You have three choices to make about scheduling:
- What time of day should I water? [If you have an automatic controller, this is usually called Start Time or Cycle Start]
In general, to reduce water loss caused by evaporation, it is best to water during the early morning hours if you are using a spray system. For drip systems, you may choose any time you like. Sometimes wasteful runoff occurs when using watering devices, like sprayheads or bubblers that often apply water faster than the soil can accept it.
To avoid runoff on slopes and heavy clay and silt soils, follow these simple steps:
- Turn on the sprinklers and measure the time it takes before you see water running off or puddling. That time becomes your watering interval.
- Next set several different start times, one for each watering interval, and allow enough time (30-45 minutes) between each interval for the water to soak into the soil before the next start time and watering interval begins. These are called cycle-and-soak intervals.
- Run sufficient cycle-and-soak intervals until the water has sufficiently penetrated down into the soil to provide water to the plant’s roots without it going below the root zone where it is wasted.
- If you have slopes and/or clay or silty soils and if your controller does not have multiple start times for cycle-and-soak options, it is strongly recommended to replace it with a controller with this feature. See Too Much, Too Fast?.
How long should I water? [Run Time or Water Time]
This is the hardest question to figure out. It is the time that it takes to refill the soil reservoir in the rootball of the plants and depends on the type of plant, its root depth, the type of soil and the current weather. It is possible to mathematically calculate this number but someone has already done that for you. Go to Metropolitan’s Web site and use the Watering Calculator to establish a beginning controller program for your garden for your non-native plants.
After living with this program a while you may want to adjust it, but initially the Watering Calculator will put you in the ballpark and assure that you are not over watering. (If you have a native plant garden, over-watering is about the only thing that can kill your plants.) Ordinarily, once you’ve figured out how long to water, that number should only be changed to adjust for root growth.
If you are using a watering device that has a high application rate or the planting area is on a slope or you have clay soil that can’t absorb the water fast enough, it may be advantageous to divide this time up into several shorter watering intervals to avoid run-off. See Too Much, Too Fast? below.
How often should I water? [Day Interval or Skip-A-Day]
(Metropolitan’s Watering Calculator will figure this out for you, too.)
Unless you have a weather-sensitive controller to do the work for you, increasing or decreasing the frequency of watering should be your primary method of seasonal adjustment. The number of days between waterings is the best way to think of this. Unless you have a specific need to avoid watering on certain days of the week, you will find this the easiest way to make seasonal adjustments. Some controllers allow frequency to be scheduled only by days of the week. These settings are referred to as Day Settings, Days of the Week or Days On.