Garden Soil 101

Just because you have a garden doesn't mean you have good garden soil. Luckily, bad garden soil can be improved. Here's how to understand what your plants are growing in.

It may take a little green thumb to grow a garden, but what growing a garden mostly takes is good garden soil. As with many things, bad garden soil can be made better, but truly good garden soil needs constant tending to provide the best base for your plants, trees, and shrubs. Luckily, garden soil is easy to understand. Here are the most frequently asked questions when it comes to dealing with tricky garden soil.

What Are The Best Garden Soil Components?

Garden soil is made up of three particle sizes: the smallest particles are clay, the midsize particles are silt, and the largest particles are sand. The proportions of those three components—referred to as a soil's "texture"—determines how easy your garden soil is to work with and how well it will support your plants. A fine-textured soil has a lot of clay; a coarse-textured soil is sandy.

If your soil has too much clay or too much sand, there are simple ways to fix it. You can improve clay soil in your garden by adding organic matter, or compost. Tilling in 2-3 inches of compost allows soil to hold more water and nutrients. The chemical properties of compost also help prevent soil compaction. If you are having trouble with the clay soil in your yard, creating your own rich, organic garden soil will help alleviate these issues.

What Type of Soil Do I Have?

Each type of soil comes with its own set of pros and cons. Sandy soil is nutrient-poor and dries out quickly, so it requires more water and fertilizer. Despite these traits, it does have excellent drainage. Clay soil will be sticky when wet (making it hard to till) and drains slowly, but it holds a lot of water and nutrients, which is good for plants. Silt is intermediate in these qualities. Ideally, soil should include a significant amount of all three components, which will give it the beneficial properties of each. Knowing these characteristics, you can easily determine what kind of soil you have.

What is Soil pH?

Soil pH is a measure of how acidic or alkaline your soil is, indicated by a number between 0 to 14.0. A pH of 7.0 is neutral—neither acidic nor alkaline. Below 7.0 is acidic, or "sour", and above 7.0 is considered alkaline, or "sweet." Garden soil pH levels rarely run below 5.0 or above 9.0, and in a majority of cases are between 6.0 and 8.0. Within that range, most garden plants will perform reasonably well; however, there are some exceptions.

Acid-loving plants like blueberries, azaleas, and rhododendrons prefer a pH of less than 6.0 but will usually tolerate a pH up to 7.0. If your soil's pH is alkaline, you may need to make it more acidic in order for such plants to thrive. Certain hydrangeas need acidic soil to turn their blossoms blue. There also are plants that are called "lime haters." These plants don't necessarily need acidic conditions but can be severely affected by overly alkaline conditions (limestone is extremely alkaline).

How Do I Change My Soil's pH?

Lowering your plant's pH can be accomplished by adding acidifiers to the soil. Sulfur is a potent acidifier, and just adding lots of compost can lower pH, too. Pine needle mulch will gradually lower pH as well, though it takes years to do so. Contrary to popular belief, gypsum does not directly lower pH.

On the other hand, adding lime to soil is the most effective way to raise pH levels. Many people add lime habitually to their gardens, but there's no reason to do so unless pH has become excessively low (below 5.0). This sometimes happens in lawns but seldom in garden beds. By giving your soil what it needs for optimum performance, your plants will thrive like never before.

Editor's Tip: It's important to remember that soil has a tendency to bounce back to its original pH, and that repeated applications over several years may be necessary to make the pH changes stick.

Do I Need a Soil Test?

You'll need to test your garden soil to determine soil pH. Simple DIY test kits are sold at garden centers for a minimal cost. A more accurate pH reading, and a great deal of other information, can be obtained with a professional test, which many garden centers and cooperative extension offices offer for a reasonable fee. In practice, keeping pH within reasonable limits and amending regularly with compost will almost always give good results. But if plants seem to be suffering for no apparent reason, a complete soil test may help you determine the problem.


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