Spotty lawn requires check of irrigation system

There are no pruning classes Saturday and Dec. 31 at the University of Nevada Cooperative Extension Master Gardener Orchard in North Las Vegas. However, if you would like to come out and help me prune on those days, I will be working on peaches and nectarines. You can get some hands-on experience at that time. I will be at the orchard those days from about 9 a.m.-1 p.m. The orchard is located 100 yards east of the intersection of North Decatur Boulevard and Horse Drive.

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 lush, 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?

A: Thanks for sending the pictures. That really helps a lot. Yes, your grass is savable but there are some important things you need to check out before you can proceed.

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.

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. Pop-ups can range from 2-4 inches. With tall fescue it is important that these are 4 inch since the lawn will be mowed at 2 inches or higher. Two-inch pop-ups are not adequate. The pop-ups operate on a spring; you have to pull the top up with your hands to measure the height or turn on the irrigation system.

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. Head-to-head, or 100 percent, coverage is very important for a sprinkler system to operate efficiently in the desert. This will give you better uniformity in the application of water to your lawn.

Third, when the sprinkler system is operating you should see droplets coming from the sprinkler. It should not be fogging or misting. If you see fogging or misting from the sprinklers, this is an indication that the pressure of the system is most likely too high.

Then, a pressure regulator should 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 (per square inch). 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, especially 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 number.

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 is 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 nozzles.

I would strongly suggest that you not cut the lawn short around the nozzles instead of replacing them. This is an easy, temporary and inexpensive fix to the problem that tall fescue must not be cut shorter than 1½ inches or you will see an invasion of weeds. The principal weed that will invade your lawn in these damaged spots will be common Bermuda grass.

Now, let’s consider 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 what I could see, I could determine that 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 so it 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. This makes it difficult to mow and unsightly. This leads to the question whether the roots could be removed. This would be difficult to answer without knowing what type of tree it is, but it might be possible.

It is also possible that if the tree creates a lot of dense shade underneath it, then the lawn will begin to thin because of a lack of light. In this case, the usual recommendation is 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. If you want the tree to remain, you can remove the lawn and put in a desert-themed landscape.

At this time of year it would be difficult to establish grass because of cold weather. You will have to wait until around the end of February if you want to seed with tall fescue. When choosing seed, 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.

General maintenance of a tall fescue lawn would require 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, then you can skip your Fourth of July application.

The fertilizer 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.

Bob Morris is a horticulture expert living in Las Vegas. Visit his blog at xtremehorticulture.blogspot.com.

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