What Makes Good Potting Soil?

Good potting soil enables plants to flourish.

Good potting soil can make your planting project easier and more enjoyable because it creates an environment in which your plants can thrive. Soil from your garden typically is too compacted to use when growing plants in containers, particularly houseplants. Good potting soil features several materials that essentially strive to mimic nature's healthy earth to stimulate plant growth.

Fertilizer

A good potting soil must include key plant nutrients, such as nitrogen, phosphorus and potassium. Nitrogen helps plants make food through the process of photosynthesis and boosts seed and fruit production in plants. Phosphorus helps plants mature and handle stress, while potassium helps build protein and improves fruit quality in plants. These nutrients are available through a fertilizer included in packaged potting soil. The fertilizer that bears these and other micronutrients such as zinc, boron and iron typically is a slow-release type, which allows the plant you are growing to receive the fertilizer's long-term benefit.

Organic Matter

Organic matter also is present in quality potting soil. For example, potting soil mix might include ground bark, worm castings, compost or sphagnum peat moss. Because acidic peat often is a component of potting soil, potting soil tends to be acidic. Adding lime is an easy way to raise the level of acidity to a pH level that is suitable for most plants. Although organic matter such as peat moss does not contain nutrients, it easily absorbs nutrients present in the potting soil and releases them to your plants as the plants need them. This prevents the loss of nutrients through leaching. Organic matter in potting soil provides an appropriate balance of water and air for plants.

Vermiculite

Another component of good potting soil is vermiculite. Vermiculite is a silicate material critical for improving soil drainage and aeration. When combined with composted pine bark or peat, vermiculite helps young plant roots to become established and also stimulates quick root growth. Like organic matter, vermiculite helps plants with moisture and nutrient retention and simply releases plant food to plants when required.

Perlite

Perlite additionally makes up good potting soil. Perlite is a volcanic material heated to 1,600 degrees Fahrenheit. This lightweight material creates tiny air tunnels in potting soil mixes, which let oxygen and moisture flow easily to plant roots. This is a critical provision because a plant absorbs 98 percent of its oxygen through its roots. Nutrients and oxygen can cling to perlite particles because of the particles' unique shape. In addition, perlite's granular nature allows for quick drainage of excess water from the plant, which prevents problems such as root rot.

References

• Plant Care: Potting Soil Benefits
• Maine Organic Farmers and Gardeners Association; The Dirt on Potting Soil; Craig Idlebrook; 2006
• North Carolina Department of Agriculture: Plant Nutrients
• Canadian Sphagnum Peat Moss Association: Gardening Tips
• The Vermiculite Association: Horticultural Vermiculite
• Perlite Institute Inc.: Indoor Gardening With Perlite