There are several reasons for measuring your plants, such as finding the best location for them or determining the best medium, fertilizer and soil. Measuring plant growth is a very simple procedure that can be done quickly with a minimum of effort and tools.It takes just a little time and patience, especially if you are starting your plants from seeds.ips. 1  When measuring from the bottom to the tip of your plant, do not put the ruler directly on the dirt because the dirt surface can become higher or lower depending on the amount of moisture.