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https://extension.psu.edu/homemade-potting-media

Many cost conscious home gardeners and do-it-yourselfers are often looking for cheaper ways of growing plants for home and garden use. One way to achieve this may be by making homemade potting media rather than purchasing pre-made materials at garden centers and home supply stores. Although purchasing the base ingredients and developing your own mix may not result in a cheaper mix, it does offer the opportunity to be creative and to modify mixes for specific goals or plants that you feel would make a media better for your situation. The following information will provide you with a basic understanding of potting media ingredients and steps for making a homemade media from scratch.

Potting media, which has a coarser texture than garden soil, is commonly used in container gardens and in trays for sowing seeds. Ingredients recommended for potting media have changed over the years as research conducted by professional horticulturists has identified components that are beneficial for sowing seeds and plant growth. Before the mid-1900's, soil-based potting media was commonly used; however, in recent years, peat-based soilless mixes have become more popular. Many ingredients are now available to gardeners who choose to create a homemade potting media instead of buying one from a retailer.