Well, summer is here and now is the time when we at the garden centers get questions about how to water the landscape. Is drip irrigation better than bubbler irrigation? How long do I water, or how many gallons do I need to give our plants each week? I have always said I donít care how you water your plants, whether you use a teaspoon or a fire hose to apply the water, itís the soil moisture depth and the frequency that is important.
With that in mind, letís talk about the types of irrigation systems we use. In the early days of irrigation in the valley, bubbler systems were used for shrubs, trees, and groundcovers. The advantage to this type of system is they deliver a large amount of water in a short period of time. This method is good for flushing through the salts in the soil, but they also have a tendency to deliver too much water and cause runoff. Another disadvantage is its cost. These systems used all PVC pipe or hard pipe as it is called. Drip systems use a poly pipe which is much less expensive and much easier to install. Drip systems may not cause runoff but they can cause salt build up in the soil if run for short periods of time, and on a frequent basis. The salt can also accumulate around the opening of the emitter and cause them to clog. These systems require constant maintenance. So as you can see, no system is without problems.
Now that we have discussed systems, letís talk about the watering itself. As we continue remember that we are referring to established plants, (plants that have been in the ground at least one year). Newly planted plants need more frequent watering through the first summer to insure that they develop the proper root system.
Water should be delivered very slowly over a long period of time. The soils in most areas around the valley are heavy clay. Water is slow to be absorbed into the ground but is also slow to be drawn from the soil, so once in the ground it will remain for a longer period of time than you think. Trees should be watered on 7 to 14 day interval, depending on the species, and achieving soil moisture depth of 3 to 5 feet. Shrubs should the watered on a 5 to 10 day cycle with a soil moisture depth 18 to 36 inch depth. Ground covers and annual flowers need a more frequent supply of water, but much shallower, 4 to 8 inches. Be careful not to over water.
If you would like, come by the nursery, we have a sheet of instructions for watering both new plantings and established plantings and would be happy to give you a copy to help you establish your watering schedule to insure the health and vigor of your landscape plantings.
By: Mark Scaife