Poor irrigation usually source of lawn’s problems

: I had a gorgeous tall fescue lawn for five years. Suddenly, now I have large patches of dirt. I have reseeded the area and applied top dressing three times with no results. I aerate twice a year and have resodded the area twice. I don't know what to do except convert it to desert landscape, which I don't want to do.

A: The usual problem with parts of lawns that fail is lack of good irrigation coverage. If the same spot is being affected year after year, it is likely related to irrigation. Under these circumstances, rarely is it a disease, insect or soil problem.

Most commonly when irrigation is the problem, the lawn fails midway between the irrigation heads with the grass closest to the heads looking the best. This usually happens as weather warms up toward summer. As temperatures get hotter, under-irrigated grass turns a smoky gray-green color. This color change happens when the grass begins to wilt because of a lack of water. Usually, when we see this happen, we irrigate again to try to save the underwatered area but in the process overwater the well-irrigated spots.

There can be several reasons why irrigation systems begin to fail when previously they were just fine. Irrigation systems will fail if they are not properly maintained, if there is a change in the water pressure or if it is altered in some way, such as adding additional heads.

The nozzles that spray water from irrigation heads are engineered to operate at specific pressures and volumes of water. At these pressures and with an adequate volume of water, the distance water is thrown and its coverage over an area is pretty precise.

The last thing required is that the spacing between heads follows the manufacturer's recommendations. Sometimes, in an effort to save some money, irrigation heads are spaced too far apart and fail to fully overlap the water thrown by neighboring heads.

I suggest that you check irrigation coverage for this spot and make sure that you are covering it well when you irrigate. After you run a normal irrigation for that area (usually a total of 12-15 minutes), take a 12-inch-long screwdriver and push it into the soil in several locations, both close to the irrigation heads and throughout the problem area.

The screwdriver should penetrate easily to a depth of 8-10 inches, provided you don't hit rocks. Dry soil is hard to penetrate.

You also can check how evenly water is applied by putting cups randomly throughout the area. Run the irrigation for 15 minutes and see if the amount of water is similar in all cups.

A must for a good lawn in our climate is a finely tuned irrigation system and scheduling those irrigations when the lawn needs water. This time of year you should be able to get bare areas established from seed fairly easily.

Q: We would like to know your suggestions of fruit trees like peach, pear, apricot and almond for Southern Nevada. I have a lot of pomegranates, figs and pecan trees already. We live in Mesquite.

A: Recommendations of fruit trees should be similar for Mesquite and Las Vegas.

Good selections for apricot include varieties like Royal Rosa, Blenheim and Tilton. A great dual-purpose apricot for fruit and landscaping would be Katy.

We can produce good pears in Southern Nevada but oftentimes they may be misshapen and not quite as pretty to look at as those from California and the Pacific Northwest. I think this has to do with surface damage to the fruit as it is growing.

Misshapen fruit may be caused by windblown dirt in high-wind areas or light feeding damage by insects when the fruit is young. They may not be the prettiest to look at, but it does not affect the wonderful flavor and sweetness they produce in our climate. It adds character to an already great fruit. Bartlett pears do well here and one called Red Sensation is a very pretty Bartlett pear.

Remember that Bartletts are desert pears. If you like a cooking or canning pear, you cannot beat a Kiefer pear. It produces beautiful, large pears with a delicate flavor that is great in salads, pickled or preserved. These pears have no pests that I have found here yet.

Just about any of the almonds do well here, including Garden Prince, which has spectacular flowers as well, and Nonpareil, the dominant commercial variety grown in California.

Most peaches also do well in our climate, but those varieties that mature their fruit early avoid some of the pest problems that occur later in the season. White peaches are very popular right now and have some superb flavor.

A favorite are the donut or bagel peaches, which are novelties. They can get very sweet when left to ripen on the tree, but birds love them as well. They are 10 times better grown at home than those found at the grocery store.

Bob Morris is an associate professor with the University of Nevada Cooperative Extension. Direct gardening questions to the master gardener hot line at 257-5555 or contact Morris by e-mail at extremehort@aol.com.