Mulch vs. Compost: Which Should You Use?

A very common mistake in gardening and landscaping is confusing the purpose of mulch with the purpose of compost. While both are organic materials placed in garden beds, they serve two entirely different functions.

Understanding when and how to use them will save you money and protect your plants.

What is Compost?

Compost is a nutrient-dense, decomposed organic matter. It looks like very rich, dark soil. Its primary purpose is to feed your plants.

When you mix compost into your soil, you introduce beneficial microbes, improve soil structure (especially in heavy clay or sandy soils), and provide a slow-release source of nitrogen, phosphorus, and potassium.

• When to use it: When planting new beds, amending poor soil, or topdressing lawns.
• How much to use: Usually a 1 to 2-inch layer tilled into the top 6 inches of soil. Calculate exactly how much you need with our Compost Calculator.

What is Mulch?

Mulch is an umbrella term for a protective layer applied to the surface of the soil. While it can be organic (like shredded wood bark, pine straw, or grass clippings), it can also be inorganic (like rubber or gravel).

Its primary purpose is to protect the soil.

Mulch blocks sunlight to prevent weed seeds from germinating, acts as insulation to regulate soil temperature (keeping roots cool in summer and warm in winter), and dramatically slows moisture evaporation.

• When to use it: Every spring and fall, layered on top of existing beds.
• How much to use: A 2 to 3-inch layer is standard. Over-mulching can suffocate plant roots. Calculate exactly how many bags or yards you need with our Mulch Calculator.

The Winning Combination: Layering

If you want the ultimate garden bed, you don’t choose between them—you use both in sequence.

1. First Layer: Apply 1-2 inches of compost directly to the soil surface to feed the roots.
2. Top Layer: Apply 2-3 inches of wood mulch directly over the compost.

The mulch will lock in the moisture and protect the compost from washing away in heavy rain, while slowly breaking down over the year to add even more organic matter to your soil.