I was visiting my dad this past week. Since he is now 94, he asked me to check the irrigation clock at his south Florida home to see if the cycle days and times would accommodate the summer temperatures. Over the years, we have had many discussions about this topic as his home locations have ranged from climatic hardiness Zone 5 to Zone 10, from clay soils to sandy. How much water a plant requires depends on the plant, the soil texture (the proportion of sand, silt and clay-sized particles that make up the mineral fraction of the soil), soil structure (the arrangement of the solid parts of the soil and the pore spaces located between them), the amount of rainfall, the temperature extremes and the slope of the land. However, there does exist common methodology for irrigation practices.
• Water at the right time. It is best to water early in the morning before 10 a.m. If you have irrigation and a time clock, it might mean that the first zone starts at 3 a.m.!
• Lawns require 1 to 1.5 inches of water per week; allow for 1/3” of water every two days. If you can see footprints when you walk across the lawn or if the blades of grass are folded, your lawn is thirsty. If you can see your footprints when you walk through the grass or if the blades of grass are folded, these are indications that your grass needs more water.
• Water deeply. Shallow watering encourages shallow roots. Deep roots increase drought hardiness.
• Warmer climates, in which soil doesn’t freeze and plant roots grow year-round, require watering year-round.
• Water rates are critical. How much water does your system put out? Place empty cans around the yard. Turn on your system and see how long it takes to fill the cans with an inch of water in each zone. If it takes an hour, then you might want to have the system turned on three times a week for 20 minutes at a time.
• Water absorption is important. Note how quickly water is absorbed into the soil. If water runs off down the driveway or sidewalk, or pools in the lawn, the soil isn’t absorbing the water well. This results in water loss, as well as possible loss of soil and nutrients. Break up the watering times to allow the water to soak deeply into the lawn.
• Separate irrigation zones with spray heads from those with rotor heads. The two don’t mix well. Spray heads are fixed heads that pop up and spray one area continuously. They have an optimal operating pressure of 30 psi and a precipitation rate (how fast water is being applied to a given area, in inches per hour) of 1.5 to 2 inches. Spray heads are used in smaller areas. Rotor heads rotate from side to side and have a large stream of water that comes out which can cover a radius of 15-50 feet. The optimum pressure is 45-50psi and the precipitation rate is between 0.5-1 inch per hour. Rotor heads are the better choice for larger areas of turf because of the low precipitation rate which allows for even coverage over a longer period of time.
For my dad’s landscape, which no longer has turf (a choice made last year to move toward use of ornamental stone, statuary and accent plants), the spray irrigation system is watering the remaining flower beds around the perimeter, and it is set to water three times a week for 15 minutes each. The beds were already in place and the soil never amended with organic matter. Beds were covered with landscape fabric and stone, so it took some experimentation to see the amount of water necessary to keep the mixture of plants including plumbago, asparagus fern, Knockout® roses, hibiscus and fire bush well-watered.
If you don’t have lawn but lots of ornamental pots like I do, some of the above points can also be applied. I water slowly, thoroughly and in the early morning. I find that good quality potting soil, larger containers, and container placement out of direct afternoon sun (if possible) help to reduce watering frequency. However, as the summer progresses, some planters will require daily watering. This leaches out soil nutrients, so I add supplemental liquid fertilizer at low rates once a week if plants show signs of deficiency. All my containers have good drainage holes. I don’t add gravel to increase drainage. It does NOT. Science has proven that the longer the continuous soil column, the better the drainage. When watering, I try to water at a slow rate to ensure that the soil actually is taking up the water and water is not simply running down the inside of the pot and out of the holes. I do water everything once and then return to water everything a second time. Water will slowly seep out of the bottom of the container, letting me know that the entire soil column has been watered.
I’ve made sure that containers with more than one species of plant are comprised of plants with similar watering needs. I’ve added more succulents which require less watering and moved away from plant species that wilt in the afternoon heat regardless of watering because their leaves are losing moisture too quickly for the roots to replace it. Gardening is about experimentation and experience. As your knowledge grows, so does your success!