Soil is the unsung hero of a garden. Often regarded as just dirt, it takes a backseat to the glamorous flora of a garden but it's always hard at work below the surface.
Soil is the very foundation on which your plants feed and thrive, serving as a medium for housing beneficial microbes and earthworms and a reservoir for delivering vital moisture and nutrients to the roots. When you garden, you're actually growing the soil, rather than the plants. No matter how much money you've spent or how much work you've put into sowing, weeding, watering, and tending your garden, your greenery will never reach their full potential if the soil is weak.
Thus, knowing your native soil type (sometimes referred to as topsoil) is important for determining what plants, shrubs, and trees will grow successfully in your garden. Each type has its own blend of minerals, organic matter, and inorganic matter that makes it more hospitable to certain types of plants. It helps to understand the characteristics of the soil you have to work with, so that you can amend it as needed to create the ideal growing medium.
Sand is the coarsest of all the soil types and feels gritty and loose. It's easy to cultivate, warms up quickly in spring, and drains very easily. However, its ability to drain also makes it more difficult for sandy soil to retain nutrients, which are often washed away. Since moisture runs right through sand, it dries out fast — a plus for drought-tolerant plants, but a drawback for those with substantial water needs.
Ideal For: Mediterranean herbs such as rosemary, sage, oregano, thyme, and marjoram, which favor dry conditions and low fertility; root vegetables such as carrots, turnips, and parsnips; fruits such as grapes, blueberries, and strawberries; flowers such as California poppies, daylilies, and coneflowers; bulbs such as crocuses and tulips; and desert plants such as grasses and succulents.
Commonly found on floodplains, silt is finer than sand and silky smooth to the touch. When wet, it feels slick and soapy. It's very fertile and holds moisture well — sometimes too well, so it's an ideal soil type if drainage can be managed in the garden. Though silt is easy to work with because of its texture, its characteristics can make it more prone to compaction and poor aeration.
Ideal For: Plants that like having their feet wet, such as hostas and ferns; flowers that prefer soil on the heavy side, such as swamp milkweed and Japanese irises; and fruit and vegetable crops that thrive on nutrient-rich soil (though gardeners should take care to ensure proper drainage and pest management, as continually damp soil can encourage these problems).
The heaviest of all the soil types, clay feels clumpy and sticky when wet, and compacted and rock hard when dry, both of which make it difficult to work with in the garden. Because so little air passes through its particles, clay is slow to warm in spring and thus is best suited for a raised bed garden. On the upside, it retains moisture and nutrients very well, so gardeners can still make it work with some proper conditioning.
Ideal For: Plants that thrive in heavy soil, such as snowdrops, camellias, roses, rudbeckia, goldenrod, canna, and coreopsis. On the edible front, vegetables such as summer squash, winter squash, okra, and chard tolerate clay soil, and shallow-rooted crops such as spinach, lettuce, onions, and corn do well as they don't need to reach deep into the earth.
Loam is the type of soil every gardener dreams of, comprised of all the best qualities of sand, silt, and clay. This balanced blend gives it a slightly damp, finely-textured feel that drains well while still retaining moisture. When wet, loamy soil is smooth, partly gritty, partly sticky, but crumbles easily. It is full of nutrients and the easiest of all the soil types to cultivate, whether wet or dry.
Ideal For: Just about everything! Loamy soil is highly productive, but only stays that way with careful management to keep it in tip-top shape. That means cover cropping and forking in fertilizer to replenish its nutrients, adding mulch and compost to retain its structure, and practicing crop rotation every season to reduce soil depletion and prevent plant diseases.
How to Tell What Type of Soil You Have
Grab a handful of wet soil and gently compress it in your fist.
- If it feels gritty and falls apart right away when you open your hand, you have sandy soil.
- If it feels sticky and holds it shape in a ball when you let go, you have clay soil.
- If it feels smooth and holds its shape for a short period of time, you have silty or loamy soil. Silt, however, will stay wet longer than loam.
What About Soil For Container Plantings?
Potted plants require a special type of soil that's not actually soil at all. Sold in garden centers as potting mix or potting soil, this growing medium is a blend of organic matter formulated to assist with aeration and drainage while holding as much moisture as possible. Common ingredients in potting mix include peat moss (or coconut coir), perlite, vermiculite, bark fines, sand, and sometimes compost or slow-release fertilizer.
Potting mixes are often specific to the type of plant you're growing. For example, a mix for cacti and palms will be sandier than one made for vegetables and herbs. Whatever you do, don't use your native soil for a container plant. Native soils are typically too heavy for containers, and will make watering and growing much more challenging.
Expert Tip: Supplement with store-bought compost or garden soil. If you're not blessed with the Holy Grail that is loamy soil, you can improve your soil structure by mixing it with compost or garden soil. If you're sourcing the compost from a farm or feed store, make sure it's well aged so it won't burn your plants. "Garden soil" is actually a commercial blend of different soils, fertilizers, and organic matter that create a nutrient-rich — and sometimes plant-specific — growing medium.