Xtremehorticulture

Xtremehorticulture of the Desert

Privet Dieback Due to Irrigation

Leave a Comment / branch dead, brown leaves, Japanese privet, leaf drop, privet, Texas privet, twigs dead /

Q. We have had these trees in our backyard for 15 years.  All of a sudden, one has a bare spot. What might this be? I enclosed a picture. Not readers but demonstrates dieback in privet due to infrequent or shallow irrigations A. From your picture the plant looks like Japanese or Texas privet. Privets are notorious for looking pretty bad, leaf drop and twig dieback when they are not kept moist. They usually do nicely in lawns or when surrounded by other plants with a similar water requirement. Typically they do not do well in rock mulch and if the soil becomes too dry. So I usually recommend that the rock mulch environment is enhanced with wood mulch or that other plants are included around the base of the plant that require more frequent watering.

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Leaf Yellowing on Locust Possible Sunburn and Borers

Leave a Comment / black locust, dieback, Idaho locust, leaf drop, purple robe locust /

Q. Do you have idea why some many of the leaves on my locust tree are turning yellow? A. The most frequent problem with locust trees, Idaho or black locust, is borers in the trunks. This will cause exactly what you’re talking about, yellowing of leaves and leaf drop.             This is followed by branch dieback. Dieback of limbs may take a couple of seasons after the initial borer attack but if you are not looking for borer damage early, you will see leaf drop a couple of years into the attack.             Borers entered the trees usually where the tre is sunburned. This is normally on the west and south facing sides of the trunk or limbs. Horizontal limbs may be damaged on the upper surfaces as well.             Check the bark on the trunk or limbs see if it is loose. It may easily pull away from the trunk particularly on the south and west sides. Damage is usually on larger diameter parts of the tree.             Remove bark away from damage to areas and clean the damage down to fresh wood. You don’t need to paint it but if you want it painted, paint it.             Use a liquid insecticide soil drench to help protect the tree and give it a chance to recover during early stages of an attack.

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Star Jasmine Problems Mostly Soil, Mulch and Cold Related

14 Comments / bronzing of leaves, Las Vegas, leaf drop, Mohave Desert, Mojave Desert, nevada, scorching leaves, yellow leaves /

Q. What can I do to correct all the issues afflicting the star jasmine this winter? Problems with star jasmine. Most of these are caused by poor soil conditions and winter cold. Perhaps it might be not watered with enough water. A. The easiest is to not plant it. Hard to say exactly but generally I would call the problems in general, stress. The stress could have come from freezing temperatures, lack of water, poor soil or poor soil amendments such as high salts and lack of organic matter. Great place to put a star jasmine for aroma and welcome greetings to visitors.             The plant is some eastern and southern China and which means it is not from a desert and not really a desert plant. We have to adjust everything around it for that reason. It is not going to like desert soils or rock mulch for that reason. Star jasmine used as groundcover in rock mulch. I guarantee that plant HATES it there. Developed iron chlorosis due to rock mulch and poor soils.             Soils must have lots of rich soil amendment (compost) and it will really appreciate wood mulches. It does well as a groundcover but I think it is best as a north or east-facing trellised vine. Particularly near a window that can be opened in the Spring. When star jasmine is growing well and in good health the leaves should be a vibrant green.             The flowers are very fragrant so it should be planted in locations where the fragrance can be appreciated. It is an old-fashioned plant. Southerners might know it by the name “Confederate jasmine”.             It handles the cold winters well if it is not in rock mulch. At real low temperatures the leaves may get that bronzy, yellowish color that plant leaves can get when it is cold but will handle temperatures to 10F pretty easily. Citrus leaves will bronze in winter the same way.             Flood the soil with water to remove possible salts and let it drain. Add compost to the soil surface around it and water it in. Replace rock mulch with wood mulch but keep the mulch away from the stems to prevent collar rot.             Fertilize in the spring with a good quality fertilizer for flowering plants like roses. Shear off the old growth and let it regrow in good health. One time I had to cut a star jasmine used as a vine way back to get it to flower for me in a north exposure.

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Oleanders Drop Leaves in Drought. Will it Recover?

Leave a Comment / drought, drought resistance, leaf drop, leaf scorch, oleander /

Q. I read the post on your blog on oleanders with interest. I too have an issue. My five oleanders are mature (at least 20 years old) trees.  When we moved here a year ago they had not been watered.   When the water was turned on and major landscaping installed, many of the leaves turned yellow and dropped. However the trees blossomed and continued to do fine.  This is not the readers oleander but this oleander has leaf scorch and leaf drop while the oleander behind it is doing very well. Check the emitters or the source of water. This is a good sign it is getting a lack of water.             During the rains the gardener turned off the water system and sadly forgot to turn it back on. The water is of course back on but I have had to replace many bushes, although NOT the oleanders.  However they have begun to turn yellow again and are dropping leaves. There are still a majority of green leaves and the trees are about to burst into blooms. They have been fertilized, as has everything on the property, but I am baffled.  Would you be so kind as to give me your advice on what is happening and why? A. Oleanders are so extensive worldwide that no one is sure where they originated from. Their climate of origin is important because it determines under what conditions these plants perform best but we do know quite a bit about how oleanders behave with and without water.             We know that they are very drought tolerant. This means that when there is limited water, they can survive. Many plants can’t do this. Normally when drought tolerant plants first experience a lack of water the leaves will drop and the canopy will become sparse. If the water continues to be sparse the leaves they produce will be few and smaller and little new growth. They have to have a sparse canopy to survive.             However when water is present they have the potential for using a large amount of water and are not low water users. They respond to this water by growing more, setting new leaves that are quite a bit larger and shedding the old ones. The plant itself becomes denser and flowers profusely (provided they are not trimmed with a hedge shears).             Leaf drop is very characteristic in response to a drought. It is also characteristic when they receive water again after a drought. It is also characteristic of older growth to shed some leaves on older wood.             So, in a nutshell, going from drought to abundant water expect some leaf drop. And when oleander grows normally, expect some leaf drop as the plant matures but not typically as much as during dry/wet periods. So is oleander a good pool plant? No.

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Japanese Blueberry Leaves Falling and Canopy Thinning

2 Comments / canopy thinning, leaf drop /

Q. My problem is with my Japanese Blueberry trees. Leaves seem to fall prematurely, browning and yellowish. One of the trees bark is peeling off and appeared to be dry. There are no visible insects but I do not know what to find anyway. I have spent so much money on them for them to die. Please help. Not the readers but Japanese blueberries planted along a block wall. A. Japanese blueberries planted in a desert environment is like a square peg in a round hole; it will fit but you have to use a hammer. Japanese blueberries will require a soil heavily amended at the time of planting and organic mulch on the surface of the soil after planting.  It will do terribly in south or western exposures in full sun or in rock mulches.              If you planted this Japanese blueberry from a 15 gallon container then it will require about 15 gallons of water each time you water.  The amount of water must increase from this amount as the plant gets larger from year to year.              This can be accomplished by adding minutes to your existing irrigation schedule at each watering or adding additional emitters.  The frequency in the application of water, but not the number of gallons per application, will vary from season to season.              There is generally are a winter schedule, spring schedule, summer schedule, fall schedule and back to a winter schedule which means you should increase the number of times you irrigate per week about four times each year.  These schedules will coincide approximately with December 1, February 1, May 1, mid-June, mid-September and finally December 1 which completes the seasonal cycle.              Because your plant did not have the fullness that you would like, I would assume it is due to improper irrigation which may also lead to infestation with borers.  Pull off the loose bark at you see and look for damage in the wood do too boring insects.  This would include sawdust under the bark and perhaps elliptical exit holes from the trunk under the damaged area.  If the damage is more than half way around the trunk then I would replace the plant.

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Pepper Tree Losing Its Leaves and Apricot Dropping Its Fruits

Leave a Comment / California pepper tree, fruit drop, leaf drop /

This is normal fruit drop in apricot. The fruit was mature and ready to be picked and a good wind came along and blew them off of the tree during the night. Q. Our Pepper tree is losing it’s leaves and they are dropping like crazy. Can you tell me what I can do or is this normal this time of year? Also the fruit is dropping off apricot tree. A. Leaf and fruit drop can be from very similar causes, usually some form of stress. This stress can come from temperature extremes, irrigation and soil moisture extremes or wildly fluctuating soil moistures. Unlike leaves, for fruit to stay on the plant or tree the flower needs to be pollinated and the environment should be fruit-friendly.             Even though flowers are modified forms of leaves for fruit to develop then it must include the transfer of pollen from male parts of a flower to female parts of the flower. During this transfer it is best done by insects like bees in those trees and plants requiring pollination by insects (most fruit trees and vegetables).             During pollination (which can cover a period of a couple of weeks in cool weather because the flowers don’t all open at once) it is best if the weather is friendly to pollinators (good temperatures, good humidity and normal winds) as well as pollination. So when the flowers are open you hope for warm weather free from rain and storms. When these conditions vary further and further from ideal then the amount of fruit set may be diminished. Early almond drop in May due to lack of pollination. The yellow almonds have not been pollinated so no nut has formed and the whole nut drops from the tree two months before harvest.             Temperatures after fruit set can play a big factor as well. If temperatures drop really low after fruit set then this can cause fruit to drop early. Some fruit can start to develop from the flower even though it is not pollinated but this fruit will drop from the tree, usually turning yellow first before dropping. The bees may have missed this flower but the flower starts forming the fruit anyway.             Without pollination many fruits cannot develop more than just its juvenile stage and then drop. The fruit tree thins itself in this manner but not enough for our pleasure. This can be normal but should not be all of the fruit. This is called “June drop” which happens in our climate earlier, sometime in late April or early May usually. Plum fruits, if they do not get pollinated, will grow for awhile but eventually yellow and drop from the tree early while pollinated fruit (green here) will continue on to maturity.             In the case of your apricot see if it is natural thinning; small fruit yellow and drop. There should still be some fruit remaining. By the way some apricots do need pollinator trees. I do not know what variety you have but Tomcot, Perfection and Rival are three that might need a pollinator. If it set in previous years then it is a problem that occurred this year such as late freeze, poor conditions for pollination when the flowers were open, irregular watering and some others. Hopefully it is just June drop and you still have plenty of fruit left.             With your California pepper it is most likely irregular or having a streak of hot weather that the plants were not prepared for. Make sure if you get hit with hot weather out of the norm to run them through an irrigation cycle ahead of schedule.

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