Houseplants Under Lights

Lesson 2: Houseplant Containers & Potting Media

Introduction to Potting Medias

Goal: Student will learn to identify various components commonly found in potting media. They will also learn to select appropriate potting media or to create their own mixes based on the needs of the plant.

Reading Assignment: Find information on the particular houseplant you are potting in Tropical Foliage Plants or Aroids. Learn what its soil requirements are.

The potting media is critical if your plant is to grow and thrive. You must match the media to the plant's needs.

Potting media has several basic purposes. It: 1) holds water for the plant’s use; 2) allows air to reach the roots; 3) supports the plant in the pot; and 4) stores nutrients for the plant. Potting media is made up from various ingredients. Typical ingredients are: compost, peat, topsoil, vermiculite, perlite, bark, and coir. Sand, calcined clay, and even styrofoam are sometimes used. Each of these ingredients has some advantages and disadvantages associated with it.

Potting Media pH

There are two factors that influence the success of anything you plant. These are the pH of your soil and the amount of nutrients available in the potting media. If the pH of the planting media is too high or too low, certain nutrients may not be available to the plants even though they are present in adequate quantities in the media.

What is pH? It is a measure of the amount of hydrogen ions available in the media. This is measured on a scale of 0 to 14 with 6 7 being considered neutral. Below 6 indicates an acidic media and above 7 indicates an alkaline media. Most houseplants and succulents prefer a neutral pH. Therefore, either acidic or alkaline media will need to have their pH adjusted.

What causes a low pH problem? Medias based mostly on peat will have a low pH because peat is naturally acidic. On rare occasions, your water may be too acidic.

What causes a high pH problem? The chief reason for a high pH problem in soilless media is the quality of your water -- whether it is from your own well or provided by the local utility company. Some vicinities are purposely providing alkaline water because it doesn’t clog up pipes as quickly as acidic water can. On the other hand, you may have neutral water, which when combined with a peat-based potting media, results in an acidic potting media. Over time, the pH of your water will change the pH of your media.

How Do You Solve These Problems? Indoor gardeners can test the pH of their media and change it easily. First, fill a container with your potting media. Then soak it with water. Keep some of the water that drains from the media. Using a pH testing kit meant for aquarium keepers, follow the directions on the bottle and check the pH of the water you drained off the test pot. If it tests in the acidic range, buy some of the liquid aquarium keepers use to raise the pH; alternatively, if the test result is alkaline, buy the liquid fish keepers use to lower pH. Follow the directions on the bottle of either product. Some people use vinegar in a gallon of water to lower the pH of water. If you choose this route, you’ll still have to test your water. Then you have to experiment to see just how much vinegar you need to add to bring the water into the neutral pH range.

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