Do you know the difference between soil and dirt? Learn which type of soil or medium is the best bet for your gardening needs.
By Shelley Wigglesworth
Apr 11 2022
Do you know the difference between soil and dirt? Do you know what makes up vermiculite and perlite? And when should you use compost? Read on to learn how to distinguish between the basic and not-so-basic types of growing media, and find out what type of soil or medium is the best bet for your gardening needs.
Dirt: Dirt is often rocky, silty, and void of any beneficial nutrients and microbes that healthy plants need. If you add water to a handful of plain dirt, it will not compact well, if at all. Because of these qualities, dirt does not make a good gardening medium.
Soil: Soil, on the other hand, is the perfect gardening medium, as it is rich in nutrients and microbes, and when scooped up in your hand, it will clump or form a loose ball easily — often without water being added. When red-wiggler or earth worms are present in soil, it’s a sign of fertile ground in which to grow plants. Worms will not thrive in dirt.
Compost: Compost is the end product of decaying plant matter and should only be used when it has “cured” — i.e., broken down completely. Compost that has cured will look dark and have a rich, earthy smell. It must show no signs of the previous organic matter that it is made up of. If decaying vegetation is still visible in the compost, it has not yet finished breaking down and the nitrogen level in the compost is too high to safely apply on or around plants. If the compost is used at this point in the breakdown, it will burn and most likely kill plants.
Composting times vary depending on methods used to compost, so when in doubt, allow the compost to set longer or test a bit in a small potted plant before amending large quantities of garden soil with compost. Compost should be added yearly to gardens to keep the soil rich with nutrients.
Peat Moss: Peat moss is decomposed and dried organic matter containing some form of non-living or petrified sphagnum moss. It is great for absorbing water and gradually releasing the water with minerals from the peat. Peat moss is great to add to compost and soil mixtures to lighten its density, reduce watering requirements, and lower the overall pH.
Perlite: Perlite is the result of volcanic minerals (obsidian) being pulverized and heated. It is added to soil to make the mixture more porous and is also used as a medium in soils made for drought tolerant plants, such as cacti and succulents.
Vermiculite: Vermiculite is an altered form of the mineral mica, which is heated to very high temperatures to make the vermiculite. Vermiculite is added to soil mixtures to increase the soil’s porousness and, like perlite, is often used with drought tolerant plants.
To create a simple and healthy soil mixture for growing a variety of plants, combine 4 parts gardening soil with 1 part compost, ¼ part peat moss, and ¼ part vermiculite or perlite. Mix well!
Now that you know the difference between soil and dirt, and a bit about other common gardening media, you’re one step closer to being a master gardener! Happy Planting!
This post was first published in 2013 and has been updated.