The term "soilless" has always confused me in regards to planting mix. The word "less" is a suffix that means without. Therefore, soilless, means without soil. Soil is found in the top layer of the surface of the earth, and contains organic matter, minerals, gases, liquids, and living organisms that support and balance life. So, unless you dug some dirt out of your yard and used it to germinate seeds or grow plants, you are not using true soil. If you have, however, purchased a bag of potting mix, peat moss, or garden soil, you have used soilless planting mix! Even if the label says it has soil in it.

A variety of components can be found in soilless mediums, such as bark, sphagnum moss, ground coconut husks, perlite, vermiculite, rock pebbles, sand, clay pebbles and volcanic rock wool, to name a few. Soilless mixes are ideal for indoor use, outdoor use, and for growing plants in greenhouses, growth chambers, or indoor growing tents. These mixes contain a variety of mediums designed for different plant types, and therefore, can be designed to work for a diverse population of plant species and a wide range of moisture regimes. Fruits and vegetable yields can be increased due to the opportunity of year-round production. The use of herbicides and pesticides can be greatly reduced or eliminated.

Soilless mixes often include one or more ingredients. This is because, when some are used independently, results are not ideal. Perlite, for example, dries out too quickly for plant roots when used alone, and will float. Peat moss can retain moisture very well when mixed with vermiculite, but dries out quickly alone and is slow to absorb water (becomes hydrophobic). Succulents and cacti prefer coarse, drier mixes, with sand and perlite for drainage. Garden and tropical type plants that require wetter roots, prefer finer mixes, with peat moss, coconut hulls, and vermiculite.

Prior to use, soilless components are typically sterilized. This kills any soil-borne diseases, or harmful bacterial organisms that may be present. The downside to this, is that beneficial bacteria/organisms are killed as well. Most mediums do not have an abundance of minerals in them and this is why proper fertilization is important. Check what type of fertilizer works best for your particular plant species. Desert plants will have completely different needs than garden plants. Sometimes, slow-release fertilizers are incorporated into mixes. Common fertilizer ingredients include nitrogen, phosphorus, and potassium, or NPK. If a label reads , 3-1-2, the nitrogen percentage is 3%, phosphorus 1% and potassium 2%. This is a solution suitable for hydroponic application. Solid fertilizers often have higher percentages, because when mixed in water, they decrease to liquid application rates. Nitrogen promotes green stems and leaves, whereas, phosphorus is required for root, fruit, flower, and seed production. Potassium helps form strong, fast growing stems. Other nutrients may be added too, depending on the requirements of the plant species.

Be your own scientist and experiment with several mediums on your own! Purchasing components separately and mixing in the percentages your plant needs, is the best route to go. Prepared soilless planting mixtures are not regulated by any state or federal agency, therefore, the exact proportions you are purchasing, are not listed. Labels will list ingredients in order of amount, but exactly what amount that is, does not have to be disclosed. The important factor is understanding the needs and environmental requirements of the plants you will be growing. Once the research is done, then you can use your own growing medium recipe, or purchase the most appropriate prepared soilless medium. Just give it a try! Soilless cultivation has the greatest potential to conserve water, reduce fertilizer use, reduce pollution, and reduce or eliminate the use of pesticides and herbicides. On top of all the benefits, its fun!

Author's Bio: 

D Everleigh is a retired plant biologist who enjoys growing plants, and teaching others how they grow. She is passionate about encouraging people of all ages to experience gardening, and helps run a website called smallgreenhousesetc.com