Exploratorium Science of Gardening: The Dirt On Dirt

Dirt gets no respect. When we're not ignoring it, we're walking on it, or doing our best to wash it off. Look up dirt in the dictionary and you'll find words like filth, impurity, and excrement.


	Minerals Humus Living critters Bacteria Actinomycetes Fungi Earthworms

You might even say that dirt gets treated like, well dirt. But gardeners know better. Gardeners give dirt the reverence it deserves, because they know that the right soil can make the difference between sparse, sickly plants and thriving bumper crops.

What is dirt, and what makes some dirt superior for gardening?

The stuff we call dirt—more formally, soil—is actually made up of two distinct types of material: minerals (the main ingredient) and much smaller amounts of organic matter; that is, living things and their decaying remains.


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