Desert, Germany, Denmark, and the western United States – and each deposit possesses properties unique to its region. This is why DE is sometimes white, or grey, or brown.
In general though, diatomaceous earth is composed of 80-90% silica, an abundant element found in everything from the earth’s crust, to rocks and sand, and within the cells of plants and animals. It also contains varying amounts of calcium, iron, sodium, and several other trace minerals.
Diatomaceous earth is an all natural, versatile, inexpensive, and non-toxic way to tackle many problems that crop up around the garden. Though you should take care not to breathe it in, using food grade diatomaceous earth from freshwater sources is safe enough to eat, and won’t harm people or pets if ingested.
Read on to discover the myriad ways to put diatomaceous earth to good use in your backyard.
1. All-Purpose Mechanical Insecticide
When viewed under a microscope, diatoms from freshwater sources are typically cylindrical in shape, with a glass-like texture, and have a jagged surface area covered in ribs, spines, pores, and ridges.
As pest control, diatomaceous earth works in two ways. When an insect crawls over diatomaceous earth, the notched surface of these tiny glassy cylinders cuts into its body, creating punctures and wounds that cause the bug to lose fluids. Because it is porous, DE also absorbs these fluids, drying the insect out. Although death is not instantaneous, bugs will typically succumb to their injuries within 24 to 48 hours. For large infestations, results will be noticeable within five days.
Diatomaceous earth is incredibly effective against a wide swath of insect types, but it does not discriminate between good insects and bad ones. For this reason, do not scatter diatomaceous earth willy-nilly around your yard.
To preserve a healthy ecosystem and protect your crops, it is best to use diatomaceous earth sparingly in the garden and to avoid applying it where it can impact ladybugs, bees, butterflies, green lacewings, wasps, and other beneficial bug populations. Use it only on severely affected crops, apply it close to the ground, and never use it on flowering plants. Spread it outdoors on calm days when the wind won’t scatter it across your garden and lawn. You can also cover up treated plants with burlap bags for a day or two and then wash the DE away with a hose.
2. Repel Slugs
With soft bodies made up of mostly water, slugs are voracious eaters that will prey on pretty much any organic material they come upon. They are generalists and will make a quick feast out of your plants and seedlings, gorging on leaves, flowers, lichens, mushrooms, and even earthworms and carrion.
Since they operate in slimy mucus, slugs are particularly prone to the desiccating effects of diatomaceous earth. Protect your plants by sprinkling it around the perimeter of your garden bed or around the base of individual plants. Diatomaceous earth readily washes away so be sure to reapply after each watering and rainfall.
3. Treat An Ant Invasion
Although ants in the garden are actually quite beneficial – they aerate the soil, feast on other insects, and as they march about, tend to pollinate flowers and scatter seeds – they can become problematic when they invade your home.
To treat indoor ants, first take note of where you have seen them and look for areas they might be getting in. Sprinkle diatomaceous earth along nooks and crannies in floorboards, baseboards, window sills, and any edges and cracks in doorways.
To apply it to walls and other vertical surfaces, make a spray by combining 4 tablespoons of diatomaceous earth with 1 gallon of water. Wet applications of DE will become effective once the water evaporates.
Keep watch for the next day or two to see whether they have adjusted their routes and apply fresh powder to new spots. After one month, clean up the diatomaceous earth and reapply if necessary.
Large anthills on your property could be contributing to your indoor ant problem so you may want to deal with it at the source. Use a shovel to dig into the anthill and expose the queen. Sprinkle some diatomaceous earth, stir it up with your shovel, and reapply. Scatter some DE in a 1-foot radius around the anthill.
4. Soil Conditioner
Though diatomaceous earth contains some minerals, it is much more effective as a soil conditioner in the garden or potting soil mixes. It’s porous and this helps the growing medium hold on to nutrients and retain moisture. A dash of DE in your soil will also help it drain well. It won’t harm beneficial microbes in the soil while protecting against soil dwelling insects like fungus gnats and root aphids.
To make a stellar water-retaining potting soil mix, combine 50% soil and compost, 25% coconut coir, and 25% diatomaceous earth.
5. Preserve Cut Flowers
Keep the beauty of your fresh cut flowers going longer by drying them out with diatomaceous earth.
First, hang them upside down in a dry spot for 3 days. Grab an airtight container and sprinkle a layer of DE along the bottom. Carefully place your flowers, ensuring none of the blooms or leaves are touching each other. Add another layer of DE and secure the lid. After 3 days, turn the flowers over and close up the container. Let it sit for 3 more days before removing them. Gently shake your cuttings to knock off the DE and arrange them in a vase for your viewing pleasure.
How to Use Diatomaceous Earth Safely
When shopping for diatomaceous earth, look for food grade varieties. Food grade DE is non-toxic and serves multiple uses.
In contrast, pool grade diatomaceous earth is heated to high temperatures, which alters the composition of the finished product. This type is used for water filtration, but is toxic to animals and humans, and is not effective as a pest control.
When working with diatomaceous earth, take care not to breathe in the fine dust particles during application. Although DE is generally safe, prolonged exposure can irritate the nasal passages and lungs. Those with respiratory diseases like asthma or chronic bronchitis should take extra precaution and wear a breathing mask.
Because diatomaceous earth is so absorbent, it can be drying to the skin. Don a pair of gloves to protect your hands from its dehydrating effects when working directly with it. For other applications, you can scatter DE using a spoon, a small duster, or a shaker bottle.