Tree Dieback after Converting Lawn to Desert Landscaping

Q. I am writing because of a problem I have with my 20 year old, long needled pine (I forgot the name). The needles are 6-7 inches long and fluffy.

            When I converted my lawn to drip, the pine began to turn brown in several areas.  I added more and more drippers. After four years, this poor pine, once a beautiful, fluffy tree, is now in serious trouble.

            Many small branches and a few medium sized ones have died back. Every spring, it has rallied and I think it will be okay but, by the end of the summer, it looks very sad. Is there anything more I can do to save this tree?
A. I am guessing you have Chir pine. This pine is beautiful and does very well here provided it gets enough water and at the right times. When they are growing in a lawn their roots can extend long distances from the trunk and in home yards typically close to the soil surface.

            If they were growing in a turfgrass landscape converted to desert (drip) they frequently do not get enough water after the conversion. They first suffer needle drop resulting in a thinned canopy, needle tips brown, growth slows and then limb dieback begins. I think this is what is happening to your tree all due to the conversion resulting in the big trees not getting enough water.

            The water previously supplied by watering the lawn is frequently substituted with six to eight drip emitters placed fairly close to the trunk. You will need to provide more water to the tree and in many more locations to compensate.

            These are big trees and big trees require lots of water even if they are considered lower in their water use than perhaps other large trees. There is no research to tell us how much water this tree will require during an irrigation but I would assume it would probably be in the 100 gallon range or more per irrigation, evenly distributed over its root system.

            I personally don’t think trees that get over 20 feet tall should be on drip but on bubblers with a basin (depression or moat) surrounding the trunk. This depression should be large enough to hold enough water to keep the tree in good health and penetrate to a depth of 24 inches after an irrigation.

            Some people have suggested using inline drip irrigation in concentric rings around the trunk. Perhaps. But devices do not apply water, people do and people must make the decision about how much to apply and where to apply it. Drip irrigation can be deceiving because it takes hours to irrigate instead of the minutes we are used to when we water a lawn.

            Another possible approach would be to plant other plants heavily under the dripline of the tree for additional water. No one likes to do this because you have to fight with tree roots to plant.

            To save the tree you need to be proactive now. Apply water under the canopy to a depth of about 24 inches during each irrigation. Couple this with an application of fertilizer next February. You will not see improvement at this time of year from applying more water as most trees are going into dormancy. With properly placed, deep irrigations you should see a change next year during the growing season. You should see a big change in 2013.

            As it sounds to me, if you do not change your irrigation system and how you are watering you will lose the tree. We have lost MANY trees in this valley when landscapes are converted to desert landscapes principally because the irrigation system supplied to established large trees is under engineered. Most do not understand this or will not do it right because it is “too expensive”.