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Saturday, August 20, 2016

Don't Wrap Saguaro in the Winter

Q. For several years my saguaro has been turning brown slowly but the process has speeded up this year.  I have two others, one of which I had to transplant after it grew too much for its original location, but neither of them has problems and seem to be completely healthy.  I really don’t believe I am overwatering it, but it is a possibility

Q. The last time I have seen this kind of browning on the surface of a saguaro is in a landscape where they were wrapping the Saguaro each winter in an attempt to protect it from winter cold damage. They used burlap.
            It caused a lot of surface disease problems on the cactus because of a lack of air circulation. They finally stopped doing that but the damage was already done and the surface of the cactus had a lot of brown damaged areas.
            I hope you are not doing that. If you are, stop it. Let it breathe and take your chances. I know they are expensive but wrapping them causes more damage than good.
            Make sure that water is applied to the surface of the soil surrounding out to a distance of six or 8 feet. Do not water too often. Water deeply in these areas about every 2 to 3 weeks. I would rather see it at three weeks than two weeks and actually three weeks is really too often.
            These plants store water in their fat bodies and can live on this water for a long time. When water is present they absorb it like a sponge, very quickly and that fat body swells up and expands like an accordion. That's why it's ribbed. Don't wrap it in the winter time and water it deeply and not very often.

Sudden Exposure to Full Sun May Burn Star Jasmine

Q. My next door neighbor cut down large pine trees that shaded my wall of star jasmine 2 days ago. Is there even any point in trying to rig a shade cloth to get through the rest of the summer in hopes that they can "harden off" and transition to full sun through the winter and spring next year or should I basically pronounce them dead and start the grieving process now?

Star jasmine on a wall
A. Star jasmine can handle full sun if it’s planted in good soil. But you are right, it will probably go through some shock to have it exposed to the hot sun at this time of year. I am guessing you will have some scorching of the leaves and some dieback. But I think it will rebound. You may have to cut the damaged parts back, fertilize it in October and let it regrow in the spring.
Star jasmine failing and yellowing because it's growing in poor desert soil with the surface covered in rock mulch
            At this point, I would wait and see what happens. Plant health has a lot to do with how plants handle hot weather. Plants that are not as healthy will have more difficulty during hot weather than plants which are in good health. In a contrast to this, plants that are not as healthy can grow in protected environments and still look good.
            I would encourage you to buy some decent compost and spread about an inch layer at the base of these plants and water it in. The best compost for this is at Viragrow in North Las Vegas. You can buy it by the bag for I think about $2.50 a cubic foot.
            Soil improvement will go a long way in improving plant health and their ability to withstand adverse conditions. Because of the high light intensity and warmer temperatures, they might begin to use more water in this location.
            I don't necessarily think you need to apply water daily in this spot but you may have to increase the volume of water 20 or so percent and maybe add an extra day of watering each week now. Try adding this water with a hose first but avoid daily watering If you can. Watering daily might create some problems for these plants if the soil doesn't drain very well.
            If there is no surface mulch under these plants then I would put some there. Wood mulch is better than rock mulch for soil improvement. Use a 2 to 4 inch layer. You can get it free from the University Orchard in North Las Vegas which is 100 yards east of the corner of horse drive and North Decatur and Aliante Any Tuesday, Thursday or Saturday morning.

Butterfly Bush Doing Poorly May Be Grubs in the Soil

Q. I have a butterfly bush that is struggling. It looked wonderful this past spring, now the leaves and blooms are alot smaller. There are alot of leaves turning black. The bush has full sun and 
gets watered regularly. Do you know what the problem might be?

This is from a previous question regarding the same problem on Lantana. She is pointing to grubs in the soil eating the roots and damaging the plant.
A. Check for grubs (worms) eating the roots. This is a common problem on butterfly bush this time of year. Use a liquid insecticide as a soil drench to wash the roots and kill the grubs. You can also use granular insecticides and lightly watered into the soil at the base of the plant. Look for one that is for grubs at your nursery or garden center.

Plant Replacements in the Fall or Spring

Q. I removed two Italian Cypress trees (harder project than I imagined, especially the stumps). When is a good time to replace them, how big of a hole should I dig, and how should I prepare it? 

A. I can imagine that was a very difficult job removing Italian cypress. Probably the easiest way to do it, yes I know it's already done, is to cut it off and rent a stump grinder and grind out the stumps. The wood grinding's mixed with soil makes a fabulous mulch.
            The best time to replant is in the fall months but the problem is plant selection. There is usually not much to pick from. The best stuff is gone and the nurseries don't want to be stuck with anything through the winter and availability of plants from wholesalers is limited to stuff that didn't sell. But you can still find things if you're willing to look around.
            An alternative to Italian cypress is the Skyrocket Juniper. It is hard to find but stays narrow and smaller. They used to be popular 30 or 40 years ago. This is not a desert adapted tree so it will require soil improvement and I would mulch it with wood mulch at the base on top of the soil. I have never seen it planted in our hot desert climate but I don't see a reason it won't work with some soil preparation, decent irrigation and wood mulch.

You should not have a problem planting in the same holes if the Italian cypress he removed was healthy.
            Dig a hole 3 to 4 times the diameter of the container that the plant comes in. If these holes already have quite a bit of organic matter in them... You can tell by the color... Then don't add
anything. But otherwise mix the soil you take from the hole 50/50 with compost. The best compost out there locally for doing this is Viragrow compost in North Las Vegas.
Viragrow compost available in North Las Vegas

Arizona Rosewood Is True Desert Native and Does Not Require Frequent Watering

Q. We have an Arizona Rosewood tree in our back yard. It is about 8 years old, is a double trunk tree with 4 inch circumferences on each trunk.  It stands about 12 feet tall and is about 12 to 15 feet across. One water line presently waters it 3 times a day for a total of 30 minutes and is about 15 inches from the trunks. It has been fertilized with Miracle Grow tree and shrub fertilizer
and has been treated for possible infestation of insects or grubs. 
     We have noticed that some of the leaves have been turning brown and falling from the tree. 
     Can you give some info on how many water lines it should have, what their locations should be and about how much water the tree should receive or what other problems we may be able to look for? 

A. This is the wrong irrigation schedule for Arizona Rosewood. This plant originates from the Sonoran Desert so it is a true desert plant. This means that it doesn't like frequent amounts of water in small amounts as you are giving it.
            Normal for it would be watering not very often in the winter but giving it large amounts when you do and the same amount but more often in the summer. Yes, this is a bit vague but the watering schedule you have for it now is for nondesert plants.
            With this type of schedule it is possible that it is getting water too often. It is also possible it is not getting enough water when you do water. Hard to say.
            The problem now is that this tree is accustomed to frequent watering with small amounts. Its roots have grown to favor this method of watering. At this age, this tree may have some difficulty adjusting to a new watering schedule.
            One thing we can conclude is that it is a watering problem; either too often or not enough when you do water. It is definitely not a problem of watering too often AND too much combined. If you have never added drip emitters around this tree it may be time to do so.
            I am GUESSING it is not getting enough water when you are watering. Increase the amount of water by adding more drip emitters. This is better than increasing the minutes. If you increase the minutes then EVERYTHING on that cycle will get more water, whether they need it or not and it will waste water.
            It is less likely, but possible, that the roots of the tree are getting water too often. This can cause the roots to rot particularly for many desert plants.
            If I were there I would go out to Home Depot or Lowes and get an inexpensive moisture meter for houseplants. Bring it home and push it into the soil in several locations around the tree. Use this for deciding if the plant is getting enough water or not. 
Inexpensive houseplant moisture meter that you can use outside as well to see if the soil is moist or dry before watering.

I posted this information sheet from Andrea Meckley previously.

Bermudagrass Lawn Change of Color May Be Drought

Q. We have lived in the same house in Las Vegas for the last 42 years and every June my lawn has the same problem. The lawn is a mix of common and hybrid Bermudagrass. First the grass turns grayish (in patches) and then it turns brown. It slowly comes back by September. I water according to local recommendations, use Scott's Turf builder 3 to 4 times a year and use Ortho Bug-B-Gone insect granules twice a year.
A. If this were tall fescue I might be tempted to say this is a disease problem. However, since it is a mixture of Bermudagrasses I think this is an irrigation problem. This will be particularly true if these problem areas are in the same locations every year.
Turfgrass or lawns will turn a smoky or grayish green when they are not getting enough water. This is because the leaf blade either folds in half or roles depending on the grass. This creates a different color; smoky or grayish green
            Bermudagrass in our climate doesn’t develop many insect or disease problems.
            The success of lawns in our desert climate is directly tied to the quality of an irrigation system. In technical terms we say the irrigation system should provide head to head coverage; water from a sprinkler head should be thrown far enough to reach the head to its right and it’s left. If we don’t provide this kind of uniformity in the design and installation of an irrigation system it can result in brown patches that don’t receive enough water.
A close-up of the grayish green color where the lawn is not getting enough water
            The water pressure in the sprinkler system should fall within a range recommended by the sprinkler manufacturer. If the water pressure is too high or too low it will affect the distribution of water and create browning of the lawn in the same areas year after year. Otherwise, there are sprinklers now that will lower the water pressure before the water is applied to the lawn.
Another indicator of drought or lack of water in a lawn are footprints. If you walk across grass that needs water, look behind you. If your footprints remain in the grass does not spring back quickly, the grass needs water.
            You can correct this problem in the short run by increasing the number of minutes that you apply water. This delivers more water to the dry areas. Unfortunately, it also delivers more water to the wet areas resulting in overwatering of the green areas.
            It is also a good idea to punch holes in the lawn with an aerating machine in the spring, particularly in the brown areas. This helps water to move into the soil and not run off into low spots if there are any.
            Bermudagrass is notorious for building up “thatch”. Thatch is a buildup of old grass stems and debris under the surface of the lawn but on top of the soil. Years ago this thatch was burned off of the lawn with fire. We can’t do that anymore. We must do it mechanically now.
A core aerifier for lawns pulls plugs or cores out of the lawn that are about 4 inches deep. This type of verification provides better drainage and water penetration for lawns suffering from drought
            It is important to dethatch Bermudagrass each year. This is usually done in the fall when overseeding it with a cool season grass like ryegrass to maintain a green winter lawn. If the lawn is not overseeded in the fall then thatch can be a huge problem in Bermudagrass.
D thatching machines, sometimes called vertical mowers, pull debris from a lawn which allows water to better penetrate the soil and reduces runoff.
            Making changes to the irrigation system will correct some of this problem and reduce the amount of water needed to keep the lawn green. Increasing the number of minutes you apply water during the heat of the summer should solve this problem in the short run.
            But I would combine this with lawn aerification every three or four years and dethatching every year to improve the amount of water entering the soil in the dry areas.