What Do "Infrequent" and "Moderate" Mean?

Q. I’ve checked the internet and have some information from our state, but I still can’t compare the terms “infrequent" and "moderate”. Does “infrequent” mean once every two weeks?  Once a month? And what does “moderate” mean? 1 gallon per watering?

Root depth of plants has to do with their size, genetics and the kind of soil. The deepest roots are with large trees, from an arid climate and growing in a sandy soil.

A. I agree those terms are misleading. I think those terms are used by people who don’t understand the differences themselves or they would explain them. "Moderate" amounts of water refers to the amount of water a plant is given. "Infrequent" referst to the frequency of water or how often water is given. These are the two major concepts related to irrigation and are used to schedule any irrigation controller. It sounds like a topic for my audio podcast, Desert Horticulture.

Big Plants Need More Water

            Two concepts should be understood. Bigger plants have deeper roots. Deeper roots are encouraged with "infrequent" watering. This is about how often to give water. Plant roots extract water from the soil deeper and deeper as the soil at the surface gets drier and drier. The surface roots are the first to “suck up” water after an irrigation. The roots take water from the soil deeper and deeper as the soil gets progressively drier toward it’s surface. As we water plants “infrequently”, the roots extract water and grow into deeper and deeper layers of soil. Deep rooting of plants is the main reason good gardeners say, “Water plants deeply but infrequently.”

Get Away from Daily "Small Sips" of Water

            The major reason we do not give plants “tiny sips of water” daily is because this type of watering practice encourages plants to grow their roots more shallow. There is a second reason; tolerance to heat. Plants with deeper roots have a better chance of withstanding the heat of summer.

            “Moderate” amounts of water relates to the amount given to the plant. It usually means enough water to “wet the roots growing in the soil” and little or no more. We learned that the depth of plant roots depends on the size of the plant; bigger plants frequently have deeper roots than smaller plants. The depth of plant roots also varies with the genetics of the plant and the type of soil.

Water "Infrequently"

            The deepest roots are with those plants that are large, have the genetic potential to grow deep roots and grow on sandy soils. The shallowest roots are found on small plants that don’t have the genetic potential for deep roots and grow in a heavy clay soil.