Sun, summer and inclement weather frequently force many communities to enact watering restrictions.  This places an enormous burden on lawns, shrubbery, and trees.  Dead patches on lawns and die back of weaker shrubbery will be the direct result of extended drought.  Trees that were weak before the drought may not return from winter dormancy the following spring.  This article will take an in-depth look at irrigation to help you provide the proper environment for the development, growth and recovery of your lawns and ornamental plantings.

The first step in developing a watering program is site review.  It is important to take into account such factors as sun, slope, soil composition, and general exposure.  One worst case scenario would be a sunny sloped area with rocky or sandy soil and lots of wind. You almost can’t water a location like that enough. The reverse can be equally troublesome.  A shady low area with rich soil and little wind may stay continuously moist without irrigation.  Moss growth, and disease problems will be a problem here.  If you are watering manually you’ll need to prioritize. It may be too time consuming to water the entire lawn twice a week.  The sunny areas should get watered first, and you may want to maintain only the front in times of drought.

Calibration is an extremely important aspect of a proper irrigation program.  By investing a little time in calibrating your sprinkler or sprinkler system you will get much better results while saving lots of time and water.  The length of time you run your sprinkler or system is a factor of water pressure, sprinkler type and sprinkler number.

To calibrate a single sprinkler, simply place the sprinkler on the lawn with a coffee can about 5-10 ft away.  Open the valve all the way and run the sprinkler for 1/2 hour. Measure the depth of your catch, and extrapolate or interpolate to determine how long it takes to catch 1/2 or 3/4″ of water.  For those of you with irrigation systems you will need to calibrate each zone, varying the delivery time depending on site conditions and the number of heads.  A zone with 8 heads will have to run longer than a zone with 6 heads under the same site conditions.

Some general guidelines are to apply 1 1/2 to 2 inches of water per week.  This can be accomplished by watering 3/4″ to 1″ twice per week manually, or 1/2″ to 3/4″ every day with a system.  For many of us the best time to water is “when you have the time”.  Ideally however, it is best to water at around 5:00 in the morning.  Watering at night can produce a favorable environment for disease growth and should be avoided if possible.  Water between late May and September, natural environmental conditions are usually sufficient for the remainder of the year.  It is important to experiment with your lawn.  Start by using the general guidelines I’ve discussed.  Try it for a few weeks and make adjustments as needed.  You may find an area that thrives with daily watering or one that needs water only in times of drought.

Without adequate moisture a lawn will go dormant during the heat of summer.  I regularly receive calls from customers who have an irrigation system yet still have brown spots showing up in mid-summer.  Invariably the problem is locally dry areas.  Not all sprinkler systems are perfect.  If a specific areas does not get adequate coverage it will show during drought.  To check specific areas place a can on the brown area, and another one where it is green.  Run the system and compare.  Another dead give away of sprinkler system problems are lush green circles around the sprinkler heads. Either you have a leaky head, or possibly the water pressure is not sufficient to throw the water a great distance.  Summer dormancy is very common. Lawns almost always recover on their own by late September. However, they must receive some water even when dormant.  The extended drought of ’99 permanently damaged patches on most lawns in the region.   You can prevent permanent damage by giving the lawn a good deep watering (1 1/2″) every three weeks throughout the dormant period.  To really pamper a lawn, give it a brief watering midday when temperatures exceed 90 degrees.  This will not provide the roots with moisture, but it will cool the grass to relieve damaging heat stress.

Broad-leaf ornamental plantings will actually tell you when they need water.  The undersides of the leaves are covered with tiny holes called stomas.  Water exits the plant through the stomas.  To decrease moisture loss during times of drought plant leaves will curl to protect these openings.  By curling, the plant reduces airflow across the stomas, in turn reducing moisture loss.  In general trees and shrubs have a deeper more drought tolerant root system. Deep watering every two weeks with a soaker hose should provide adequate moisture.  Water weekly during extreme periods, or if shrubbery is under three years old.

Written By: Terence Boots
Massachusetts Certified Arborist
Owner: Emerald Acres Inc.