I think in all of gardening, I love soil as much as what grows in it. That's because I know how important healthy soil is to growing robust, productive, pest- and disease- free plants.

Soil is more than just dirt or a place where roots live. It's the warehouse for nutrients, minerals, oxygen and moisture. It's also habitat to billions of beneficial bacteria that not only improve plant health, but also fight off disease organisms.

You'll find that gardeners rarely refer to soil as simply dirt. They understand the difference between the stuff you dig up in your backyard vs. the "black gold" that consists of compost, manure, decomposed organic matter and millions of beneficial microbes.

Converting dirt to soil is an attainable goal, even when starting with a heavy clay or very sandy base. Within this context, understanding three commonly used terms - texture, structure and tilth - should get you on your way to a healthier garden.

Texture refers to the relative percentage of sand, silt and clay in the dirt. Ideal soil has an equal amount of each. The description we hear most often is that the soil is loamy. Great texture allows plant roots to spread, moisture to be retained yet drain well and essential air pockets to exist between soil particles.

Next is soil structure, or how the components of sand, silt and clay fit together. Good structure is evident when the soil holds together if squeezed but breaks apart or crumbles easily when disturbed. Adding plenty of compost and aged manure does the trick.

Soil that has good tilth is loose enough to allow for adequate drainage, yet dense enough to retain moisture long enough for plant roots to use it. This is why garden soil should contain neither too much sand nor too much clay.

The key is to know from which extreme you are starting. If soil is too dense, then loosen it up by adding gritty organic material like composted bark. For soils that are too loose, you want to increase the water-holding capacity. Peat moss is a popular option, but compost works, too.