Getting shade in desert will ‘cost’ you plenty of water

April 16 there will be two events at the University of Nevada Cooperative Extension Master Gardener Orchard in North Las Vegas that might interest some of you.

First we have our Egg Day. Chef Ryan Taliaferro, formerly chef with the Ritz Carlton at Lake Las Vegas, will create several dishes from locally produced eggs and show you how to make them. An egg producer will be present to talk about how eggs from small-scale producers can be much different from mass-produced eggs coming from commercial sources. Seating is limited and the event costs $25 per person. To sign up call the master gardener help line at 257-5555.

The second event is for aspiring beekeepers. We are offering a class for those wanting their own bees or just to know about honeybees and the process of beekeeping. This class is taught by beekeeper Rodney Mehring, owner of Blue Lizard Farm in Caliente, Nev. Mehring is also our beekeeper at the orchard. His class will be all day, 8 a.m.-5 p.m.; there is a class fee of $125, which includes lunch. To sign up or more information, call the master gardener help line at 257-5555.

Q: I have been asking my homeowners association for a shade tree in front of my condo. I did receive an Arizona ash, which is doing well. I want another one in my front yard. My understanding of the Arizona ash is that it is a good shade tree. After establishment it is supposed to be tolerant of less water, resist heat, wind and freezing. I truly love the African sumac but it reaches a height that the condo owner does not want and it requires pruning. What small shade tree less than 12-feet high is good for our desert surroundings?

A: I am surprised that the HOAs are not supportive of most small trees in residential landscapes. Yes, African sumac has some problems but it is a small tree, maturing at around a little more than 20 feet.

There simply are no shade trees maturing at 12 feet tall or less. When you look at the 20-foot category for small trees, the African sumac fits the definition of a small landscape tree. A general rule of thumb: When you want shade from any tree, desert or not, it will "cost" you in water. Water is used by plants to increase in height and density, thus equaling more shade.

Desert trees will survive on less water but they respond by giving less shade. You cannot just give a tree, desert tree or not, more water when it is growing and then, when it gets to the height you want, cut back on the water and have it stay the same. With less water its appearance, landscape function and acceptability will change.

This is a common misconception and we have demonstrated that through our research at the university. Both of these trees are suitable landscape trees. Both require some pruning, perhaps African sumac a bit more, but not an excessive amount unless it is done improperly. Both are about the same height when mature.

The African sumac will give more shade but it will require a bit more water. It is a bit more "messy." The ash will give less shade (filtered shade) and will withstand drought conditions (water gets turned off for an extended period) better. Which you select depends on what you are trying to achieve and the end result of planting your tree.

Q: We purchased a home two years ago with two existing magnolia trees in our front yard. The trees are about 8 feet tall, have some leaves on them but they don't look overly healthy. I've treated both trees with soil acidifier and a product that contains an insecticide and fertilizer each year. We also have an automatic fertilizer injector for the yard. Do you have any other recommendations for them?

A: I have said this before but it probably doesn't hurt to say it again. When we plant trees, shrubs or any other plant for that matter that is out-of-place in our desert environment, then it will cost us more time, energy and money to take good care of it. Magnolia is clearly out of its element here in the desert. So it will require more from you to make it healthy and keep it in good shape.

The acidifier might be of some help but you can get excellent acidification from compost and decaying organic matter such as wood mulches.

I hope they are not planted in rock mulch. That will be their doom if they are. Try adding compost around the tree and watering it in if you can. The fertilizer you're using is fine but I would also recommend an iron chelate, which contains EDDHA in the ingredients, as a fertilizer and apply it now.

You can skip the insecticide treatment. Magnolias are not a good choice for this climate and I will not give you a lot of hope in getting these to large trees. Enjoy them while you can. We don't see many large ones here for a good reason.

Q: I have to build a small raised bed for vegetables and herbs. I want to provide protection from the wind, cold and, later, the summer heat. The sun screening in the stores is the 25-30 percent type. What is the best sun screening level for sun screen?

A: We generally use about a 30 percent shade cloth for most vegetables. Even at 30 percent this is too much shade for some vegetables such as okra, which does much better in full sun. Okra originated out of the area of northern Africa that we now call Ethiopia and Eritrea. This probably explains why they don't like much shade and enjoy our full sun.

I would not go above 30 percent shade for those vegetables that we value for their flowers and subsequent fruit that develops from flowers. Decreasing light will affect flower production.

For leafy vegetables you can go higher in percent shade, perhaps in the 40 percent shade category.

Q: Do weed-and-feed products or fertilizers with insect killers affect the worms in my lawn?

A: Yes, they do, depending on the pesticide in the fertilizer. Insecticides are the worst on worms. Herbicides or weed killers are usually not as dangerous to earthworms but it really depends on the weed killer. Some pesticides can cause declining health in earthworms and impact their ability to ward off predators and diseases and impact their survival.

Q: Something is eating the leaves of my small grapefruit tree. I have checked it often to see if I could see the pest that was the culprit, even at night, and cannot find anything. What do you recommend?

A: Without seeing it I am not sure anything is eating your grapefruit leaves. Wind is the most common reason for damage to citrus leaves and it resembles feeding damage by insects. We did have some pretty good winds recently.

Wind damage looks most like tearing, shredding or ripping of leaves. I would not apply an insecticide if you are not convinced it is insect damage and then only if the damage is not recoverable by the tree without your assistance or if it interferes with fruit production.

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 email at morrisr@unce.unr.edu.