This article was contributed by Shawn Novack, water conservation program manager for the Water Resources Association of San Benito County.
Proper irrigation scheduling is tricky. By far the largest loss of plant materials on new landscape projects is the direct result of improper irrigation scheduling. You may be surprised to learn that the most common irrigation scheduling problem is not too little water or even too much water, it is watering too frequently. Many of the common turfgrass and landscape shrub diseases are made worse by, or even maybe the result of, watering too frequently.
With temperatures warming, more time spent at home due to the coronavirus, we are seeing much more water use in homes throughout the Hollister urban area. The Water Resources Association of San Benito County (WRASBC) wanted to offer some tips to irrigate more efficiently and help reduce water bills.
Since our last big drought, which ended in 2016, many people have transitioned over to drought tolerant landscapes. New homes are also installing drought tolerant plants in their landscapes. Here are a few tips to irrigate drought tolerant plants and lawns. Each has its own challenges when irrigating.
Understand the Water Needs of Your Plants
Plant roots need a combination of both air and water to survive. Some plants, like ivy, can grow in a jar of water. Others will die if the roots are wet for longer than 24 hours. Thus, irrigation scheduling must begin with an examination of the plants to be watered. Most problems related to irrigation scheduling involve irrigation of drought-tolerant plants. Fortunately, almost all plants will perform well under these irrigation scheduling guidelines. As with anything, there are some exceptions.
At this point it may be helpful to understand the needs of drought-tolerant plants. These plants are often native to arid climates where it rains heavily for short periods, followed by long periods with no rain at all. The drought tolerant features of arid region plants allow them to survive and even thrive under these feast or famine water conditions.
Drought tolerant plants may be found growing in all types of soils, from sand to clay. Sandy soils do not hold moisture well and drain quickly. They are the easiest soils to grow drought tolerant plants in when irrigation is available. Clay soils, such as we have here in Hollister, hold water tightly for long periods of time and cause the most problems with over-watering. Watering needs to be much less frequent in clay soils to allow the drying time between irrigations that these plants need.
Never Water if the Soil is Wet
Irrigation scheduling is simply a matter of close observation and dedication. Ideally, the irrigation control clock should be adjusted on a weekly basis to conform with current weather conditions, but even with monthly adjustments plants can be maintained healthy and happy.
The first basic irrigation scheduling rule for drought-tolerant plants is never water if the soil is still wet. The old rule for landscape care was “if it doesn’t look right, water it.” This is often the worst possible thing to do. Plants wilt for any number of reasons other than needing water. Wilting for some perennials happens on hot afternoons no matter how much water they have.
Wilting in drought tolerant plants is often the first sign of too much water (the roots die from too much water, then the plant wilts from lack of water uptake by the roots). Wilting can also be caused by any number of other diseases or even insect damage. Some drought tolerant plants fold their leaves on hot afternoons to conserve water, which can be mistaken for wilting. So never assume a plant needs to be watered because it looks wilted. Check to see if the soil is wet first.
When You do Water, Don’t be Stingy
The other rule for irrigation scheduling is when you do water, don’t be stingy. Saturate the soil throughout the entire planter. The soil should be completely saturated (the technical term is that the soil has reached field capacity) to a uniform depth of at least six inches. The primary feeder roots for most plants will be growing throughout the top six inches of the entire planter, not just under the plant’s foliage. These feeder roots are so small that they are not even noticeable in the soil! The plant’s lower roots are primarily to physically support the plant, although these lower roots can sometimes take up water.
Tips for irrigating lawns
If you’re irrigating using sprinklers, the water will probably start to run off into the gutter, or into a low spot, before the soil is wet to a six inch depth. This is because the sprinklers emit more water than the soil can absorb. Especially with our local clay soils. In technical terms, the precipitation rate of the sprinklers is greater than the infiltration rate of the soil. Fortunately, solving this problem is easy. As soon as the water starts to run-off, just turn off the sprinklers!
The cycle and soak method of applying water to the landscape drastically reduces and, in some cases, eliminates runoff.
This method of applying water to the landscape is made up of multiple cycles for each station with 30 to 60 minutes for the water to soak into the soil between cycles.
- The first cycle will break the surface tension of the soil and saturate the top layer of soil.
- The second cycle infiltrates the soil more efficiently and deeply after the first cycle.
- A third, and sometimes a fourth cycle, is beneficial if a slope is involved or if runoff occurs after the sprinklers run for just a few minutes.
For example: if you have determined you need to run a sprinkler station 12 minutes, schedule your controller run the station two times for six minutes, or three cycles for four minutes. If a slope or runoff is involved, run the station four cycles for three minutes.
Since shelter-in-place orders have been modified, the WRASBC is now available to assist you with landscape irrigation inspections. We can provide recommendations and program your irrigation controller for the summer season. Save water and save money with this free service.
Call (831) 637-4378 to schedule an appointment.
*Some information provided by IrrigationTutorials.com