I’m often asked, “How much should I water my landscape?”
Sounds like a simple question, but there is no simple answer. There are multiple variables that must be considered before a plan can be developed for the different parts of a home landscape, including the types and ages of plants, soil texture and condition, and details of the site, such as slope and exposure.
Soil texture measures the percent of sand, silt and clay in a soil. The texture of garden soil plays a huge role in irrigation management and is often the area where homeowners know the least about their garden.
The higher the percentage of small clay particles, the more water that soil will hold and the less often you will have to irrigate. In my sandy-clay soil, the surface dries out quickly while the root zone stays damp for days longer. Clay soils are also easy to compact, reducing the infiltration of both water and the oxygen needed for healthy roots.
There is an inexpensive home test for soil texture that requires only dry soil, some dishwasher soap, a glass jar and water. You can in Colorado Master Gardener GardenNotes No. 214, Estimating Soil Texture, at www.cmg.colostate.edu/gardennotes/214.pdf
You should conduct separate tests for your lawn, vegetables gardens and flower beds, especially if you have added amendments over the years.
Roots mine the soil for water and nutrients, so rooting space plays a role in irrigation management. Roots grow out, not down, so the size of your yard, soil conditions and competition between plants will influence how often you need to water. The smaller the area for roots, from small yard to containers, the more critical your irrigation management becomes.
Water needs differ by plant species, stage of life and local climate conditions. Colorado State University Extension fact sheets, available at extension offices or online, list plants as needing low, medium or high irrigation, based on the needs of mature plants.
When plants with different needs are planted together, we often water for the species with the highest water needs, creating unhealthy conditions for those plants that prefer drier conditions.
Plants of the same species may need different irrigation schedules in the same landscape. A rosebush on the south side of the house, in full sun and reflected heat, will need more water than a rosebush on the east side of the house, where it gets afternoon shade. Needs change as the weather heats up, so a bluegrass lawn that needs water once a week in April may require three times a week in July.
So, I have no quick answer to the “How much should I water?” question. Don’t get discouraged when my answer is, “It depends.” A recommendation will be based on the needs of plants in your particular soil, watered deeply but infrequently to allow time for drainage. The goal must be to keep the roots healthy so that the above-ground plant structures can thrive.
