When choosing soil for a potted plant or planting bed, understanding the basics of what makes good soil is an important step toward achieving planting success. Along with nutrient properties and the ability to hold nutrients, soil must also have the right amount of drainage for the type of plant. Solve drainage problems by adjusting soil properties using additives.
Good drainage is an essential part of a healthy growing environment for most plants. Proper drainage helps prevent diseases that thrive in damp, standing water. Choosing soil with good aeration and drainage harbors stronger root systems than those that develop in poorly drained growing mediums.
Soil mixtures with poor drainage usually have an excess of clay or broken-down organic material causing tightly packed soil that allows little air and water through. When soil becomes too dense for proper plant growth, it needs a soil additive to adjust its properties. In lawns, a buildup mainly composed of dead grass--called thatch--may also contribute to drainage problems.
Signs of a drainage problem include long-standing puddles after watering, musty smells, plants that wilt even though the soil is wet and an excess of flies or gnats. On a lawn, poor drainage can cause brown patches, weeds or lawn death. Dense and isolated patches of dandelions on a lawn can indicate poor drainage in that area. Soil testing, usually performed at agricultural centers, can determine the contents of soil and possible causes of poor drainage.
When working to improve soil drainage, the larger the particles of the soil additive you use, the better the drainage. Soil that's mainly clay can be improved by adding sand or mineral-based substances. Common mineral additives used to increase soil drainage include vermiculite and perlite.
Decreasing Soil Drainage
Soil with good drainage has good permeability. Good permeability means water and air easily pass through the soil. If soil is too permeable, it may not hold water well, making it unsuitable for plants that require regular waterings and even soil moisture. Clay is a soil material that holds water well. Adding clay to a soil mixture that drains too easily reduces its permeability, helping it hold water and dry more slowly.