water
In this module, you'll learn about how water is used in plants, more about how it flows through soil and over landscapes, about the different types of irrigation, and how to conserve this precious resource.
"Water is the driving force of all nature."
- Leonardo di Vinci
- Leonardo di Vinci
introduction
Water is a vital, life-giving force in the garden that should not be overlooked when planning and caring for your space. Learning how water flows across your property, how it is used by plants, and how it can be conserved and saved for periods of drought are all pieces of knowledge that will assist in creating a water-wise garden.
How Plants Use Water
.Water typically constitutes 85% to 90% of the weight of a plant, and supports essential life processes that occur within plant cells. It plays an important role in transporting dissolved minerals from the soil and sugars from the leaves to all cells in the plant, maintains cell turgor, or rigidity, and indirectly regulates growth. The importance of water to plant life can really not be understated, no matter how drought-tolerant the plant is. Water enters the soil through precipitation (rain, snow, and the like) or irrigation, and then enters plants alongside nutrients drawn from the soil. After the plant has used what water it needs, the rest is released into the atmosphere in the form of water vapor. This process is called transpiration.
|
A second way that garden water is lost to the atmosphere is by evaporation. Evaporation is the process by which liquid water turns into gaseous water (water vapor), and is then taken up into the atmosphere. Evaporation happens when heat energy breaks apart the molecules that hold water together. Most of the water in our atmosphere comes from water that has evaporated from bodies of water, such as oceans, lakes, and rivers. The rest of the moisture in the air comes from plant transpiration (and a little bit is due to sublimation - water transforming from its solid state (ice) directly into a gaseous state. In the garden, evaporation occurs when water in the soil heats to a temperature at which it is then pulled from the soil and lost to the atmosphere. The total amount of water lost within a garden is called evapotranspiration, or ET (evaporation and transpiration combined).
Quick Question: How does water travel from the roots to the top of a plant?
It seems remarkable that water can travel against gravity up through the interior of a plant, sometimes 50 to 100 feet or more. Water molecules have strong bonds within themselves and with other neighboring water molecules. This produces a great tensile strength. Water molecules form a chain up the interior of a plant through the system of channels of xylem that exist within stems and leaves. As the molecules move towards the exits (stoma) of leaves, they pull their neighboring water molecule with them, and so on and so forth along the water chain down to the roots. As water is lost through evaporation through stomata, more water is pulled from the other end of the water molecule chain into the plant.
It seems remarkable that water can travel against gravity up through the interior of a plant, sometimes 50 to 100 feet or more. Water molecules have strong bonds within themselves and with other neighboring water molecules. This produces a great tensile strength. Water molecules form a chain up the interior of a plant through the system of channels of xylem that exist within stems and leaves. As the molecules move towards the exits (stoma) of leaves, they pull their neighboring water molecule with them, and so on and so forth along the water chain down to the roots. As water is lost through evaporation through stomata, more water is pulled from the other end of the water molecule chain into the plant.
Evapotranspiration (ET) rates vary among plant species, and is driven by the sun and other environmental factors such as heat, humidity, and wind speed. It is expressed in units of depth (either inches or millimeters) or volume (either gallons or liters) per length of time (days, weeks, months, or years). The rate of evapotranspiration when graphed creates a bell curve through the year, with higher rates in the middle of summer and lower rates in the middle of winter. The chart shown here illustrates this trend, showing monthly average ET for various zones in California.
|
ET rates also vary depending on soil types, with sandy soil holding on to 1/4 to 1/6 of the amount that clay soil can hold. A plant in clay soil requires just as much water as the same plant growing in sandy soil, but because the soils hold water differently, they will need to be watered differently. Because there are so many factors at play in estimating ET rates, location-specific data has been collected and published for quick reference. To use this data, begin by finding your ET zone on the map of California. Then, find that zone on the ET average rate chart.
|
the way of water
The initial entry of water into soil is called infiltration. The infiltration rate represents how quickly water enters into soil, expressed in inches or centimeters per hour. It is determined by soil qualities like structure and type, the type of cover on the surface of the soil, the slope of the land itself, the current water saturation of the soil, and water quality. How readily water moves downward through the soil profile is referred to as percolation or permeability. For example, the same volume of water will travel downward through soil farther in sandy soil than it would in clay or loam soil. Good infiltration and permeability are very important factors in the garden because they ensure that required water reaches the root zone of plants, that runoff and erosion are mitigated, and that air can move efficiently into soil pore space.
When the application rate of an irrigation system is greater than the infiltration rate of the garden soil (or if the soil is already fully saturated when the irrigation is applied), runoff occurs. Runoff is an issue for a few reasons. It is wasted water that will not be used by plants, and it can cause soil erosion. Additional water can also be lost underneath the root zone, where it is not accessible by plants; a process called deep percolation. If there is no slope to the garden, water can also form pools of standing water on a property, and if this occurs where plants are situated, they can drown.
The drainage situation on a property can be measured using a simple test. First, dig a hole 12-18 inches deep and fill the hole with water. If your soil is dry to start with, allow the water to drain out of the hole completely, and then fill it again. Monitor how long the water takes to drain out of the hole. If all water is gone from the hole within a few hours, drainage in the garden is considered adequate for most plants. If the hole takes 24 hours or more to drain, drainage is slow and your plants may be suffering as a result. In this latter situation, soil will need amending with organic matter in order to create a welcoming environment for plant roots. Slow drainage in garden soil can be caused by the soil being clay-rich, restrictive horizons or claypans, dense or compacted layers, abrupt changes in soil texture in a short distance, or a high groundwater table. For information on how to amend soil in these situations, see the Soil module.
CONTROLLING WATER ON YOUR PROPERTY - dealing with extra water
When the application rate of an irrigation system is greater than the infiltration rate of the garden soil (or if the soil is already fully saturated when the irrigation is applied), runoff occurs. Runoff is an issue for a few reasons. It is wasted water that will not be used by plants, and it can cause soil erosion. Additional water can also be lost underneath the root zone, where it is not accessible by plants; a process called deep percolation. If there is no slope to the garden, water can also form pools of standing water on a property, and if this occurs where plants are situated, they can drown.
The drainage situation on a property can be measured using a simple test. First, dig a hole 12-18 inches deep and fill the hole with water. If your soil is dry to start with, allow the water to drain out of the hole completely, and then fill it again. Monitor how long the water takes to drain out of the hole. If all water is gone from the hole within a few hours, drainage in the garden is considered adequate for most plants. If the hole takes 24 hours or more to drain, drainage is slow and your plants may be suffering as a result. In this latter situation, soil will need amending with organic matter in order to create a welcoming environment for plant roots. Slow drainage in garden soil can be caused by the soil being clay-rich, restrictive horizons or claypans, dense or compacted layers, abrupt changes in soil texture in a short distance, or a high groundwater table. For information on how to amend soil in these situations, see the Soil module.
CONTROLLING WATER ON YOUR PROPERTY - dealing with extra water
IRrigation systems
Irrigation (also referred to as watering) refers to the artificial application of water to soil through a variety of systems. There are many ways to apply water to a landscape, including surface irrigation (or gravity irrigation), sprinkler irrigation, micro irrigation, drip irrigation, and subirrigation. Irrigation has been a vital aspect of agriculture and gardening for the past 5,000 years, and has been developed by many cultures around the world.
The History of Irrigation
The earliest archaeological evidence of irrigation in farming dates back to 6,000 BC in the Jordan Valley. Around this time, agriculturalists in Egypt were also creating formal irrigation systems to provide additional water to crops to support a growing population. The earliest pictoral representation of irrigation is found in Egypt dating back to 3,100 B.C. From these areas, the use of irrigation systems spread through Persia, the Middle East, and along the Mediterranean Sea. Irrigation systems also appeared around this time in Pakistan, India, China, and in the Inca, Maya and Aztec civilizations. Irrigation was first introduced into the United States in what is now Arizona, in the 13th and 14th centuries. Some of these irrigation systems stood the test of time, but sadly others caused irreparable damage to the landscape and surrounding ecology. In areas where irrigation systems proved successful, additional water-centric engineering projects were created, including dams, canals, dikes, and water storage facilities. During the 20th century, the amount of irrigated land doubled; at this time, about 18 percent of the world's land area is formally irrigated, and these areas feed approximately 80 percent of the world's population.
Modern Irrigation Systems
There are many techniques that have been developed over the history of human civilization to irrigate landscapes. In this section, we will describe how water is used in residential landscapes and for kitchen gardens. Disregarding which irrigation system is used, there are a few overarching rules to making sure it is functioning correctly and in the right capacity. Correctly installing and maintaining your watering system is critical for the long-term success of the surrounding ecosystem, the health and development of your plantings, and for conserving water. The following tips will ensure that an irrigation system performs efficiently.
Irrigation lines that feed sprinkler heads or drip emitters should be placed perpendicular to slopes rather than parallel to them. Spray heads should also be placed perpendicular to slopes. This will ensure that water does not simply roll down the hill on the surface of the soil instead of being absorbed into the root zone of irrigated plants. |
Automated Sprinkler Systems and Weather-Sensing Controllers
These state-of-the-art watering systems are widely used by home gardeners across California. These automatic systems provide multiple irrigation programs and cycles, can adjust in response to weather and climate conditions, and some can even interface to your computer or smartphone. They can be used with many different water delivery methods, including drip, sprinklers, and hoses. Specialized weather-sensing controllers automatically adjust waterings depending on weather conditions with the goal of conserving water. These systems usually require some tweaking by experienced horticulturalists to work at peak efficiency.
These state-of-the-art watering systems are widely used by home gardeners across California. These automatic systems provide multiple irrigation programs and cycles, can adjust in response to weather and climate conditions, and some can even interface to your computer or smartphone. They can be used with many different water delivery methods, including drip, sprinklers, and hoses. Specialized weather-sensing controllers automatically adjust waterings depending on weather conditions with the goal of conserving water. These systems usually require some tweaking by experienced horticulturalists to work at peak efficiency.
Hose-End Sprinklers
Using hose-end sprinklers is a common practice among many Californians who use them to water lawn areas and other plantings. To cover large swaths of land, multiple sprinklers can be used or a single sprinkler can be moved periodically during the watering cycle. Using this type of irrigation requires some ongoing upkeep and monitoring, including:
- Checking for leaks between the faucet and hose. Sometimes, new rubber washers may be needed to replace degraded ones. These washers are inexpensive and easy to install.
- Placing the sprinkler head in a central location surrounded by the plants intended to be watered. Avoid placing these sprinklers near sidewalks, driveways, and structures unless their flow can be directed so that water is not wasted on these hard surfaces.
- Using sprinklers responsibly so that their spray does not come into contact with tree trunks, and so that the output is directed towards their intended targets.
- Using a separate type of irrigation for trees and established shrubs that allows for a slower, deeper soak.
Furrow Irrigation
This technique is best used for fruit and vegetable plantings, and does well in raised beds. This technique is valued because it does not wet the foliage of plants, decreasing the risk of fungal diseases.
This technique is best used for fruit and vegetable plantings, and does well in raised beds. This technique is valued because it does not wet the foliage of plants, decreasing the risk of fungal diseases.
Drip Irrigation
This popular type of irrigation rests on the fact that it is best to frequently and slowly irrigate landscapes. Emitters in this system are spaced along delivery lines 1/2 inch in diameter. Basic drip systems have three parts: a flow control, pressure regulator and filter; a system of flexible plastic hose, and emitters. Drip irrigation waters a limited area of soil, a portion of the plant's root systems, reduces water waste in the area between plants and minimizes water evaporation, and prevents germination of weed seeds in between plants. Drip irrigation systems work well for many areas of the garden and for a wide variety of plants, including vegetables, ornamental and fruit trees, shrubs, vines, and containers. Soaker hoses are a related form of irrigation, but they do not provide as uniform waterings as does a true drip system.
Drip irrigation systems have many benefits. Water gets more accurately and efficiently placed in the root zone. Runoff is minimized due to the slow speed at which water is dispersed. The foliage of watered plants remains dry, reducing disease. The space between plantings also remains dry, giving gardeners more space to work in the garden. There are some issues with this type of system, including the initial cost required in labor and materials, as well as the ongoing maintenance required to keep the system in working order. Otherwise, drip irrigation is ideal for most garden water needs. For more information on setting up a drip irrigation system, visit the page linked here:
This popular type of irrigation rests on the fact that it is best to frequently and slowly irrigate landscapes. Emitters in this system are spaced along delivery lines 1/2 inch in diameter. Basic drip systems have three parts: a flow control, pressure regulator and filter; a system of flexible plastic hose, and emitters. Drip irrigation waters a limited area of soil, a portion of the plant's root systems, reduces water waste in the area between plants and minimizes water evaporation, and prevents germination of weed seeds in between plants. Drip irrigation systems work well for many areas of the garden and for a wide variety of plants, including vegetables, ornamental and fruit trees, shrubs, vines, and containers. Soaker hoses are a related form of irrigation, but they do not provide as uniform waterings as does a true drip system.
Drip irrigation systems have many benefits. Water gets more accurately and efficiently placed in the root zone. Runoff is minimized due to the slow speed at which water is dispersed. The foliage of watered plants remains dry, reducing disease. The space between plantings also remains dry, giving gardeners more space to work in the garden. There are some issues with this type of system, including the initial cost required in labor and materials, as well as the ongoing maintenance required to keep the system in working order. Otherwise, drip irrigation is ideal for most garden water needs. For more information on setting up a drip irrigation system, visit the page linked here:
Basin Irrigation
For tree or shrub plantings, basin irrigation is recommended. This method requires building up a doughnut-shaped basin around the base of the plant with a berm under the drip irrigation line and a second berm closer in to the trunk to prevent water from touching the trunk itself.
For tree or shrub plantings, basin irrigation is recommended. This method requires building up a doughnut-shaped basin around the base of the plant with a berm under the drip irrigation line and a second berm closer in to the trunk to prevent water from touching the trunk itself.
irrigation tips and best practices
There are many ways in which irrigation systems can be managed to best maintain healthy landscapes and gardens and save as much water as possible.
Create Hydrozones
Plants with similar water needs should be grouped together in irrigation zones. An irrigation zone refers to an area watered by the same valve and controller station. Grouping plants in this way allows the correct amount of water to be applied to plants at the correct time, and leads to healthier planting beds overall. Planting beds with plants that have differing water needs will need to be manually watered to ensure that each plant is getting adequate water down to its root zone. |
Apply the Correct Amount of Water
In general, overwatering plants is much more common than underwatering plants. Research shows that many plants are overirrigated by 20-40 percent or more. Even on hot summer days, many plants are overwatered. This is partially due to the fact that California soils are clay-heavy, and hold more water and dry out more slowly, making them more susceptible to being overwatered. To judge whether a garden is being overwatered, a simple test can be done. The main piece of information needed to determine how much water a landscape needs |
If plants are watered manually with a hose, turn it on at the force that is commonly used for watering, and time how long it takes in minutes to fill a one gallon container. This will be the rate of water application for this method. If a drip system is used, they are usually designed to deliver between 1 and 3 gallons of water per hour. A gallon of water adds 1.6 inches of water over a square foot of dry land and wets the area to a depth of 1.5 inches (though this integer depends on soil texture and existing soil water content when the water is added). Another way to look at it is that 0.62 gallons of water applies an inch of water to square foot of garden soil. A handy equation to use to estimate water application rates is:
inches of water =
|
gallons
|
|
(sq. ft. of planting area x 0.62)
|
The right amount of water needed for your landscape and garden plantings will depend on the ET rates in your area (which depends on your specific microclimate). There are eleven established zones in California that have distinct average ET rates depending on the month of the year. This data is contained in the table found in the 'How Plants Use Water' section above.
Water Plants Deeply and Infrequently
The soil should be wet to just beyond the root zone of established plantings, and the soil should be allowed to dry out a bit in between irrigations. By engaging in this practice, root rot diseases are discouraged, and a water reservoir is established, providing adequate water for all plants in the area when they need it. In areas where there is little rainfall, such as deserts, extra water must be applied occasionally to leach salts out of the root zone so that it does not harm plant roots. If using a drip irrigation system, schedule with short intervals between irrigations in order to keep soil adequately wet. Knowing the root depth of your plants is a key piece of information needed when determining how deep you need water to percolate into the soil. In general, the following plant categories will have different rooting depths:
The soil should be wet to just beyond the root zone of established plantings, and the soil should be allowed to dry out a bit in between irrigations. By engaging in this practice, root rot diseases are discouraged, and a water reservoir is established, providing adequate water for all plants in the area when they need it. In areas where there is little rainfall, such as deserts, extra water must be applied occasionally to leach salts out of the root zone so that it does not harm plant roots. If using a drip irrigation system, schedule with short intervals between irrigations in order to keep soil adequately wet. Knowing the root depth of your plants is a key piece of information needed when determining how deep you need water to percolate into the soil. In general, the following plant categories will have different rooting depths:
Although plants vary in their rooting depths by species and variety, they can be classified into these three groups generally. There are many limiting factors that can affect a plant's genetic rooting potential, so it is best to sample soil around a given plant to more accurately estimate the exact depth of its root system.
Water Early in the Morning
In the early morning, conditions are perfect for applying water to a landscape. There is generally less wind and conditions are cooler, reducing evaporative water loss and disruption of sprinkler pattern uniformity. Because watering early in the morning usually means watering when no one is around, it is important to check irrigation systems regularly for broken or inoperative components and leaks that may otherwise go undetected. The exception to this early watering guideline is with drip systems, whose water is released in such a slow, direct manner to the soil surface. These systems can be efficiently operated at any time of the day, without much reason to worry about water loss through evaporation. |
Avoid Deep Percolation and Runoff
Overwatering can lead to both deep percolation and runoff, both of which are wastes of garden irrigation water. Deep percolation refers to significant water movement below the root zone of plants. This water is not available for uptake, and is therefore wasted. Applying water for shorter periods of time can substantially reduce this issue. Due to the structure of some soils, there is more of a problem with runoff than with deep percolation. Runoff occurs when soil infiltration is poor; the water simply hits the soil surface and 'runs off'. Applying water at lower rates, for example using a drip system instead of hose watering, can greatly improve runoff issues in the garden. Cycling water can also reduce runoff. This process involves splitting waterings into multiple irrigations rather than one, spaced several minutes to an hour apart while the soil is still moist but able to take in more water.
If issues with runoff are present in a garden, a great way to establish a healthy watering schedule is to apply water every hour for 5-10 minutes or until runoff begins. Repeat this cycle as many times as it takes to wet the soil to the depth of the surrounding plants' root systems. Although this will take some time investment to begin with, after an ideal irrigation schedule is built, it can be followed with ease and tweaked for seasonal changes. Runoff can also be avoided by not using high-output fixed-head sprinklers, which usually apply water more quickly than it can be absorbed into the soil, especially in sloped areas of the garden. Choosing rotating spray or stream heads that apply water very slowly. Although these types of irrigation need to be run for much longer to apply the same amount of water, the water applied is actually able to be used by plants. In sloped areas, drip irrigation is highly recommended, as well as low-volume micro- and mini-sprinklers.
Overwatering can lead to both deep percolation and runoff, both of which are wastes of garden irrigation water. Deep percolation refers to significant water movement below the root zone of plants. This water is not available for uptake, and is therefore wasted. Applying water for shorter periods of time can substantially reduce this issue. Due to the structure of some soils, there is more of a problem with runoff than with deep percolation. Runoff occurs when soil infiltration is poor; the water simply hits the soil surface and 'runs off'. Applying water at lower rates, for example using a drip system instead of hose watering, can greatly improve runoff issues in the garden. Cycling water can also reduce runoff. This process involves splitting waterings into multiple irrigations rather than one, spaced several minutes to an hour apart while the soil is still moist but able to take in more water.
If issues with runoff are present in a garden, a great way to establish a healthy watering schedule is to apply water every hour for 5-10 minutes or until runoff begins. Repeat this cycle as many times as it takes to wet the soil to the depth of the surrounding plants' root systems. Although this will take some time investment to begin with, after an ideal irrigation schedule is built, it can be followed with ease and tweaked for seasonal changes. Runoff can also be avoided by not using high-output fixed-head sprinklers, which usually apply water more quickly than it can be absorbed into the soil, especially in sloped areas of the garden. Choosing rotating spray or stream heads that apply water very slowly. Although these types of irrigation need to be run for much longer to apply the same amount of water, the water applied is actually able to be used by plants. In sloped areas, drip irrigation is highly recommended, as well as low-volume micro- and mini-sprinklers.
Apply Water Uniformly
Even applications of water over a planted area reduces water loss and improves the health of plants. This tip is especially useful to consider when applying irrigation to a lawn area. When sprinkler systems are not balanced properly, some areas of a lawn will receive much more water than others, as illustrated in the photograph shown. Brown, drought-stressed grass areas will develop, inviting weeds to take hold and creating a less-than pleasing look. Many homeowners will simply run their sprinkler systems for longer periods of time in the hope that the water will simply just 'spread out' and cover the entire lawn, but instead can cause overwatering problems as well as drought problems across the entire lawn. |
A homeowner's sprinkler system that is applying water half as evenly as their neighbors' will require about twice as much water to ensure that all areas of the lawn are properly saturated. Over the course of a summer season, this can lead to both higher water bills as well as a high amount of wasted water due to runoff. Regularly conducting can tests can ensure that uniformity problems are detected, and possible hardware issues can be corrected.
Maintain and Adjust Irrigation Controllers and Systems
When seasons change, the ET rates and water needs of plants change, as well. Lower amounts of water are required over the late fall, winter months, and early springtime and more is required in summertime. Adjusting irrigation according to these seasonal changes can decrease water use over the year by up to 50%, and also can enhance plant health. Areas with established deciduous trees and shrubs need hardly any water over the winter months, as long as rainfall is near normal. Many landscape trees, shrubs, ground covers, and lawns are overwatered during fall and winter because automatic irrigation systems are not adjusted. |
Checking irrigation systems regularly for physical and operational problems is key to preventing water waste in the garden. A simple way to check an irrigation system is to turn it on and walk around the yard, taking note of anything that looks out of the ordinary. Correcting issues in irrigation systems can reduce water waste by between 20% and 50% and can also improve plant health.
Apply Mulch
Planting beds benefit greatly from a layer of mulch applied 2-4 inches deep on the surface of the soil. This is one of the most beneficial things a homeowner can do for their garden; the use of mulch can help insulate soil from drastic changes in temperature, suppress weed growth, provide slowly-leaching nutrients (if an organic mulch is used), and, most importantly for this discussion, reduce water evaporation from the soil. Intervals between irrigations can be lengthened with the use of mulch; yards using mulch will require less frequent waterings than those with bare soil. When applying mulch, it should be kept away from plant trunks and stems by several inches, and extend outward toward the drip line. Soil under the mulch layer should be checked periodically to ensure that water is penetrating the soil through the mulch. Drip lines should be installed underneath the mulch layer.
Planting beds benefit greatly from a layer of mulch applied 2-4 inches deep on the surface of the soil. This is one of the most beneficial things a homeowner can do for their garden; the use of mulch can help insulate soil from drastic changes in temperature, suppress weed growth, provide slowly-leaching nutrients (if an organic mulch is used), and, most importantly for this discussion, reduce water evaporation from the soil. Intervals between irrigations can be lengthened with the use of mulch; yards using mulch will require less frequent waterings than those with bare soil. When applying mulch, it should be kept away from plant trunks and stems by several inches, and extend outward toward the drip line. Soil under the mulch layer should be checked periodically to ensure that water is penetrating the soil through the mulch. Drip lines should be installed underneath the mulch layer.
Amend High Sand or Clay-Content Soil
Soil high in clay content tends to repel water, leading to issues with runoff and poor percolation. Amending this type of soil with organic matter will improve structure, and therefore allow more water to reach the root zone. Sandy soils have issues with deep percolation, where water passes right through the root zone and is not available to plants. Sandy soil amended with organic matter will hold more water and require less frequent irrigation.
Soil high in clay content tends to repel water, leading to issues with runoff and poor percolation. Amending this type of soil with organic matter will improve structure, and therefore allow more water to reach the root zone. Sandy soils have issues with deep percolation, where water passes right through the root zone and is not available to plants. Sandy soil amended with organic matter will hold more water and require less frequent irrigation.
situation-specific Water management strategies
Because there are so many variables that affect how water flows across a property and is used by plants in the garden, it is a good idea to create different irrigation practices for each distinct area. The following tips and considerations will assist in planning out or tweaking an already existing irrigation plan depending on the types of plantings present in the garden.
Annuals and Perennials
Newly installed beds of annual and perennial plants require frequent and uniform supplies of water while their roots are getting established in the soil. It may be necessary to apply water one or more times during warm or windy weather. Once established, irrigations can be reduced. For mature beds, water can be applied every two to three days at about 75% to 100% of ET. During cool weather, irrigation can be applied 1-2 times per week. Enough water to rewet the root system should be applied at each planting.
Newly installed beds of annual and perennial plants require frequent and uniform supplies of water while their roots are getting established in the soil. It may be necessary to apply water one or more times during warm or windy weather. Once established, irrigations can be reduced. For mature beds, water can be applied every two to three days at about 75% to 100% of ET. During cool weather, irrigation can be applied 1-2 times per week. Enough water to rewet the root system should be applied at each planting.
Vegetables
Veggies require on average about 75% to 100% of ET and must be watered regularly throughout their growth cycle to produce well. There are differences in watering requirements depending on the time of the year they are grown, the size of the plant, and the variations in length of the plant's growing seasons. Irrigate vegetable seeds, seedlings, and recent transplants frequently as they are getting established to promote uniform, healthy growth and optimum yields. Maintaining a uniform soil moisture is also important for established plants. Shallow-rooted crops will need more frequent irrigation than deep-rooted ones. Adding a layer of mulch around vegetable plantings will help maintain even soil moisture and has the added benefit of suppressing weed growth, as well. The irrigation systems recommended for use in vegetable gardens include drip irrigation, soaker hoses, or careful hand-watering. Foliage should be kept as dry as possible to reduce disease issues.
Veggies require on average about 75% to 100% of ET and must be watered regularly throughout their growth cycle to produce well. There are differences in watering requirements depending on the time of the year they are grown, the size of the plant, and the variations in length of the plant's growing seasons. Irrigate vegetable seeds, seedlings, and recent transplants frequently as they are getting established to promote uniform, healthy growth and optimum yields. Maintaining a uniform soil moisture is also important for established plants. Shallow-rooted crops will need more frequent irrigation than deep-rooted ones. Adding a layer of mulch around vegetable plantings will help maintain even soil moisture and has the added benefit of suppressing weed growth, as well. The irrigation systems recommended for use in vegetable gardens include drip irrigation, soaker hoses, or careful hand-watering. Foliage should be kept as dry as possible to reduce disease issues.
Fruit Crops
Most fruit crops require between 75% and 100% of ET to produce well. Newly planted trees will require more frequent irrigations, while established plants perform well with infrequent, deep waterings. It is useful to irrigate fruit crops using drip lines or basins. Maintaining consistent soil moisture in root zones until trees and vines become established is important, though soil can be allowed to dry out between waterings without adverse effects while plants are young. With established crops, however, water stress can cause issues with yield and fruit size. Soil moisture must be maintained while fruit is setting and growing, though soil should not be fully saturated. Mulched trees require significantly less water than trees growing in bare soil; mulch should be kept about 2-4 inches away from the trunk of fruiting trees and should be 2-4 inches thick on top of the soil. During extended periods of drought, fruiting plants are susceptible to developing issues with insect infestations and diseases if they do not receive adequate amounts of water. Although some can survive due to drought-resistance and can survive on one or two summer deep waterings, others like plums and peaches will be overly stressed. For more information on specific water needs of fruit crop species, see the individual listings in the Plant Identification modules.
Most fruit crops require between 75% and 100% of ET to produce well. Newly planted trees will require more frequent irrigations, while established plants perform well with infrequent, deep waterings. It is useful to irrigate fruit crops using drip lines or basins. Maintaining consistent soil moisture in root zones until trees and vines become established is important, though soil can be allowed to dry out between waterings without adverse effects while plants are young. With established crops, however, water stress can cause issues with yield and fruit size. Soil moisture must be maintained while fruit is setting and growing, though soil should not be fully saturated. Mulched trees require significantly less water than trees growing in bare soil; mulch should be kept about 2-4 inches away from the trunk of fruiting trees and should be 2-4 inches thick on top of the soil. During extended periods of drought, fruiting plants are susceptible to developing issues with insect infestations and diseases if they do not receive adequate amounts of water. Although some can survive due to drought-resistance and can survive on one or two summer deep waterings, others like plums and peaches will be overly stressed. For more information on specific water needs of fruit crop species, see the individual listings in the Plant Identification modules.
Landscape Trees, Shrubs, and Ground Covers
Many commonly grown woody plants and non-turf ground covers need about 50%-60% of ET once they are established. New plantings require frequent irrigation so that their root ball and the soil around it are adequately moist during the first season. In the first month, these newly installed plants may need daily waterings, lessened to 1-3 times per week for the remainder of the first year in the ground. As these plants mature, deeper and less frequent irrigation is recommended at a depth of 1-3 feet. This will encourage deep, healthy root systems to form and make them more drought-resistant as a result. Tree roots spread out laterally beyond the drip line of a tree, so they should be irrigated outward as well as downward. The objective here is to water slowly so that moisture extends into and just beyond the root zone. What will happen with established trees if they are watered for short periods of time is that they will establish more shallow root systems, which can lead to water stress more quickly in drought situations.
Every 10 to 14 days in the summertime, mature trees should receive enough water to wet most of their root zone. Lawn sprinklers will not provide enough water to adequately irrigate these trees. Trees growing in turf will need additional waterings every 4 to 6 weeks or so in the summer, depending on temperature and how much water the lawn around them is receiving. In spring and fall, trees require less water and during wintertime, irrigation can be reduced greatly. Mulch should be applied 2-4 inches thick around these plantings and be kept 2-4 inches away from plant parts. If possible, trees should be watered separately from surrounding plants, as they have very different water needs. A garden hose, micro- or mini-sprinkler, deep-root irrigator, or drip system works well for trees. Lawns and other plants should be kept at least a foot away from tree trunks to discourage waterborne disease and reduce water competition. Special considerations should be made for trees and other woody plants growing in close proximity to building walls, driveways, sidewalks, or other structures. Re-radiated heat in these situations can increase the water demand for plants. Another factor that increases water needs for established plantings is fertilizing. Avoid applying fertilizer routinely to established trees, and also avoid engaging in unnecessary pruning during times of drought, as these activities will increase water needs.
Many commonly grown woody plants and non-turf ground covers need about 50%-60% of ET once they are established. New plantings require frequent irrigation so that their root ball and the soil around it are adequately moist during the first season. In the first month, these newly installed plants may need daily waterings, lessened to 1-3 times per week for the remainder of the first year in the ground. As these plants mature, deeper and less frequent irrigation is recommended at a depth of 1-3 feet. This will encourage deep, healthy root systems to form and make them more drought-resistant as a result. Tree roots spread out laterally beyond the drip line of a tree, so they should be irrigated outward as well as downward. The objective here is to water slowly so that moisture extends into and just beyond the root zone. What will happen with established trees if they are watered for short periods of time is that they will establish more shallow root systems, which can lead to water stress more quickly in drought situations.
Every 10 to 14 days in the summertime, mature trees should receive enough water to wet most of their root zone. Lawn sprinklers will not provide enough water to adequately irrigate these trees. Trees growing in turf will need additional waterings every 4 to 6 weeks or so in the summer, depending on temperature and how much water the lawn around them is receiving. In spring and fall, trees require less water and during wintertime, irrigation can be reduced greatly. Mulch should be applied 2-4 inches thick around these plantings and be kept 2-4 inches away from plant parts. If possible, trees should be watered separately from surrounding plants, as they have very different water needs. A garden hose, micro- or mini-sprinkler, deep-root irrigator, or drip system works well for trees. Lawns and other plants should be kept at least a foot away from tree trunks to discourage waterborne disease and reduce water competition. Special considerations should be made for trees and other woody plants growing in close proximity to building walls, driveways, sidewalks, or other structures. Re-radiated heat in these situations can increase the water demand for plants. Another factor that increases water needs for established plantings is fertilizing. Avoid applying fertilizer routinely to established trees, and also avoid engaging in unnecessary pruning during times of drought, as these activities will increase water needs.
Lawns
Lawns take the most water to keep healthy out of any plantings in the garden. This is in part due to incorrect, uneven watering. Cool-season grasses like tall fescue, annual and perennial ryegrass, bluegrass, and bentgrass require 20% to 30% more water than do warm season grasses like bermudagrass, zoysiagrass, and St. Augustinegrass. Cool-season turf requires 80% (65% for minimal coverage) of ET and warm-season turf requires around 60% (36% for minimal coverage) of ET. Significant water conservation can be achieved if a cool-season grass lawn is converted to a warm-season grass lawn. For a full guide on watering lawns, see the page linked below.
Lawns take the most water to keep healthy out of any plantings in the garden. This is in part due to incorrect, uneven watering. Cool-season grasses like tall fescue, annual and perennial ryegrass, bluegrass, and bentgrass require 20% to 30% more water than do warm season grasses like bermudagrass, zoysiagrass, and St. Augustinegrass. Cool-season turf requires 80% (65% for minimal coverage) of ET and warm-season turf requires around 60% (36% for minimal coverage) of ET. Significant water conservation can be achieved if a cool-season grass lawn is converted to a warm-season grass lawn. For a full guide on watering lawns, see the page linked below.
Watering during drought restrictions
Plants that do not receive enough water will eventually show signs of water stress, like wilting, yellowing and browning of leaves, and poor fruit production. Water-stressed plants must be provided with water at an early stage of deficit to prevent irreversible damage, and it is crucial to regularly check plants for signs that they are water-stressed. These symptoms will be most noticeable in the afternoon. Symptoms to look for include:
An important phenomenon to note is temporary wilting in hot, dry days. Even when plants have enough soil moisture, they sometimes on these extremely warm days will exhibit some wilting. Roots of these plants (which tend to be broadleaf ornamentals, bedding plants, and large-leaf veggies like cucumber and squash) cannot physically take in enough water quickly enough to replenish what is lost through stoma on leaves. Affected plants will recover when temperatures cool down in the evening and overnight. Adding additional water to these plantings will not correct the problem, and it may saturate the soil so much that plants are deprived of oxygen. There are other ailments that can mimic water stress in plants, such as verticillium or fusarium fungal infections, or other plants and diseases that damage plant vascular and root systems. Checking soil moisture in the root zone of the pant is necessary to determine whether wilting is due to water stress or these other issues. If soil is moist or the plant does not respond to watering within a day, other causes of wilting may be at work.
Under drought restrictions, plants may begin to get water-stressed, though most mature perennial plants can and will survive short periods on lower amounts of water, especially if adequate amounts of water are applied during the other seasons of the year. Mature trees can survive one season with only one or two deep waterings to 1-2 feet deep towards the drip line, though they will endure severe drought stress and even death if two years pass on this minimal watering schedule. Drought-stressed trees are very susceptible to damage from diseases and insects. Fruit and nut trees grown for harvesting will not produce nearly as much during years of drought as they will in normal watering years. The main goal with these trees is to simply keep them alive during the drought years; harvesting can wait until water is more available.
Under drought restrictions, plants may begin to get water-stressed, though most mature perennial plants can and will survive short periods on lower amounts of water, especially if adequate amounts of water are applied during the other seasons of the year. Mature trees can survive one season with only one or two deep waterings to 1-2 feet deep towards the drip line, though they will endure severe drought stress and even death if two years pass on this minimal watering schedule. Drought-stressed trees are very susceptible to damage from diseases and insects. Fruit and nut trees grown for harvesting will not produce nearly as much during years of drought as they will in normal watering years. The main goal with these trees is to simply keep them alive during the drought years; harvesting can wait until water is more available.
Most established shrubs will be able to hang on through long periods of dry soil. Thorough springtime waterings and one or two deep waterings in summertime should be sufficient to keep them alive and performing well for at least one season. Established warm-season grass lawns will go dormant in the summertime if water is not adequate, but will rebound with lush growth when rainfall increases. They can survive on 20%-30% of optimal water requirement for moderate periods of time. Cool-season grasses will show drought symptoms earlier; they require about 20% to 30% more water than warm-season grass lawns. These lawns will enter dormancy quicker and thin out under prolonged water stress. The recovery of these lawns is directly related to how long they were drought-stressed. Other groundcovers can survive on about half of the amount of water they would normally receive under optimal conditions, although some dieback can be expected. These plants should be watered at least once every 3-6 weeks from the months of April through September. Large beds with vegetables or annuals (or a combination) are tough to keep alive during drought restrictions, as these plants require more water than others. It may be necessary during times of drought to sacrifice these plantings or reduce their size in order to allow available water to be directed to more valued or expensive long-term perennial plantings.
graywater use in landscapes
In California, the use of graywater to irrigate landscapes is growing in popularity. The term graywater refers to wastewater from clothes washing machines, bathtubs, showers, and sinks (and excludes wastewater from toilets, kitchen sinks, and dishwashers). Under our safety code, graywater is defined as:
"Untreated wastewater that has not been contaminated by any toilet discharge, has not been affected by infectious, contaminated, or unhealthy bodily wastes, and does not present a threat from contamination by unhealthful processing, manufacturing, or operating wastes."
- Health and Safety Code 17922.12
- Health and Safety Code 17922.12
The use of graywater is considered a green alternative to irrigating landscapes with water out of the faucet, and can lower water bills dramatically (depending on how much water you're using to irrigate your property). About 90 gallons of graywater are produced in the average household of 2.6 people each day, and while this may not be enough to irrigate all landscapes, those gardens that are low-water use without turf can be well-covered.
building runoffs and drains
planning irrigation in your landscape
How to set up a drip system
water conservation
rainwater management
importance of planting water-wise species
how to fight drought
controlling evaporation
importance of planting water-wise species
how to fight drought
controlling evaporation
pools, ponds, and water features
water for insects and wildlife
plants for around pools
water-loving plants for naturally damp areas
plants for around pools
water-loving plants for naturally damp areas