Tlaloc is the supreme Aztec god of rain, fertility, and water. He blessed civilization with water to sustain crops but also punished them as needed with thunder, hail, and lightning. Our understanding of the natural processes of weather, water, and agriculture may be a bit more scientifically based these days but one thing remains true: Rainwater is uniquely designed to provide just what plants need. It’s slightly acidic and carries nutrients that benefit plant development without the harmful effects of chlorine or other water conditioners.

But how does this play out in the Lab? Just how much better is rainwater than tap water?

Experiment with water sources. Choose 2 six cell packs of starts that are approximately the same size. Water one with treated tap water and one with rain water for a period of 30 days. Depending on the size of your starts, you may have to pot up your starts during the experiment. Take regular measurements for each individual plant and record the growth.

Which plants increased in size by the greatest amount? Which appear healthier? Which have developed more leaves or branches? Is there a difference in root development in just 30 days? Test the soil at the conclusion of the experiment to see if there is a measurable difference in NPK levels.