Hands-on pruning lessons offered

Bring your pruning shears and learn by doing. Pruning demonstrations are ongoing at the University of Nevada Cooperative Extension Master Gardener Orchard in North Las Vegas every Saturday and Tuesday from 9 to 11 a.m. now through January.

During the first couple of weeks in December we are working on peaches and nectarines. Later in the month, we will focus on apricots, plums and their close relatives. After a short lecture and seeing how it’s done, you will be paired with a knowledgeable volunteer who will coach you on where to make the right cuts.

Call the master gardener help desk at 257-5555 for directions to the Orchard.

Do you know a deserving Nevada resident who is studying horticulture at any of our institutions of higher learning and needs some scholarship money? As much as $5,000 is available for the 2008-’09 academic year thanks to the National Garden Clubs Inc. and its regional and state affiliates. For more information, contact the master gardener help line.

Q: I would appreciate receiving your info regarding the proper treatment of citrus trees in the desert. I have two grapefruit trees, a Meyer lemon and a lime tree. The grapefruit produces some fruit and the lemon produces many fruit. The lime tree does not seem to try. All of the trees are on the south side of the house and receive considerable sunshine, all day long. They are all about 7 years old and stand about 8 feet tall. All of the trees are supplied with citrus food. I believe that my problem is in pruning since I am not sure how to go about it.

A: There are three major problems that may limit citrus from producing. But first, please realize that this is not a good climate for citrus because of our cold winters. The three major problems are cold winters, damaging wind and temporary or intermittent drought. Generally speaking, pruning is not much of a problem since they don’t require a lot of it.

It sounds like the trees are planted in a location where they get some reflected heat during the winter months. This is important.

The lime is most sensitive to cold and it is also the tree you say is not producing. I think the two may be related. It should be protected from winter cold and winds.

Windy locations during fruit set and production can cause small fruit to be dropped from the tree due to a lack of pollination, desiccation from drying winds or mechanical damage. Put up some kind of wind screen.

Make sure the trees do not go through any kind of soil drying around the roots during their fruit production time. Drought will cause fruit drop. You can help prevent this by putting 3 or 4 inches of mulch around the trees to help keep the soil moist. Irrigate so that the entire root system under the canopy of the tree is wetted to a depth of 18 to 24 inches every time.

Pruning is simple. Remove branches that cross or interfere with each other. Try to maintain a dense canopy so that leaves shade the branches and the trunk as much as possible. Paint the trunk and exposed lower limbs with diluted white latex paint to help prevent sunburn.

Q: I saw a recent suggestion you gave concerning planting warm-season grasses such as St. Augustine, zoysiagrass, Bermuda grass and others. My question is the opposite, what can you do to get rid of that type of grass?

A: We live in a part of the country that professionals call the transition zone. It is a geographic band across the United States that has a climate where both warm-season grasses like Bermuda grass as well as cool-season grasses like bluegrass or tall fescue can grow. This really is not the advantage it seems since both types of grasses usually struggle in the transition zone.

In extreme northern parts of the U.S., warm-season grasses, which are tropical or subtropical in origin, will not survive due to the very cold winters. In the deep South, cool-season grasses do not survive during the summer heat. In our transition zone, cool-season grasses are weeds in warm-season lawns and warm-season grasses are weeds in cool-season lawns. You just can’t win.

It is much easier to remove cool-season grasses from warm-season lawns than it is to remove warm-season grasses from cool-season lawns.

Most warm-season lawns turn brown this time of year. As cold weather sets in, the above-ground part of the lawn dies while the roots and underground stems remain alive. The beginning of cold weather has little effect on cool-season grasses since they can usually handle the cold.

Once the warm-season lawn has turned brown for the winter, it will not be affected by weed killers. However, cool-season grasses still remaining green are killed by weed killer. The right choice in weed killers to accomplish this is very important. Put the wrong kind of weed killer on and you will kill everything.

Since cool-season lawns do not become dormant during the summer months, we cannot use the reverse technique. A different strategy has to be employed. We must focus on their weaknesses.

The usual warm-season grass is the very aggressive common Bermuda grass: the type spread by seed. A major weakness of this grass is its total lack of shade tolerance. Shading Bermuda grass makes it so weak that it cannot compete with the more shade-tolerant, cool-season grasses.

Lawns themselves shade the soil surface, so if a cool-season lawn is mowed high and kept dense, it will shade the horizontally growing Bermuda grass and prevent it from growing. This means you have to follow a good fertilizer schedule and use a good quality fertilizer.

Secondly, it is important that the irrigation system has good coverage. Systems with poor coverage will create weaknesses in the lawn where Bermuda grass will invade.

What if your lawn already has Bermuda grass in it? Those areas should be killed with an appropriate weed killer and replanted. The only time to do this would be in the early fall, some time around September and October. This will not totally eliminate Bermuda grass, but if you keep the new lawn mowed high and dense, Bermuda grass will be kept in check.

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.