There are many commercial potting soils available today. Some very good, and others not so good. In order to decide which catagory your potting soil falls into, there are several observations you can make. Good potting soil should be loose and not stick together when squeezed in the hand [1]. The size of soil particles should be in the range of 1/16 to 1/4 inch. This can be determined by passing a sample of the soil through an appropriate-sized sieve [2]. To determine the amount of airspace surrounding the particles, fill a jar with dry soil mix. Using a measuring cup, note how much water you need to add before it starts to overflow. Then drain off the water into a measuring cup. The volume of the water that drains off equals the amount of airspace in the soil. Ideally, you should be able to add two cups of water to one quart of soil, then drain off one cup [3]. In addition, good potting soil should not shrink or swell when watered. Fill a small container with damp, but not wet soil, and observe what happens when you press down on the sample. It should resist compression and not become compacted. The next time you purchase potting soil, look at it again with these observations in mind. Healthy, vigorous plants need quality potting soil in order to reach the expectations we place on them.