Gardening does not require an advanced degree, but some terms can leave you scratching your head. We all know you need great soil to grow great plants, but what is this magical loamy soil, those garden books say you should aim for?
Every gardener quickly learns that good soil is vital for a healthy, productive garden. Good soil means it has nutrients to feed the plants and a texture that holds water long enough for plant roots to access it, but well-draining enough that the roots are not sitting in water.
The best soil texture for growing plants is what is called "loam".
What is Loam?
The technical definition: Loam is soil that contains:
- less than 52% sand,
- 28-50 % silt, and
- 7-27% clay
However, if we had to measure that out every time we made a garden, there would be far fewer gardens.
Basically, loam is a soil comprised of almost equal amounts of sand and silt and a little less clay. Of the three components, sand particles are the largest. Sand does not hold onto moisture, but it provides good aeration. On the opposite end, clay particles are much smaller and easily compact. That makes clay a great material for building bricks, but not so great for allowing water, air, and plant roots through. Silt is the medium size particle, with better moisture retention than sand, but fewer nutrients than clay. Silt helps clay and sand mix together more easily, like tempering chocolate.
What Loam does for Plants
Loam is the ideal garden soil.
Its texture is porous, allowing water to flow through slowly enough for the plants to access it, but fast enough to avoid waterlogged, soggy soil. Loam is also nutrient rich
How to Create Loam
Although loam is a combination of sand, silt, and clay, adding sand to your clay soil, or vice versa, will not create loam.
Doing so will result in something like cement.
Creating a loose, loamy, fertile soil is an ongoing process that involves working organic matter into the soil, every year. The decomposing organic material creates the well-draining conditions plants need while attracting beneficial organisms that will help keep the soil healthy and alive.
Unfortunately, organic matter is quickly used up and needs to be amended each season. How much to add depends on how extreme your soil is, but for most soils, adding at least a two-inch layer of organic matter to the garden surface and working it into the top few inches should do it.
A word of caution: Buying soil in bulk can be a fast, easy way to get your garden or yard up and growing, but there is no standard or certification for soil quality. If you intend to buy soil, compost, mulch or other bulk garden material, know something about the company you are buying from. There are many excellent soil companies who stand behind their product. Generally, soil from excavation does not make ideal garden soil.