If you’re interested in gardening, landscaping, propagating succulents, or anything in between, you’re going to have to start with the basics: dirt.
Besides a nuisance under your fingernails and the occasional juicy gossip, what is dirt? What most people categorize as dirt is actually a number of different things: soil, humus, compost, and fertilizer to name a few of the most common. Here are the differences between these crucial types of plant food:
Soil is absolutely teeming with life and nutrients-- in fact, soil itself is considered a living thing! It’s usually dark and moist, as it must contain water in order to support the symbiotic food web thriving within. And if by “food web” you think I mean an entire ecosystem beneath your feet-- you’re right on the money. Within soil there are all sorts of microbes (such as bacteria and protozoa) as well as chemical reactions, earthworms, beetles and more. Decomposing material helps to feed the smaller organisms (microbes), which feed the larger worms and insects. The earthworms and insects help by both creating their own waste and by aerating the soil-- introducing oxygen into this mix is crucial to keep it healthy, like any living thing.
Sidebar on microbes: These decomposers are the same types of protozoa and (friendly) bacteria found in our guts. They help break down nutrients to help us digest our food and absorb nutrients-- and they help plants do the same.
While not technically dirt or soil, humus is the organic material within soil that helps feed the surrounding plants. It is the byproduct of the microorganisms, like protozoa, after they break down the organic structures like leaves. Humus is extremely dense in nutrients and will help your plants eat well and thrive! Humus can be artificially created with a well-crafted compost pile.
Which brings us to compost! Want good soil and humus? You don’t have to wait for the leaves in your yard to decompose into your garden-- you can start a compost pile now with the food remnants in your kitchen, some plant trimmings, and some good ol’ TLC. Compost piles begin as decomposing organic and natural material, think banana peels, eggshells, potato skins, etc. With sufficient water, oxygen, and organic matter, your compost pile will start churning out nutrient-rich humus in no time. If you'd like to start home composting, these resources from Sonoma County's Zero Waste Initiative or this guide from Marin County dive deeper.
If you do not have the time, space or patience to create your own compost, there are plenty to try out from your local nursery. We've tested dozens of different composts in our test garden, and the plants have informed us that a mushroom blend is their favorite. We would be happy to provide you with some compost if you are within 50 miles of our organic nursery here in Santa Rosa, CA.
So where does fertilizer come in to all this, you ask? Many familiar brand name fertilizers are largely synthetic not focused on overall soil health. While compost makes soil healthier, synthetic fertilizers are designed to feed the plants directly; they don’t do much for the soil. Fertilizer can be helpful for specific problems or deficiencies your plants are experiencing, but they have strong effects on gardens and too much of them can result in more harm than good. You can think of it this way: compost is like a healthy, nutritious, varied diet, whereas fertilizer is like a dietary supplement. If you are calcium or iron deficient, you can take a supplement to correct this, but remember a healthy diet is still of utmost importance.
However, it’s possible to purchase or make your own organic fertilizers out of nutrient-rich, natural materials. Finely ground egg shells or coffee grounds, for example, can be added to your garden soil. Fish and kelp emulsion provide a natural source of essential minerals and also increase microbial activity. They will also treat specific deficiencies, but they will do this by enriching the soil.
For those of you still wondering, there is still such a thing as dirt that is not soil or compost. Though the definition is still sometimes disputed, the generally agreed upon meaning of dirt is the lifeless version of soil. This means that it is devoid of all aforementioned microbes, organisms, insects, and moisture-- due to these absences, it’s also typically lighter in color and more crumbly or sandy and it has little to offer surrounding plants besides a place to rest their roots.