Buzz
Before I became a gardener, I couldn't differentiate between the various soil mixes. Whenever I needed to fill a planter, pot, or patch of land, I simply grabbed the most affordable bag of whatever from the big-box store. You know the aisle—piles of colorful bags with hardly any details to help you distinguish them. You could learn through trial and error like I did, or you could avoid my mistakes by reading on.
What exactly is soil?
Soil, as we know it, is essentially just dirt: it's a mix of decomposed organic matter like fallen leaves, twigs, branches, and anything else that has decayed in the ground, along with organisms living within the soil itself. Typically, soil also contains clay and/or sand, along with rock particles. The ideal soil for plants will have nutrients, sufficient space for the roots to spread easily, and moisture—but not too much. These nutrients must be balanced; otherwise, plants struggle to absorb them. If the soil is too compact due to clay, roots can't grow properly, and the plant may become stunted. If there's excessive sand, the soil will fail to retain enough moisture or nutrients. The growing conditions in a pot or planter differ greatly from those in a raised bed or in the ground.
Your yard's topsoil probably isn't ideal
When I first started gardening, I imagined simply digging into the soil in my yard and planting. I envisioned plunging a spade into the garden and uncovering rich, loamy soil teeming with worms. The reality is that your yard's soil is likely subpar, due to both the nature of the local dirt—perhaps it's overly sandy or full of clay—and a lack of nutrients over the years. That dirt is considered topsoil, and in most cases, topsoil isn't high-quality soil. It contains undecomposed materials, like leaves and twigs, making it prone to waterlogging. Unless the soil has been covered by years of mulched leaves, it probably lacks enough organic matter to provide nutrients or good soil structure. Topsoil mostly serves as a filler material—used for filling spaces during construction. In most cases, you'll need to improve it with additional nutrients and other organic materials.
Check out local rock yards for garden bed mixes
If you're setting up a brand-new garden, you might want to consider a garden bed mix, which you can find at your local big-box store. However, this isn't the most budget-friendly option. The bags are sold by the cubic foot, but you'll need to think in cubic yards. Many local rock yards offer three-way or four-way mixes, which typically contain topsoil, compost, sand, and other organic materials. You can arrange for delivery, and then it's just a matter of moving it—probably by wheelbarrow—from the delivery site to your garden beds.
In most urban areas, you can purchase high-end organic garden bed mixes that are marketed as premium quality. Personally, I don’t believe they're worth the price. I've never seen better results from these expensive mixes. The soil you add to your garden is only the starting point—you'll need to amend it every year, often multiple times. The delivery of soil is just the foundation to begin with.
Compost is not the same as soil
As you dive into gardening, you'll constantly hear about how crucial nutrients are for your soil, with compost often cited as a source of those nutrients. You might wonder, since compost resembles soil, why not just use it to fill an entire garden bed? The key is understanding what compost actually is. When organic matter like leaves, wood, plants, kitchen scraps, animal waste, or compostable materials decompose, it becomes a nutrient-rich substance that looks similar to soil. While compost is packed with nutrients, it lacks structural integrity—it's too loamy and full of humus, which is why it requires sand and clay to balance it out. Typically, compost is added to the soil once or twice a year, simply placed on top of your garden beds. The nutrients then filter down into the soil through watering and rain. Since your garden beds lose volume each season due to erosion, compaction, and plant removal, compost helps replace that lost volume.
In many urban areas, compost is available at low cost or even for free. The city collects leaves or green waste and turns it into compost, which is then offered to residents. It's worth checking with your city to see if they have such a program. This is the compost I use exclusively.
Planters require a specific planting mix
Different plants, from orchids to cacti, require different potting mixes. These mixes are primarily designed to manage varying moisture levels, and often contain a slow-release fertilizer. Most planters have drainage holes or are made of under-fired terracotta that allows moisture to seep out. To compensate for this, potting mixes include materials like vermiculite, perlite, coco coir, or peat moss—organic substances that help retain moisture. (By the way, you should try to avoid using peat moss, as it's a diminishing natural resource, and instead opt for coco coir.) You may also notice colored granules in the mix, which are typically the slow-release fertilizers that feed the plant over time. Since these fertilizers don't last indefinitely, potting mixes should be refreshed annually by mixing them to break up compaction and adding new fertilizer, such as Osmocote.
Seed-starting mix is like a cozy blanket for your seeds
When starting seeds, it's essential to create the right conditions. The soil should be light, fluffy, and airy to promote root development. It also needs to be fine enough to fill the cells of a seed-starting tray. Because delicate seeds and seedlings can be harmed by fertilizer, seed-starting mix typically doesn’t contain any added nutrients. While potting mix can work in a pinch, seed-starting mix is designed to give you the best possible results and is always purchased in bags.
Select the right soil for a strong start
No factor is as crucial in gardening as healthy soil: soil that drains well, holds the right nutrients, and retains the proper moisture levels. Ideally, it should be free of weeds and harmful pests like slugs and snails that can damage your plants. Surprisingly, a lot of this can be managed by you.
