Worm Castings vs. Compost: What's the Difference and When to Use Each?

If you're already composting in your backyard or buying bags of compost from your local nursery, you might wonder - do I really need worm castings too? The answer is yes, and here’s why.

While compost and worm castings are both fantastic for building soil health, they serve different roles in the garden. Think of them as teammates - not rivals - in your quest for thriving plants and rich, living soil.

What Is Compost?

Compost is decomposed organic material made from food scraps, leaves, grass clippings, and other natural matter. Whether you make it at home or buy it in bulk, compost is used to:

• Add organic matter to soil

• Improve texture and drainage

• Feed soil microbes over time

It’s a great way to recycle nutrients - but compost varies depending on what you put in, and it isn’t always rich in plant-available nutrients.

What Are Worm Castings?

Worm castings are the digested version of compost, made when earthworms break down organic matter in their gut. This process produces a finished product that is:

• Microbially active

• Nutrient-dense and immediately available to plants

• Free of pathogens and weed seeds

• Uniform in texture and pH-balanced

Worm castings act more like a natural fertilizer, while compost is more of a soil conditioner.

Key Differences at a Glance