Reason for pruning determines which limbs to cut

: I'm not trimming until the fall, but I would like to know how to trim shoestring acacia and Chinese mesquite.

A: You probably mean the Chilean mesquite. Both are generally pruned with the same basic principles and done during the fall or winter months. Much has to do with what you want to accomplish with your pruning. Some things you can think about when pruning are: Do you want it to grow faster and give more shade? Is it too tall and do you want it smaller? Is it just right now and you want to keep it this size? Do you want to walk or sit under it? Do you want it to shade a wall of the house and provide as much shading on the wall as possible?

First, make sure all pruning tools have been sterilized with alcohol and have been sharpened.

In shade or ornamental trees, it is important to maintain the natural shape of the tree. If no pruning is necessary, then don't prune. Pruning just because it is time to prune is wrong.

When pruning, I like to work from the bottom of the tree upwards, removing larger limbs first. Remove the lower limbs only high enough to permit whatever activities are planned under it. Lower limbs help shade the trunk and give the tree a balanced look.

Pruning creates wounds in the tree. The fewer wounds you create, the better. Remember that when you remove limbs and allow sunlight into the canopy you will stimulate new growth where limbs were removed. This will create new work for you in following years. When in doubt, do not cut.

Take a look at the ground beneath the tree at midday. If the ground has lots of speckled light filtering through the canopy to the ground, then do not remove very much. If the canopy of the tree completely shades the ground beneath it, you will need to do some thinning of branches to allow light inside the canopy. Allowing light into the center of the canopy reduces internal shading and causes subsequent limb dieback.

A dense canopy might also mean to you that you are overfertilizing and/or overwatering, which you will need to address.

Limbs need space to grow. If limbs are on top of each other or shading each other, remove one of them. Branches growing straight up, straight down, rubbing each other, broken, damaged or growing back toward the trunk all need to be removed. Remove branches back to their sources and do not leave any stubs. No pruning paint is necessary.

Q: I have a carob tree in my backyard that is full of carob right now and I have no idea what to do with it all. Do you know of anyone or a place that needs or wants them? Please let me know.

A: I have really forgotten about carob since most of the trees in Las Vegas were eliminated during the late spring freeze of 1990. This is a tree that would do well here again if it was resurrected and placed into a warm backyard. It has a great geocultural history and is even useful.

Carob is planted more in the Middle East and Mediterranean areas. The plant comes as either male or female so you have to make sure you have the female if you want the carob fruit or nut.

Carob was popular during the 1960s and '70s in the United States as a substitute for cocoa but it has lost that popularity primarily, I think, because it was promoted as a substitute for chocolate. It really has a good flavor all of its own and has many uses.

The carob fruit or nut can be ground and used as a cocoa substitute in cooking, baking, drinks and the like. Unlike cocoa, it is not bitter and has a relatively high sugar content.

This is a good tree as it has the right height for our urban landscapes, is drought tolerant, provides dense shade and looks good. If you want something different in your yard and a nice topic for discussion, get a female carob tree. Although a male tree is recommended for carob production, I have seen female trees in Las Vegas set pods without a male tree anywhere in sight.

Just a word of caution, without getting into details, the male tree in bloom has a smell that some people find disagreeable while others do not.

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 morrisr@unce.unr.edu.