Get ready, it’s time for plant biology 101. Plants have tiny pores on the undersides of their leaves, through which they suck up carbon dioxide and moisture from the air. At the same time, they absorb water and minerals through their roots. They then use energy from light to convert the carbon dioxide and water into carbohydrates and oxygen. This process is called photosynthesis. The plants use the carbohydrates to refuel, and they release the oxygen back into the atmosphere through their leaves. So plants don’t actually “eat” water—they use it to make their own food. In addition to water, sun, and carbon dioxide, all plants need certain nutrients to survive. The major ones are nitrogen, phosphorus, and potassium, but there are a handful of others as well. They absorb these nutrients from the soil and water, and sometimes they need to be replenished with fertilizer (see the fertilizer section for more).