Soil, Compost & Mulch: What’s the Difference?

Now that we’re starting to look forward to spring here in the Salt Lake City area, it’s probably time to start planning for spring planting and what you’ll be putting into your garden this year. Ever wondered about the differences between soil, compost, and mulch, and how each of these products can be used in your home landscaping? Here is a look at the major differences between the three terms.


Soil is kind of a loose term because in the landscaping world it is often used simply to refer to dirt. There are two major types of soil you’ll hear about in the landscaping realm: garden soil and topsoil.

Garden soil

Healthy soil is the basis for growing healthy plants, and this is where garden soil typically comes in. Before it’s time to plant, garden soil is turned with existing soil in order to improve overall soil quality. It isn’t necessarily much different from what soil already exists in your garden naturally. When you purchase garden soil, you’ll want to be sure that the materials it contains will blend well with your existing garden and that these materials will be compatible with what you are trying to grow.


While on the subject of soil, you’ve probably heard the term “topsoil.” What sets topsoil apart from garden soil? Essentially, topsoil is reserved for applying on top of garden soil. This top layer of soil contains a calculated mixture of clay, sand, and silt and is rich in the nutrients that your plants need to survive and grow. Specific blends of topsoil will vary depending on which plants they are supposed to nourish. Most layers of topsoil are between 5 and 12 inches deep. Some people use topsoil as an all-purpose product for filling holes and leveling planting beds, as well.


Compost is, technically speaking, organic animal and plant matter that has decomposed. It is not a replacement for topsoil; rather, it should be tilled into soil in order to improve soil quality. Compost is rich in nutrients, and it can even make nutrients that are already in the soil more readily available to plants.


Mulch is applied to the soil’s surface in order to discourage weed growth, insulate the soil, retain moisture in the soil, and reduce erosion. You can think of it as a protective cover for your soil. It can be made from either organic or inorganic materials, though some will only use the term “mulch” to refer to mulch made from organic materials. Some of the most common organic materials used in mulch are shredded wood, wood chips, small pieces of tree bark, shredded leaves, grass clippings, and straw. Mulches made from wood materials are often dyed for a decorative look. Some inorganic materials used as “mulch” include stones, gravel, and landscaping fabric.