The dirt on soil products

6/26/2013

Every time I go to the garden center, I’m amazed at the number of soil products available. There are types just for specifically starting seeds, mixtures for potting and containers, transplanting blends, general garden soil or even specialty concoctions for narrow categories such as cactus, violets and succulents. And you can buy products with fertilizer and moisture-retention ingredients mixed in.

Fortunately, the organic gardener isn’t completely passed over in the sea of choices, as there are a few options here, too.

Who would have thought that what some people still consider dirt has evolved into such designer products?

Astute gardeners can appreciate that all store-bought soil is not created equal, and for good reason. But do we really need so many options? I believe that no, we don’t need so many choices. Yet branded soil lines seem to be some of the hottest products in home gardening today. You can credit that to good marketing, consumer confusion and very busy lifestyles. If you look at the ingredients on most of these products, you’ll be surprised to find they all include most of the same components.

When it comes to labeling, one important term to note is the difference between “soil” and “soilless” blends. Soilless blends are used for starting seeds and seedlings. These mixes are usually a combination of peat moss, perlite and vermiculite. They are called “soilless” because they do not contain material commonly found in typical soil products that might have pathogens that could harm or kill tender seedlings at such an early stage. These products have been pasteurized, or heated to a very high temperature, so that any potentially harmful ingredients have been killed. They are also the lightest in weight and density, which is necessary for giving seeds the best chance of a good start. Soilless mixes are indeed the best choice for starting seeds and a great product for their intended purpose.

The rest of the soils, including potting or container mixes, usually include peat moss, perlite and “composted natural products.” This last component varies from region to region. It depends on where the product was made, and what was available. Consider it a catchall phrase. The biggest variable is the percentage of each. These products are designed to be light enough to allow for good drainage, yet maintain some water-holding capacity. This is a good combination for anything planted in a container.

Container mixes, as they are commonly known, are another category of bagged soil. Manufacturers add materials such as slow-release fertilizers and water-holding polymers that absorb water and make it available to plant roots over extended periods. For container plants, that’s especially important. They dry out far more quickly than plants in the ground, so they need to be watered much more frequently. Consequently, any nutrients within the container tend to be washed away more quickly, as well.

In my opinion, the biggest advantage to the wide range of specialty soils available today is convenience. To be sure, they are fine products. If you’re looking to save time or don’t want to think about it, designer soils are just what you need. But a basic understanding of soil, plant needs and fertilization can go a long way in creating your own custom blend -- and save a few dollars in the process.

It’s certainly not as convenient, but I find it to be a lot of fun and an excellent way to have a better understanding of the important role that having the right soil plays in the success (or failure) of your plants.

(Joe Lamp’l, host and executive producer of “Growing a Greener World” on PBS, is an author and a paid spokesman for the Mulch and Soil Council. Contact him at email@joegardener.com. For more information, visit www.GrowingAGreenerWorld.com. For more stories, visit shns.com.)