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Monday, December 19, 2011

Help Me Save My Lawn!

Q. I have some problems with my lawn and I sent you some pictures. I am a recent transplant here from Chicago and I am not sure how to manage this lawn and get it flush, green and thicker. The lawn has bare spots and the tree in the center of the lawn has roots on the surface of the soil. How should I repair this lawn? How do you manage a lawn here? Is this lawn savable? Was the tree planted too shallow? What is this green net in the lawn I found? I remember you said to apply fertilizer to a lawn around Thanksgiving. But during that time it was cold and the fertilizer bag says to water frequently.        

A. Thanks for sending the pictures. That really helps a lot. Yes, your grass is savable but there are some important things that you need to check out before we can proceed. I hope you understand the importance of water and if water is not applied appropriately it doesn't matter what you are trying to grow, it will not do well. The first thing you must do is check the irrigation system. These are the things that your irrigation system should do for your lawn if it is going to be successful here.

            From the look of the lawn it appears to be tall fescue. Make sure the irrigation sprinklers, pop-ups, rise 4 inches above the lawn. Some pop-up sprinklers are 2 inch, 3 inch and 4 inch. With tall fescue it is important that these are 4 inch since the lawn will be mowed at 2 inches or higher. 2 inch pop-ups are not adequate and you must replace them with 4 inch pop-ups. The pop-ups operate on a spring. You have to pull will pop up with your hands to measure the height or turn the irrigation system on.

Head to head coverage
            Next, when the irrigation system is on the water from one sprinkler should be thrown all the way to a neighboring sprinkler to get head to head coverage. 100% coverage or head-to-head is very important for sprinkler system to operate efficiently in the desert. Thirdly, when the sprinkler system is operating you should see droplets coming from the sprinkler and it should not be fogging or misting. If you see fogging or misting the from the sprinklers this is an indication that the pressure of the system is most likely too high.

Pressure regulator
            A pressure regulator would then be installed on your irrigation system to lower the pressure within the manufacturer’s suggested operating pressure which is usually somewhere around 40 or 45 PSI. Or you can replace the nozzles of the sprinkler pop-ups with pressure regulated nozzles. This may be a less expensive option for you since the nozzles are relatively inexpensive. The nozzle unscrews from the top of the pop-up. If the pressure of your system is 60 or 70 PSI you will definitely see some fogging if these are the older type nozzles. You should make sure that the nozzles are matched. This means that they all come from the same manufacturer with the same specifications or model.

            The pop-ups should be spaced such that the water from one sprinkler should be thrown far enough so that it hits the neighboring sprinkler. This is head-to-head coverage or 100% coverage. Making sure you have 100% coverage will give you better uniformity in the application of the water to your lawn.
Small triangular piece of lawn in upper right that makes the
lawn difficult to irrigate without water running into the
street, over watering the lawn or under watering the
small triangular piece

            I noticed on one of the pictures there is a small, triangular space as a part of the lawn. This will always be a problem for you since water cannot be applied efficiently and evenly to a small, oddly shaped space. The best shapes for lawns are square or rectangular since water use thrown by sprinklers in straight lines and distances varying from 10 to 18 feet depending upon the nozzle.

            As part of your maintenance program you should be checking to make sure the nozzles are not plugged and clear the grass around the nozzle. I would strongly suggest that you not let someone convince you to cut the lawn short around the nozzles instead of replacing them. Yes, this is an easy temporary and inexpensive fix to the problem that tall fescue must not be cut shorter than 1 1/2 inches or you will see weed invasion of your lawn in these areas. The principal weed that will invade your lawn in these damaged spots will be common bermudagrass.
Depressions in lawn around sprinkler due to a line trimmer
instead of replacing the two inch popup with a four inch

            Now the tree. The tree was not planted too shallow. This is an older tree. Because I could only see the trunk I could not determine what kind of tree it is but from the picture this is a tree which tends to have roots that grow toward the top of the soil. Or, the tree has never been irrigated deeply and so has grown its roots on the top of the soil where most of the water has been applied. Or, it can be a combination of the type of tree and shallow irrigations. Some trees are notorious for having shallow roots. The next question is whether the roots could be removed. This would be difficult to answer without knowing what type tree but it might be possible.

Differences in texture between a coarse textured tall fescue
like K31 and turf type tall fescue. The Kentucky 31 tall
fescue was seeded into the finer textured fescue to
save money, from an old slide of mine.
            It is also possible if the tree creates a lot of dense shade underneath it that the lawn will begin to thin due to a lack of light. In this case, the usual recommendation is to begin to remove lower limbs and thin the canopy of the tree to admit more light for the lawn. An option you might consider if you want the lawn to remain is to remove the tree. Another option if you want the tree to remain, is to remove the lawn and revert the landscape to a desert themed landscape.

            Fertilizing is different from seeding. I recommend fertilizing tall fescue with a high nitrogen fertilizer around Thanksgiving. This helps keep the lawn green through the winter months. Watering once a week after you apply a fertilizer is adequate but not adequate for seed. This is not time to seed the lawn. That has to be done when temperatures are still relatively warm but not too hot; usually from September 15 through October 15 or thereabouts.

            This time of year would be difficult to establish grass due to cold weather. You will now have to wait until around the end of February if you want to seed with tall fescue. When choosing seed to reseed the area, choose good quality tall fescue seed. It will not make much difference which seed you use but do not use inexpensive seed. Avoid K31 or Kentucky 31 tall fescue seed in this particular case. This is a pasture grass and not suitable for residential landscapes.

Plastic netting on a roll of tall fescue sod.
            General maintenance of a tall fescue lawn would be fertilizing on Labor Day, Memorial Day, Fourth of July and Thanksgiving. If you are mowing with a mulching mower and returning the clippings back to the lawn and then you can skip your Fourth of July application. The fertilizer that you use should be high in nitrogen, low in phosphorus and moderate in potassium. These represent the three numbers on the fertilizer bag. If you were to make a ratio of these numbers by taking the lowest number and dividing it into the other two the ratio should be 3:1:2 or 4:1:2. Examples might be 21-7-14; 15-5-10; 20-5-10, etc. These numbers do not have to be precise but they should generally be in those ratios.

            The green netting came with the sod when it was planted. The netting held the sod together. Do not pull on the netting. If you pull on the netting you may very well pull up the grass. Instead, cut the plastic netting and remove it. If someone pulled on the netting previously this may be a reason for the bare spots. I hope this helps answer some questions.

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