There is an emotional connection to our plants. We plant them, feed them, water them, clean-up after them and worry about their growth and development - sometimes it seems a lot like what we do for our children or our pets, although to a lesser degree.  There is definitely an investment of time and resources that goes into gardening.

It is tempting to pamper our plants through frequent fertilizing and watering to ensure that they grow big and lush.  It understandably gives us a lot of pleasure and sense of accomplishment to see our plants thrive and bloom, or produce a bounty of fresh juicy fruit and vegetables. But, with a drought situation, now is not the time to pamper your plants. Now, is the time for tough love.  Your plants might not like it much.  They might become "petulant" by withholding their lushness, not flowering like before or not producing as much. But, they will survive.

Most of us unknowingly over-irrigate our plants, so its ok to reduce the water you give them.  In fact, the amount of water given to plants can often be reduced by 20-40%.  Most established landscape trees, shrubs, and groundcovers, regardless of the species planted, perform acceptably well with 20-40% less irrigation than they are typically given.

To reduce irrigation with the least harm to your plants, water infrequently and deeply.  Do this by increasing irrigation runtimes and extending the number of days between irrigation events. I know this seems contrary to the idea that you should reduce the irrigation runtime and keep the same frequent irrigation interval, but this will work.

Schedule slightly longer irrigation runtimes so that the entire root zone of plants is rewetted at each irrigation; then gradually increase the interval between irrigation runtimes over a few weeks. This practice will allow you to save water while allowing your plants to adjust to a new watering regiment.  After extending the interval between irrigations, the water budgeting or seasonal adjust feature found on many sprinkler controllers can be used to fine tune runtimes and achieve optimum water conservation.

When watering, consider the root systems of your trees, plants, shrubs and lawns:

• Tall fescue lawns normally have roots 6 to 12 inches deep
• Bermudagrass and other warm season grasses are normally at least 12 inches deep
• Trees, shrubs, and groundcovers are normally found within 12 to 24 inches of the soil surface
• Vegetables vary in depth from 6 to 48 inches (a chart that shows the root depths is linked below for you)

In order to fully wet the soil without creating runoff or puddling of water, it will usually require scheduling 2 to 4 relatively short irrigation cycles of 5 to 15 minutes on each irrigation day, depending on slope, soil type, output of the irrigation system, and how much water is needed.  Splitting up the watering like this give the water a chance to really soak into the soil instead of just running off the dry surface.

Adjust the runtimes in your irrigation controller every month to account for changes in the average weather conditions.  This alone can reduce landscape water use by up to 10%.

It is important to gradually reduce the water over a few to several weeks so the plants can adjust to less water.

Try to irrigate during the very early morning hours (between 2:00 am and 6:00 am) because evaporation is lower and usually there is little, or no, wind to disrupt the pattern of sprinklers during these hours if you are watering lawns.  In addition, water pressure is a little better for irrigation systems during this time.

Night time watering in dryer areas does not normally cause greater incidence of plant disease because the humidity is relatively low.  And, contrary to common belief, midday irrigation does not harm plants.  However, It isn't effective in conserving water.

To find out how deep the water is going into the soil, take a long screwdriver (or similarly shaped tool or soil probe) and probe the soil in several spots an hour or so after an irrigation. The depth that the screwdriver or tool can be easily pushed into the soil is the depth that the water has penetrated. If deeper wetting is needed to wet plant roots, then additional irrigation cycles are needed. If the soil is wet beyond plant roots, then the runtime should be reduced.

Checking the soil moisture each day during drought - or really hot, dry days - with this technique and watching the plants for signs of wilt or water stress will enable you to see how long it takes for soil to dry to the point where water must be replaced. This is the maximum interval between irrigations for the current season.  Ideally, irrigation is applied just prior to the onset of plant stress, so schedule irrigation about one day shorter than the maximum interval.

Note: Established small shrubs or groundcover are those that have been in the ground for a period of one year or more. A tree or larger shrub must be in the ground for at least 3 years to be considered established.

To determine the root depth of your herbs & vegetables, go to: Herbs & Vegetables Root Depth Chart

 

There is some debate over what to water next after the Tree.

Ultimately, it depends on whether your focus is on food crops or on the landscape, the ease of replacement, and the expense.  I value my herbs because I cook with them, and I also want a small vegetable garden to eat from this summer (food prices will be higher). So, I plan on sacrificing bedding plants and annuals in favor of my herbs, strawberries and vegetables.  I'll use mulch, shade cloth and drip irrigation to get the most from the water I have available to me.

Generally, here is the breakdown.

The Lesser Nobles – Shrubs.

Typically shrubs planted within the past two years will require irrigation during drought, thought not as much as newly planted shrubs.  During severe drought conditions, plantings up to five or six years of age may also require supplemental water.

The Merchant Class – Perennials and Established Trees and Shrubs.

Established perennials can be kept flowering with a good drink of water every two weeks.  Many established perennials will survive a drought without any supplemental water, but there will be fewer flowers.  Mulching will reduce evaporation.

Established shrubs or trees (three years or more in the ground) can be watered deeply about once a month, especially if they are showing signs of stress.  Deep, thorough irrigations from spring through summer can be enough to keep most trees and shrubs alive when water is in short supply.  Many tree and shrub species will drop leaves or wilt under severe water shortage but will survive.  Under-watered fruit trees probably will produce less, if any fruit, but will also survive.  Once water shortages are lifted, these trees will again leaf out and produce fruit.

The Serfs – Established Lawns, Groundcovers, Containers, Bedding Plants and Annuals.

Established lawns can withstand several weeks of drought without thinning or death.  The length of time varies according to the overall health of the lawn.  Application of about one-half inch of water every two to three weeks will keep the crowns of grass alive, but won't likely green it up.

Annuals and herb plants are a lower priority because they require the most watering to keep alive and can be replaced inexpensively or can be replanted next year when adequate water is available.

P.S. Remember, The Tree is King.

It's a cruel, cruel world out there – at least it is in your garden when water usage is restricted. All those beautiful trees, plants, vegetables and lawns need watering if they are to survive.  But, what gets watered?  Tough choices have to be made.

Your garden is like a medieval realm of yore, complete with a King, lesser nobility, merchant class, and serfs.  We all know who gets the most (the King, of course) and who gets the shaft (the serfs, alas).  So, lets break it down as it applies to our gardens.

The Tree is King.  The Tree is so essential to our environment.  It gives shade, helps cool the air, provides a habitat for numerous birds, animals, insects and fungi, it produces food, and it filters and cleans the air. Trees should be watered first, especially newly planted trees because it takes years for a tree to mature and it is less easily replaced than a bedding plant. You also want to give top priority to any newly planted shrubs.  But remember, the Tree is King.

and there's the rest. . .

For more on how to care for your trees' watering needs, see UC/ANR California Garden Web - Keeping Trees Vigorous or Keeping Landscape Plantings Alive under Drought or Water Restrictions

How can homeowners drastically reduce irrigation and still maintain a viable and pleasing garden? There are many garden practices that can help conserve and maximize water use.  By implementing these, even with less water, plants are able to survive summer heat and drying winds. One effective water management strategy is irrigation by hydrozones.

Start by drawing a plan of your property indicating your trees, shrubs, annuals, lawn, a vegetable garden and other plants.  Circle and group plants with similar water needs in hydrozones.  Separate hydrozones could include lawn/turfgrass, mass plantings or annual flowers, mass plantings or perennial flowers, non-turf perennial ground covers, and individual trees and shrubs.  Not sure of your plants' watering needs?  Find out the water requirements of specific plants, by clicking on the link: http://ucanr.edu/sites/WUCOLS/.

Design a system with multiple independent zones so you can schedule irrigation according to each area's watering needs.   Use a variety of irrigation methods and convert to drip irrigation where possible.  To guide you in adjusting and resetting irrigation controllers as weather and seasons change, use UC's Easy Calculator for estimating water needs.   You can also explore that site to find out about ET zone maps (ET refers to evapotranspiration).  You'll see that Contra Costa County has 3 zones: 1,8 and 14. 

Grouping of plants with similar watering needs could also include plants with similar root depths, plants that prefer shade or full sun, or plants located on a slope.  Providing you keep your irrigation systems in good working order and with proper planning, irrigating plants according to hydrozones means plants receive only the quantity of water they need. No wasted water or overwatered plants!  

Since it is difficult to maintain large plantings of vegetables and bedding annuals during a drought,  consider reducing their size or eliminating them altogether. Doing this would allow water to be directed to more valued or expensive perennial plantings such as fruit trees which are considered a high irrigation priority.  Consider reducing your lawn hydrozone area and expand your patio or deck to allow air and water to reach the root zone of trees.

Maximize your water use in all hydrozones by following these beneficial garden practices.  Apply 2 to 4 inches of mulch to slow down evaporation, inhibit weeds and keep soil cool.  Add organic matter, such as compost to the soil.  Water established plants deeply and infrequently.  Water slowly and evenly around the drip line of trees using low pressure and applying water to a minimum of four sites around the perimeter.  To keep evaporative loss to a minimum, water early in the morning, when the wind is down and temperatures are cool.  Keep plants out of the wind. Familiarize yourself with your soil type and water infiltration rate as this will help avoid runoff.

By understanding the water needs of plants, drought gardeners can care for many types of plants, even with reduced irrigation.  Grouping plants into hydrozones and watering them according to their needs is a proven effective water management solution.

 

 

 

 

For more about evapotranspiration, see UC's Evapotranspiration and Plant Water Use