On April 8, there will be seminars conducted on fruit trees at the orchard by master gardeners from 9 a.m. to noon. Topics covered will include how to thin fruit trees for better fruit, how to prune grapes, how to fertilize fruit trees, and other matters. While there, pick up some wood mulch for free. Classes are free, as well.
Mulch nondesert plants in preparation for summer heat. Mulch is a woody material that shades the soil, such as ground wood chips. Cover bare soil with mulch to reduce weed problems and conserve water. Mulch fruit trees and trees and shrubs in bed areas. Aerate lawns now to prepare for deeper rooting of lawn grasses and improved drought and heat tolerance. Lawn fertilizers containing potassium are known to improve drought tolerance.
This is a great time to aerate lawns. Aerate a day after you water. If you're applying a lawn fertilizer now, then apply one containing slow release nitrogen, moderate phosphorus and high potassium.
This type of fertilizer would benefit lawn grasses now particularly after aeration. If you applied a fertilizer to the lawn and you use a mulching mower, then you can wait until Labor Day to fertilize, but not to aerate.
Dandelion control in lawns should be done before it gets too hot. Once it gets hot, they are difficult to control with weed killers. You do not need to apply a weed killer to the whole lawn. A spot applicator, either as a watering can or a spray bottle, will work just fine and reduce pesticides applied to the lawn and exposure to animals.
Question: During the winter, I deep watered my fruit trees monthly. The rest of the property is on a drip system for desert landscaping. How often should I deep water the fruit trees in the warmer weather?
Answer: You should irrigate fruit trees with enough water to wet the soil under the canopy of the tree to a depth of 18-24 inches each time you water. In a basin at the orchard, this takes about 15 to 20 gallons each time we water.
This would be the same amount for established trees with drip irrigation. The difference would be that the drip irrigation should be applying water to the trees in at least four locations around the basin. These would be placed in a square pattern with the emitters in the corners of the square and about 2 feet from the trunk. If trees are allowed to get bigger than 10-12 feet tall, then you will have to increase the number of emitters.
Begin watering once a week when they leaf out. On May 1, increase it to twice per week. Increase it to three times per week when it gets over 110 degrees Fahrenheit. Reduce it back to twice a week when it cools to below 110 degrees. Step it back down in the fall back to your winter watering schedule. Be sure to mulch your fruit trees.
Q: Are Butterfly Iris pruned like society garlic and red yuccas?
A: You just cut the leaves back, either eliminating the brown parts of the leaf or eliminating it to the ground if damaged. It is always best to leave as much of the leaf as you can so the plant can gather energy from sunlight. Leaf removal means less energy gathered and slower growth and slower accumulation of food reserves. After a few years of good growth, they can be dug up and divided, much like red yucca, which produces new plants on very short rhizomes separated by dividing individual plants. Society garlic produces a cluster of small bulbs attached to a basal plate that some regard as a rhizome. Probably more information than you wanted.
Q: I would like to know if I can get rid of zoysiagrass. When I re-seeded last spring, there must have been some seeds or the birds dropped a few.
A: Are you sure it is zoysia? I would think it is probably bermudagrass. Controlling both is about the same if using chemicals. Zoysiagrass can probably be dug up and removed, unlike bermudagrass, since zoysia is a much slower-growing grass and less invasive than Bermuda.
Repeat applications of Roundup as soon as you see it begin its growth. In flower beds and where other plants can get damaged, you would use Fusilade or Poast. Fusilade will be in the ingredients and probably not in big letters on the label. The label would probably say something like bermudagrass control, and then read the ingredients, looking for either of these two ingredients.
Q: I have three mesquite trees in my backyard that were planted about 10 years ago. They were planted around the perimeter of our quite large back yard. Their roots are now coming up in the area that we have planted grass. In one place it is actually causing the ground to heave, the root is so large. I am seeing about six other places where the roots are now starting to surface. What can I do? Can I have these roots cut out without damaging the growth of the tree?
A: That surprises me. Mesquite is not known to have invasive roots. It makes me think the roots are from another tree. Tree roots in moist soils can grow twice to three times their height. A 30-foot tree may have roots 60 to 90 feet from the trunk.
That being said, you can remove surface roots from trees in general or any other plant for that matter. Tree roots can be cut, given a chance to set up a chemical barrier after cutting to prevent infection and left uncovered for 48 hours. Soil can then be put back around the cut and the roots buried.
The only precaution I would recommend is to not remove massive amounts of roots from a tree close to the trunk such as all the roots on one side. Even though the tree may recover it, might lead to blowover in a strong wind if the tree has a full canopy.
It would be best to use a certified arborist for a job like this. You can find one by looking at ads in the phone book. Frequently they will mention if they are certified, or ask when you call.
Q: I am curious as to which zone Las Vegas falls into, 9 or 10. I know that the zones are set up based on how cold it gets. Is there one based on how hot it gets? I have tried with limited success to grow gardens here and would like to know how to pick the best plants to do so with.
A: I don't pay much attention to plant zones, but I pay closer attention to low temperature extremes more than anything else, which is more like the USDA requirement. I believe that is our most limiting factor. There are several plant zones around and so it depends which zone you are talking about.
There is the USDA plant zone that can be found at www.usna.usda.gov/Hardzone/ushzmap.html. We would have been considered to be in the 9b zone during the past 15 years, and in 8b during years prior to 1990.
In Sunset magazine's zone, we can be either in zone 11 or 12. During the past 15 years, we have been in zone 12. But before this period, we were clearly in zone 11.
There are other factors besides cold that are limiting here. After cold, I would say our next limiting factor is soil. This is why I have pushed good soil amendments such as composted manures and the like so much.
There is not enough I can say about modifying the soil with good amendments, even for cacti. After soil, I would say intense sunlight and high summer temperatures are the next limiting factors. Lastly, wind is the final major factor you must contend with when planning a garden.
Bob Morris is a horticulture specialist with the University of Nevada Cooperative Extension.
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