Want fresh lettuce without the fuss? Skip the soil and learn how to grow it hydroponically on your countertop or windowsill.

The process chemically converts carbon dioxide (CO2) and water into food (sugars) and oxygen. The chemical reaction often relies on a pigment called chlorophyll, which gives plants their green color.

Q. Can tomato plants absorb water through their leaves on humid days? Also on cool and hot days, how often do you need to water with our heavy clay soil? – C.W., Crown Point, Ind. A. While plants can ...