Watering, when and how much?

Watering the trees and garden at appropriate time is necessary. Over watering and under watering could lead to various problems to the trees. Here is an interesting article about watering the Garden from the book called “Water Conserving Gardens and Landscapes” by “John M O’Keefe”

     Some gardeners can tell at a glance, others examine leaves and stalks with their fingers, some push a steel rod into the ground, while others use moisture meters.  Most of us, however, develop a kind of intuitive feeling about when to water the garden.

     There is, of course, the simple and most obvious indicator of when to water.  For centuries, gardeners have just looked at the top 3 to 4 inches of soil.  If it is dry, chances are that you need to water, especially if it is the growing season.  This test applies to all soils in all climates, but it does not apply necessarily to the water-conserving garden.

     The water-conserving garden uses drought-tolerant plants that can survive very well in the top 3 or 4 inches of dry soil as long as the roots can obtain some moisture.  Also, the xeriscape garden is characterized by the extensive use of decks, walkways, and other hardscapes, and by the recommended use of drip irrigation that delivers water to the root zone.  Consequently, that centuries-old test could be wildly inaccurate.

     The essential hardiness of drought-resistant plants will give you plenty of leeway for any possible mistakes in watering far more than in a conventional garden where water-demanding plants may show signs of collapse and wilt if you forget to water them for more than one or two days.

     To organize and to carry out precise watering schedule can be confusing since there are so many variables: the nutritional and watering needs of each individual plant during each season, the age of each plant, the nature of the soil, the weather(temperature, wind, humidity), and the method of watering.  It can be sorted out, though with a little effort, and the results will be very worthwhile.

     In the water-conserving garden, the primary concern is for sufficient water to reach at least 60 percent of the plant’s root zone.  The roots of plants need water, air, and nutrients to survive and grow.  If you only water the top 12 inches of soil, then the roots will only develop in that top 12 inches.  Shallow watering keeps the roots shallow and exposes the plant to serious damage if the weather turns very hot or if you forget to water the garden.  Deep watering, however, permits the roots to penetrate to where they can tap into deep moisture reserves in the soil and enables the plants to survive hot spells or a missed watering.  Many low-water-use plants are extremely deep rooted; this allows them to endure long periods without water.

     Water moves down through the soil through progressive wetting of the soil particles.  It takes a long time for moisture to penetrate 2 or feet into the ground, which is why drip irrigate on is so effective.  The emitter on a drip system can direct the water to the root zone, so it is not necessary to soak the surrounding ground.

     The first step in setting up a watering schedule is to ask the supplier of your plants for recommendations on watering times.  The supplier should be a familiar with local soil conditions and with the drought-resistant plants that are sold in your area.  Use this advice as a guideline to set up your watering schedule, then adjust the schedule up or down as your experience dictates.  Taking into account the type of soil, the type of plants, and how much water per hour irrigation system delivers, turn on the water system or as long as you think is appropriate.  Evaluate your success by taking soil moisture samples from different areas of the garden.

     Take a soil moisture sample with a soil-sampling tube.  This is a tube with a serrated bottom edge and a T-bar handle. The tube has a cut-away portion so you can see the soil sample without having to push it out of the tube.  The tube is pushed into the ground, then twisted out.  Do not push the tube too close to the plant, or you could damage the root ball. If the soil core is moist for only the first few inches and you know that the plant roots go down at least 12 inches, the watering time needs to be increased at least 3 to 6 times longer.  Most soil-sampling tubes are 10 t0 21 inches long, but you can get extensions for some models that will give you a core sample of up to 3 feet deep.

     Some gardeners use a metal rod about a ¼ inch in diameter with a handle to check the moisture level in soil.  You also can buy a 3 foot-long lawn sprinkler handle that is available at most hardware stores for a few dollars.  Cut off the prongs of the sprinkler handle and sharpen the bottom end.  The rod will push through moist soil fairly easily, but when it reaches dry soil, it will stop.

     For large containers or raised beds, a simple moisture probe can be made from a stake of light-colored cedar redwood, or balsawood, about a 1/4 inch round and sharpened at one end.  Push the stake into the container and away from the main root ball; leave it in the ground for a few moments, then take it out.  The moisture will darken the stake.  For small containers, a pencil with the varnish or coating removed works well.


     Moisture sensor gauges are far more sopnisticated soil-sampling devices.  Several types of moisture sensors are available, both automatic and manual.  Automatic sensors are wared into the control box in an automatic irrigation system.  These sensors override the times and make the automatic irrigation system far more water efficient.

     I like the idea of soil moisture sensors and automatic controllers, but without them I grew five acres of ornamental shrubs, trees, annual, perennials, a vegetable garden, and fruit trees with a simple drip-tubing system that was attached to outside faucets.  I determined the water schedule by walking around and looking at the plants.  If they looked or felt dry.  I watered them.  With sensors and electronic controllers or timers.  I probably could have done a much better job and could have saved more water.  But even with my crude drip irrigation system.  I cut the water bill (in my case the electrical bill to run the well pumps) by 40 percent when compared to the former system of sprinkle’s, hoses, and flood irrigation.

     If you like having everything totally under control or do not have too much time available, then by all means go the automatic route.  You will get great results with minimum water use and a minimum demand on your time.

     Moisture sensors use different methods to measure moisture.  Tensiometers, for example, measure soil moisture content and vacuum and normally are used as permanent fixtures in the garden.


     If you do not have automatic controls on your irrigation system, tensiometers can still be permanently located in the garden simply check the reading on the meter to determine when to turn on the water.

     For fully automatic operation, wires connect the tensiometer to the control box or valve of the irrigation system.  There is an adjustable, magnetic switch that is mounted over the pressure gauge.  Where the needle goes past the moisture level setting that you have chosen, the magnetic switch activates the control box or valve to start the watering cycle.  In this way, the tensiometer can tell the control box to skip certain, preprogrammed watering cycles if the soil moisture is adequate.  Watering cycles also can be shortened and can save water since the tensiometer will shut down a watering cycle once sufficient moisture is indicated in the soil.

     The controller or timer on the irrigation system must be programmed differently, though, when using automatic moisture sensor control.  The controller on timer is set to water the maximum number of times available.  In this way, the controller or timer continually checks with the sensor before activating.  Only if the soil is dry will the watering cycle go forward.

     The number of moisture sensors you use is up to your budget and how many different water-demand areas you have.  With drought-resistant trees and shrubs, you may not need to use a moisture sensor, but for ground covers and shallow-rooted ornamental plants and vegetables, they can be invaluable.  To have a very economical setting, set the sensor to its lowest moisture level reading and watch plants for the first signs of moisture stress; then reset the switch so that the watering cycle starts just prior to the first stress signs.  Stress signs to lock for: leaves that lose their luster, that become a dull green color, or that take on an abnormal, gray or blue appearance.  Do not wait until the leaves wilt because the damage to the plant may be severe.

     Other moisture sensors include a manual, portable tensiometer, which is a sealed, water filled, metal tube.  With a sample tube that is supplied, you take a core sample from the soil and then put the sensor tube into that hole.  The end of the sensor has a perous, ceramic tip.  Leave the tube in the ground or about 5 minutes.  The gauge will register the partial vacuum that is created as the soil draws water from the tube through the ceramic tip.  The drier the soils, the higher the moisture tension is against which plant roots must pull in water from the soil- the drier the soil, the higher the reading on the gauge.

      Electronic moisture sensors are now available.  One type measures soil moisture through moisture pressure and temperatures; another measures the level of hydrogen (a component of water) in the soil.  For extensive landscape areas or orchards, there is a system of electronic moisture snoops called marshmallows-marshmallow sized gyosum blocks that contain electrodes.  Check with your garden supply retailer as to their availability in your area.


     A great deal of water in the soil is lost through evaporation, particularly in hot, dry climates.  The value of mulch in the garden is well known.  Mulch helps to prevent weeds; insulates the soil from temperature changes; keeps the roots moist and cool; extends the period between waterings; keeps the soil cooler in the summer and warmer in the winter; prevents valuable topsoil from drying out and blowing away; and protect; delicate plant stems.  Organic mulch, such as aged sawdust or shredded and chipped bark, even encourages earthworms to remain in the topsoil to enrich it and keep it well aerated.

     In the water-conserving garden, mulching plays a decorative as well as practical role.  By their nature, many low-water-use gardens tend to be less ”dense” and more spread out than the lush water- demanding  plantings in conventional garden.  Mulch, therefore, becomes an important decorative aspect of the water-conserving garden design and can make a dramatic visual impact in addition to saving valuable water.


     For thousands of years, people have collected rainwater and stored it in cisterns for use in dry seasons.  Rain barrels that were outside homes were in common use during much of this century.  With the rising cost and scarcity of fresh water, collecting rain is an idea whose time has come again.

     One woman in an area where the average rainfall is only 16 inches yearly collected 5,000 gallons from a 400-square foot roof.  She collected the rainwater in a 5,000-gallon pool that was 15 feet in diameter and 4 feet deep.  This pool was connected to a drip irrigation system that operated by gravity feed from the pool.

     Other ideas for reservoirs include vertical, plastic pipe tanks placed alongside the house and painted to blend in with the building(10 feet of 18-inch polyvinyl chloride(PVC) pipe holds 132 gallons of water).  The PVC pipe costs about $7 a foot, and the end caps cost about $30 each. An outlet in the bottom feeds water by gravity to the irrigation system. Used above ground swimming pools also make good reservoirs. They can be brought very cheaply; often  for nothing , if you take is down and cart it away.

    Remember, you roof must be rust-free , nor corrosive , and not painted with a lead based paint. Insert some type of T-junction or other means of choosing whether rainwater from downspouts goes to storage or in the ground. This will allow you to let the first fall of rain wash the roof and leaves of dust and debris before diverting the rain to storage. A removal filter on the downspouts and at the outlet of the storage container will keep out leaves and other debris that can turn the stored rainwater “ sour”.  It also will reduce the risk of blockage in your irrigation system.

    Rainwater also can be used to leach out sabs in small container plants. Submerge the plant in the pot in a bucket or barrel of rainwater for a few minutes; repeat several times, allowing the water to drain away each time.

    All manner of materials have been used for mulches, including compost, animal manures, leaves leaf mold, aged sawdust, richhulls, cottonseed hulls, sand, stones, gravel, wood and bark fragments and shredded newspapers. Black plastic sheeting also conserves moisture and cuts down on weeds. Also available is a polypropylene landscape fabric that is permeable to water and air; its primary purpose is to stop weeds from growing. Covering this fabric with a thin layer of organic mulch improves the appearance and slowsdown the degradation of the plastic by sunlight.

    Gravel, for example, when used as a mulch is well suited to xeriscape gardens. Whether you use gravel for a mulch or for decorative purposes, underlay it with plastic sheeting. The plastic will prevent weeds and discourage rodents. Use a gardening fork to perforate the plastic sheeting with small holes to allow rainwater to seep away; then put down the travel. Do not place gravel or small stones, however, near a grown tree; you will be removing leaves continually from the gravel. Use chopped wood bark instead; it tend to blend well with tree litter. Or grow a drought-resistant ground cover. Such as juniper (Juniperus horizontalis avs.), that tends to hide fallen leaves and twigs .Do not allow gravel or stones to touch plant stems because the reflected heat from the sun will burn the stems.

    The most commonly available mulches at nurseries and garden centers include shredded or chopped wood barld, which is natural looking and decomposes slowly, but does turn gray after exposure to the sun; aged sawdust , which does not steal nitrogen from the soil as fresh sawdust does; aged redwood dust , which is long lasting; decorative bark, which needs to be 3 to 6 inches deep to be effective and when dry, repels moisture and can blow away; and commercial compost, which usually is nutrient-rich sewage sludge that is mixed with wood by-products. Be aware that this sludge contains contaminants, such as heavy metals, especially cadmium. If you question government figures on safe contaminant levels, use organic mulch.

  Read the label on the bag of mulch, or ask the salesperson if the  mulch is composted or is a mixture of partially composted materials. Composted materials are decaying plant or animal material; as they decompose in the soil, they improve its structure.  Noncomposted materials, such as fresh wood shavings or fresh sawdust will decompose and condition the soil, out will rob your plants of needed nitrogen. If you use noncomposted material, apply a controlled release nitrogen fertilizer by mixing about 3 pounds of fertilizer tool cubic yard of noncomposted mulch. Partially composted material, such as manure, contains high levels of salts that can damage plants. Do not use partially composted material in the spring and summer; it can be used in the fall, so winter rains can wash out the salts before spring.

    Mulching is mostly common sense.  Since mulch acts as an insulator, do not apply mulch to the garden until the soil has warmed up in the spring. The best time to mulch is following a good spring rain.  In the fall, mulch will keep the soil warm, protect it from overnight frost, and extend the growing season.