Premixed media is common for greenhouse growers, designed to achieve recommended porosity and water retention. Soilless ingredients are commonly used, according to the Center for Agriculture, Food, and the Environment at the University of Massachusetts, Amherst, including "peat moss, vermiculite, perlite, shredded coconut husks (coir), or composted materials plus starter nutrients and a wetting agent." Common field dirt is not recommended, due to the high possibility of disease and weed seeds in non-sterile or non-pasteurized soil. In addition, common soil is not recommended for container gardening because it does not provide the required aeration, draining and water holding capacity required for plant growth.
Commercial mixes with added biological fungicides are available, and compost-based formulations suitable for organic growing are also offered. Any growing medium should be regularly tested, and pH monitoring is important to assure optimum nutrition for the plants. In addition to routine soil tests, growers should regularly check the electrical conductivity and soluble salts of the growing media. Greenhouse growing is increasingly scientific, and even a hobbyist should be aware of the unique requirements for successful greenhouse growing. Many state universities or their extension agencies will perform pertinent soil and water analysis and evaluation.
