If you've ever planted a houseplant or had a container garden, you may already be familiar with potting soil. Most gardening experts caution that container gardeners should only use potting soil for container gardens, rather than using dirt. That's because potting soil is actually not soil at all, but a mixture of peat moss, bark and perlite. Unlike dirt, potting soil contains no microbes that could harm a plant with confined roots. The use of potting soil may date back to prehistoric times.
Around 1160 BC, the ancient Egyptians began growing the first shrubs and potted plants in containers. These early container gardens were a handy way to keep rare plants alive in the barren deserts, particularly plants used in aromatic oils or dyes. Gardeners also found it convenient to transport lush greenery along with rulers as they traveled up and down the Nile River. These early plants were placed in pots along with rich, organic soil from the banks of the Nile.
The most famous large scale container gardens were the Hanging Gardens of Babylon. Nebuchadnezzar II built the hanging gardens to re-create the lush mountainous terrain of Media in the barren desert as a gift for his wife, Amyitis. The gardens were filled with plants from her native land, and were irrigated almost constantly. It is likely that the gardens were filled with some ancient Babylonian form of potting soil, which would have mimicked the soil conditions of Media rather than the barren soil of Babylon.
The mention of soil amendments in containers was in the Roman period. The Roman Emperor Tiberius had a greenhouse constructed out of mica to grow cucumbers during the winter months. This early greenhouse was heated with manure that was mixed into the soil. The cucumbers were planted in containers that could be wheeled into the outdoor sunshine during daylight hours, and then returned to the greenhouse at night.
In China, the practice of container gardening was flourishing Independently of the western gardening evolution. Around 220 AD, Chinese emperors during the Han Dynasty built miniature forests in trays. Because the plants' roots were confined to small pots, these early gardeners may have used specially mixed soils to make the plants thrive. This practice was the forerunner of the art known today as Bonsai.
The first time the term potting soil was mentioned was in 1861, in an issue of the American Agriculturist. In the article mentioned, the writer advises that plants that have been set out in pots all summer long should be top dressed with soil, and that the cellar of a home makes a good potting shed, where good potting soil, sand, moss and pots should be stored for later use.