Xtremehorticulture

Xtremehorticulture of the Desert

Reasons for Palo Verde Limb Dieback

Leave a Comment / borers, die back, dieback, palo verde, sunburn /

Q. The palo verde tree in our daughter’s yard looks like it has damage. The top has some dead branches in it. We have had to remove some limbs because of this problem. Can it be saved? A. There are several different kinds of Palo Verde used primarily in desert landscaping. All have tender new growth that can be severely damaged when exposed to intense sunlight. It is important these trees are pruned throughout their lives so that the tree’s canopy shades the trunk and limbs. If desert adapted trees have limbs removed that expose the trunk or large limbs to direct sunlight and sunburn, borers can be a problem in these trees such as Palo Verde and acacia             Pruning them in a fashion that exposes limbs and the trunk to intense sunlight causes damage that causes limb death that becomes visible a few years later. It’s a progression that usually starts with bad pruning practices. This progression begins when too much is removed from these trees. When too much is removed, the limbs and trunk are exposed to high intensity desert sunlight. Exposing the trunk and lower limbs to direct sunlight and sunburn can create future problems to trees like the Palo Verde.             Intense, direct sunlight on young limbs first causes a discoloration due to intense sunlight. As this direct sunlight repeats day after day, exposed areas of limbs and trunk facing the sun die. Water can’t through dead areas of the trunk and limbs.             Unless this sunburn causes severe damage, the top of the tree probably looks fine. The tree can still move water around the damaged area from roots to tree branches. The damage could be as much is 50% of the limb and trunk area and the tree looks fine. This is not Palo Verde but when the trunk and limbs are exposed to intense sunlight for a long period of time, year after year, the intense sunlight can damage or even kill the living part of the tree under the sunburned area. The beginning of this damage can be very attractive to some wood boring insects which can make the damage worse.             This damage from sunburn attracts insects such as borers that feed on living parts of the tree close to the damaged area. This feeding by borers causes even more damage that reduces water movement to the limbs. Perhaps the first year or two, trunk and limb damage goes unnoticed because the canopy looks fine. The first sign of sunburn is a discoloration or off-color to the trunk, limbs or even fruit on fruit trees.             But at some point, damage becomes severe enough that water movement from roots to the canopy is reduced.  Limbs start dying back because the tree can’t get enough water past the damage. This usually happens during the heat of the summer when demand for water is highest.             The homeowner now notices the limb death in the canopy. The homeowner removes dead limbs. This exposes the tree to more intense sunlight and further damage. Tree damage is so severe and unsightly the homeowner considers removing it. This is the tree “death spiral”.             What to do? Damage to the tree may be already extensive. Decide whether you can live with this damage or not. If not, have the tree removed. If you decide to keep the tree, then encourage it to heal as quickly as possible. Contribute to this healing by giving it enough water on a regular basis and apply fertilizer in early spring.

Reasons for Palo Verde Limb Dieback Read More »

Random Thoughts Regarding the Desert and Our Hot Summer

Leave a Comment / borers, palo verde, sunburn /

Perhaps this summer has been brutal but plants like palo verde can handle “brutal” weather.   “Native” palo verde in Arizona in bloom Be careful how these plants are pruned. The tendency is to prune them too high and this removes the shade that the tree naturally provides the trunk and limbs. Watering also helps. Plants like palo verde respond very nicely to increases in applied water very quickly..in just a few days. Water these plants with a hose to give them a shot of water and improve shading of the limbs and trunk.    Sap coming from Palo Verde. Removing too many branches and exposing too many large limbs and the trunk can lead to sun damage of this thin barked tree. Hopefully plants like palo verde were not pruned to allow excessive sunlight to shine on the trunks and limbs. Also, water in the soil helps keep limbs and the trunk from burning because these areas release water to the air and help cool the limbs and trunk through evaporation of water from microscopic holes that can open and close called stoma or sometimes called stomates. If water is restricted it cannot cool itself properly and they will burn. OR water loss can be faster than the plant can replace…as in the case of apple fruit…and burning occurs. That is a wide variety of plants to have sunburn on. Sunburn on trees is usually restricted to trees with a think bark (palo verde fits this) and a lack of shade covering the limbs and trunk. Sunburn is on the sides of the trunk and limbs that face the sun and not on the other sides in the shade. If this damage extend into the side in the shade then it is something other than sunburn that is going on.    In my opinion too many of the lower limbs were removed on this Palo Verde which can lead toward sunburn You can apply the same logic to agave and desert spoon. Not enough water can contribute to sunburn. If they are droughty then will burn more easily than if they are getting enough water.  A lack of soil improvement…poor soils that were not improved by adding compost at the time of planting…YES, this includes cacti!…may sunburn or turn yellow from intense sunlight. Sunburn comes in different degrees of severity…mild sunburn is a yellowing of leaves or fruit but not death of the plant tissues  beneath the damage. Medium damage results in yellowing with some brown or tissue death in or near the center of the yellowing…there is tissue death and this tissue death will attract bugs and other critters that sense the plant is damaged.  Borers will attack sun damaged areas on the trunk and limbs of trees These are bugs that are “decomposers” who want to break down these damaged plants and “recycle” them…naturally. The third stage is death of the tissues facing the sun, not only brown but cankered with bark or the skin dead and scaling or peeling back. This makes a pretty ugly plant. But the sides away from the sun are not damaged and the plant will survive unless some “decomposers” get in their and try breaking them down by feeding on them. Borers are in this category. They are goners if they look bad enough you cant live with them any longer. In most cases they will survive.

Random Thoughts Regarding the Desert and Our Hot Summer Read More »

Worms in Palo Verde

11 Comments / caterpillars, desert tree, palo verde, tent caterpillars /

Q. This is  a picture of the worms we find on our PaloVerde tree in the back yard.  We would like to get rid of them but do not know how.  Is there something besides spraying the whole tree which is huge, a systemic maybe,  that would do the trick and not kill the tree. They make a mess of the sidewalk and other stuff under the tree.  Any help would be appreciated. A. These critters have been reported elsewhere in the desert Southwest. Must be because of our wet spring weather. They should disappear in a matter of a week or two or less. It is a larva or caterpillar of a moth. I am not sure which one. Some caterpillars fold or roll leaves together with silk to form shelters. Others feed on leaves beneath a canopy of silk, sometimes creating “nests” in foliage, and others devour entire leaves along with stems. Your tree can get a lot of damage from these critters and still be fine. If there is enough of them you should see a lot of their poop on the ground because they eat a lot, voraciously, before they pupate and begin the change into a moth. You can spray with an organic pesticide such as BT or Spinosad but as far along as they are I think it’s a waste of money. Even if they defoliate the tree it will relief again and come back out. Relax and have a glass of lemonade but don’t put your lemonade under the tree.

Worms in Palo Verde Read More »

Stopping or Suppressing Flowering and Fruiting of Ornamentals

Leave a Comment / How to prevent flowering, mulberry, olives, palo verde, pine /

Q. Is there anything to stop or suppress flowering of a Palo Verde tree? My wife is allergic to the pollen and unless I can mitigate its effects, I guess it’s gone.  A. You are hitting on a very important topic as we convert our landscapes into water conserving desert landscapes. Before the conversion of landscapes from traditional to desert landscapes, the three biggest problem trees for allergy sufferers were mulberry, pine and olive. Olive flowers just before they begin to open Female mulberries produce only fruit. Male mulberries produce only pollen. Years ago fruitless (male) mulberry was planted because it was a great shade tree for the desert, water for landscapes was abundant and the male tree produced only pollen. Female mulberry trees made a mess on cars and sidewalks and birds who ate the fruit dropped it everywhere. Pine getting ready to release pollen from the male flowers Pine trees and olives were different. They also produced allergenic pollen but pollen and fruit were produced on the same tree; male and female trees were not separate from each other. Fruitless (and flowerless) olive was discovered, promoted and adopted as the only olive tree which could be planted in major urban centers like Las Vegas because it produced no flowers and hence no pollen. Mulberry flowers getting ready to release pollen Palo Verde produces allergenic pollen on flowers that are both male and female in the same flower. Comparing them to the above 3 trees, they are more similar to olive than pine or mulberry. There are no flowerless Palo Verde, unlike the olive. Olive fruit can sometimes be prevented by spraying the tree with a product like Florel Fruit Eliminator. (contains ethephon). This product also controls the fruiting of several ornamental plants (and sometimes the flowers) when applied just before bloom. Depending on your Palo Verde, flowering will probably be in April or May in our Las Vegas climate. You can read the label below View the Florel label I hesitate to recommend this product because if it is applied at the wrong dose it can cause leaf drop or possibly damage the tree. There is a recommended rate for several ornamental trees including olive but Palo Verde is not listed on the label. Use it at your own risk but if you are thinking about removing the tree anyway it might be worth a shot. I am not sure who sells it in Las Vegas but you cannot purchase it online.

Stopping or Suppressing Flowering and Fruiting of Ornamentals Read More »