This is something that’s not easy to agree on. In California, we have WUCOLS (Water Use Classification of Landscape Species) to determine the plant factor (crop coefficient); however there is still exposure, climate zone, soils, slope, soil interface between clay, loam (sand nursery soil) and the native site soil.
I have found that a majority of our landscape plants can survive with very little supplemental water once established. We have all seen areas where plants survive with very little supplemental water.
Plants need to be grouped in hydrozones so plants that need water, get water.
I think we tend to water because it makes us feel good – but it’s becoming a very expensive habit – not because the plants need water.
I live in Orange, California and every Fall I turn off my irrigation system after the first significant rain and keep it off as long as possible. My lawn tends to gets stressed in the Spring long before my shrubs ever show signs of stress. I start by hand watering the stressed areas (difference in soils, sun shade, tree roots taking various amounts of water out of the soil) and I restrain from turning on my Irrigation system as long as possible.
Recently I attended an Orchid Society meeting last month and listened to a presentation on Australian Dendrobium “Rock Orchids.” They grow on rocks and in trees the east coast of Australia. During our Winter (their Summer) they go for several months with out water.
I happen to have a Dendrobium Orchid that I bought when it was blooming and it hasn’t bloomed since. And that was over 10 years ago! I would always water it in the Winter, because plants need water but this year I am going to move it out of the rain. I am going to make sure it does not get any water this Winter. So wish me luck on blooms this Spring!
How much water do your plants really need?
Maybe a lot less then you think!