My Japanese Privet Died

Q. I have two tree form privets; one has nearly died, and the second looks to be withering at the top.  I have 8 bush form pivots that seem relatively healthy, and 2 that have completely died with one trying to bounce back from near death.  All the trees and bushes are in the same area getting the same amount of water. There just doesn’t seem to be a reason why some die and others thrive right next to each other. 

Japanese privet dieback. Jp is a mesic plant not suitable for rock, dry or very hot locations.

A. First of all, Japanese privet, like its name suggests, is not suitable for the desert. It’s suitable for Japan and similar climates. Whenever we take a plant and grow it outside of its “comfort zone” (parts of Japan and China) we will have problems unless we take these problem areas into consideration. Plants, unlike animals, cannot move from an inhospitable place to a more h
ospitable place. We can, as all animals can, because we have legs. For this reason, it’s location, where it’s planted, is extremely important.

Japanese privet can handle the hot temperatures of southern Nevada but not dry locations. It does very well in lawns in Las Vegas.

           Do You Know What Will Happen Tomorrow?

You are looking at this plant at one point in time. You don’t know what will happen to this plant in the future; all you can do is look at its current situation and what happened to it in the past.

            Japanese privet will do okay in the desert if it receives afternoon shade, enough water and soil improvement; just like Japan. Japanese privet is what we call a “mesic” plant and must receive adequate amounts water on a regular basis. Secondly, Japanese privet performs well with amended soil and needs this soil improved on a regular basis to survive. For this reason, it doesn’t like to be surrounded by rock mulch when the amendments run out. Thirdly, it doesn’t like direct desert sunlight all day long. Particularly if surrounded by rock.

Oak Tree Dropping Leaves Continuously

Q. We have a 10-year-old live oak tree (I think it's live oak) that was established when we moved into our home last year. I noticed that it sheds leaves seemingly all year long which didn't seem right to me. It is happening very fast now and I'm really worried.

This evergreen oak has been dropping its leaves. Look for aphids in the cool spring.

A. Yes, judging from your pictures it is southern live oak and probably Texas southern live oak; maybe ‘Heritage’.

            Let's get something out of the way quickly. That's irrigation. I know it doesn't seem logical but irrigation can, and notice I said can, be the source of a lot of problems in the desert. Live oak from Texas is not a “desert tree” but for a large tree (40 to 50 feet tall) it can use much less water than some other trees around the same height, such as mulberry. It will survive in a lawn and it will survive in rock landscapes if given enough water.

Water larger plants like large trees deeper than smaller trees and shrubs. To wet the soil deeper and NOT adjust the number of minutes, add more emitters.

            Whereas mulberry might require between five and 6 feet of water under its canopy each year, Texas Live Oak can still look good with 3 to 4 feet of water applied to the same area. Watering too often, not watering often enough, giving the tree not enough water all at once, and not distributing the water over a wide enough area under the tree can cause leaf drop. When water is applied to Texas live oak, it should be applied to at least half the area under the canopy and to a depth of 2 ½ feet. It is watered again when the upper six to 12 inches starts drying.

            The usual spring problem on live oak are aphids. If heavily infested the leaves will fall or drop. Aphids becomes a lesser problem when it gets hot. Trees with leaves infested with aphids are easy to spot because aphids leave a sticky residue on the leaf surface and can cause leaf drop when they feed on plant sap. The sticky residue glistens in the sunlight. An application to the soil in the spring of a systemic insecticide like imidacloprid or a rose systemic insecticide will take care of the aphids and stop the excessive leaf drop.

Privet Tree Leaves Black Spots are Disease? No.

Q. I'm sending you a photo of a leaf from my privet tree that has some kind of fungus. Can you suggest some fungicide for me to use?

Spotting on privet leaves. It could be a disease problem but it would most likely not be
there if the tree was getting proper care.

A. I think it is just a lack of good nutrition and perhaps a lack of adequate watering rather than a disease caused by a pathogen like a fungus. Even if it were a fungus disease, it is more susceptible to disease if it is in poor health. However, too much irrigation water applied too often can look similar to this.

            Not enough water usually results in leaf drop in the early stages of stress with this tree. I will post your picture on my blog for readers to see your particular problem.

            Japanese privet does much better in mixed landscapes rather than alone in rock mulch, if you have it in rock mulch. They do not like soils that develop in a rock environment and have trouble picking up the right nutrients from these types of soils to stay healthy. Please be aware that this tree is not a desert plant so it will require more care to keep it looking good.

EDDHA found in the ingredients of an iron chelate fertilizer

            Without soil improvement you might try giving it a better fertilizer product. Fertilizers for trees and shrubs from manufacturers such as Miracle Gro, Peters, Jobe’s fertilizer spikes and others will provide better nutrition for the plant than using an inexpensive agricultural fertilizer. Add to this an iron product that contains the EDDHA chelate (look at the ingredients).

            Specialty fertilizers like these are not inexpensive. However you can save some money by not using it each time you fertilize. You can make an application and then boost plant performance by using just a little bit of nitrogen fertilizer when the plant needs it.

            But if the plant is in rock landscape you will need at least one expensive fertilizer treatment annually to improve your plant performance under the poor soil conditions of rock mulch landscapes.

Shrub Dropping Its Leaves Could Be Lack of Water

Q. A month ago we had a shrub that was seemingly healthy.  It began losing its leaves since then.  I do not know the name of this shrub but it is ten years old and planted on the north side of our home getting only the early morning sun. My question is, is there a possibility of the leaves coming back or is this shrub a goner?  

A. Couldn’t tell 100% from the picture you sent but I think it is Pittosporum. First glance at the picture looked like it went through some sort of rapid shock. That's why there is leaf drop and many of them are still green. Otherwise, the plant looks healthy except for this leaf drop.

            I think the soil got too dry for a short time and caused the leaf drop. Take a hose and soak the area at the base of the shrub twice during this next week. I think you will see it produce new leaves and start to come back within 7 to 10 days.

            Check to make sure the drip emitters are not plugged and the plant is getting water. But I think it was a short-term water problem during excessively hot weather.

African Sumac Leaf Drop

Q. My African sumac tree strips itself into a skeleton about the time it gets hot. It drops its leaves. This summer I tried to water earlier and it didn’t get as awful looking. But it is a real mess when it drops leaves.

Yellowing leaves of African sumac just before leaf drop

A. African sumac is not “dry deciduous”, which is true of plants such as the Australian bottle tree. But African sumac will drop its leaves if it does not get enough water. Either increase the frequency and amount of water during the summer months or put down a layer of water conserving mulch so the soil stays wetter when it's hot. This should help reduce leaf drop.African sumac is a "messy" tree in the landscape.

Bottle Tree Leaf Drop

Q. You told someone that a bottle tree lacked water when its leaves turned brown and fell. I have a large, Australian bottle tree that was here when I bought this house 12 years ago.  Every summer it blooms and makes seedpods that eventually fall.  It also loses leaves as the person in your article described. However, it grows new leaves so it looks eventually much as it did.

Bottle tree with one side of the tree leaf drop

A. Bottle trees from Australia are “dry deciduous” trees. In other words, during the dry season of the Australian desert they drop their leaves. When rain returns, they grow their leaves again.

If these trees get water stressed in our climate and suffer from a lack of water, they drop their leaves. They “think” they are going through a dry season so they drop their leaves to protect themselves from drought.

During the summer here, if they are not receiving enough water they will also drop their leaves. They are conditioned to drop their leaves from millennia of evolution on the Australian continent.

If you want them to keep their leaves through the summer, then give them more water or, possibly, water more often. It is hard to say which is the right thing to do but my guess is they should be given more water when they are watered.

Plants use 500 to 800% more water during the months of July and August when compared to January in our desert climate. When bottle trees mature, they develop a swollen trunk that they use for storage of water that allows them to survive periods of drought, thus their name.

Leaf Drop Can Harbor Insects, Disease

Q. Is it best to remove all the leaves from the soil after they have fallen or leave them on the soil as mulch for fruit trees? My concern is about insects that might stay there during the winter and cause damage in the spring.

fr

From reader

A. In a very general sense I have two concerns regarding leaving undecomposed leaves at the base of plants. You are right, the first one is insect problems and it's very possible some insects will overwinter under loose leaves that have not decomposed.

            Remember to pick up any fruit lying on the ground as well. Do not leave dried fruit on fruit trees because of potential insect problems.

            One insect in particular is the grape leaf skeletonizer. Don’t leave debris around the base of grape plants because of this insect problem. Make sure leaves are shredded or composted. If you have one, lawnmowers are efficient leaf shredders.

The second potential problem is disease. There are a few diseases that cut overwinter on fallen leaves. It is always better to compost or shred leaves if you're going to leave them around the base of plants. Sanitation in the garden is important.

Leaves Remain on Trees If Weather is not Cold

Q. I have two dwarf peach trees. They are still loaded with leaves. What can I do about it?

A. Nothing. Just let them drop normally. One good night of near freezing or freezing temperatures and they will drop. Prune them in mid to late January.

Normal fall leaf drop on peach

            Another method you can use to drop the leaves is to begin restricting water to the tree. If it’s possible, turn off the drip emitters or bubbler to the tree for a couple of weeks. You will not hurt the tree and you will encourage leaf drop. When the leaves begin to turn yellow resume your irrigations.

Why Are My Leaves Yellowing on Loquat?

Q. The leaves closest to the trunk of my two-year-old loquat have started turning yellow and falling off. New leaves have started to grow and they look fine. It was a 5 gal tree when I planted it. Last year the tree grew very well and produced a few loquats.This year the amount of fruit appears to have doubled but it has developed this leaf problem. 

I did some research on loquat leaves turning yellow. They suggested overwatering might be the problem.  I give it about 24 gals of water once a week. I checked the soil with a moisture meter and it does not show being wet.

A. I cannot give you any definite answers why your loquat has initiated leaf drop and yellowing of the leaves. I can tell you this; many leaves will yellow just before they drop from the tree so this type of yellowing just means that the leaves have died and will drop soon. The leaf color of loquat without chlorophyll is yellow.

When the tree has initiated the dropping of its leaves, the leaves will lose their chlorophyll and hence their green color. The remaining color after the chlorophyll has disappeared will be yellow due to the presence of carotenoid pigments which are masked by the presence of green chlorophyll.

Most likely this tree went through some sort of shock. This shock initiated leaf drop. The shock can be related to water, salts including salts from fertilizers, a light freeze, toxic chemicals or salts such as a high concentration of fertilizer applied to the leaves, etc.

The water-related problem can be from too much or not enough. For instance, if it went through a very dry spell it will drop its leaves. If the soil is too wet for an extended period, it will drop its leaves. If fertilizer was applied to close to the trunk or the rate was too high for the plant, it will drop its leaves.

There are two types of overwatering; one is related to the volume of water the plant is given while the other one relates to how frequently the water is applied. The overwatering I am talking about is applying water too often, not overwatering due to applying too much water in a single application. Once a week is not too often in my opinion unless you have a drainage problem.

If you do not think the soil has been too wet or you have not fertilized the tree by either applying fertilizer to the soil or spraying leaves, then I would just wait and see what happens.

If you applied fertilizer to the soil and you suspect the application was too strong, then flood the area with water and push the salts through the soils and away from the trunk and past the roots. That's probably the best I can do without more information.

Pick the Right Variety of Roses for the Desert

Q. I have some of these roses that are the kind that they said are ground cover type but they did very poorly in the Summer, when it was hot. Now I have planted them in the shade and they leaves are turning white then falling off. Could it be that these expensive roses from the Cal coast will not do well here? My other roses are looking great now and getting higher and higher.  These ground cover roses have never looked or done well.

A. Some of the best roses available to us are from Weeks Roses http://www.weeksroses.com/ out of Ontario, California. 

Actually this is a very good climate for roses. The very worst time of the year for them is Midsummer. When planting roses they need full sun and lots of soil amendment at the time of planting. They benefit from 2 to 3 inches of wood chip mulch on the surface of the soil surrounding the plants. 

They don't have a lot of pest problems like they would in wetter parts of the country but in the shade you might expect powdery mildew. Powdery mildew will cause the upper surface of the leaves to turn white and fall from the plant. Powdery mildew seldom occurs if roses are growing in full sun and if they are irrigated through drip irrigation, not overhead irrigation. Overhead irrigation encourages the development of powdery mildew on rose leaves and flowers.

 

Powdery mildew of roses

When selecting roses stay with recommended varieties for the desert. This list of roses can be found on the weeks roses website at http://www.weeksroses.com/_RoseInfo/climate.html

Privet Dieback Due to Irrigation

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.

Leaf Yellowing on Locust Possible Sunburn and Borers

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.

Star Jasmine Problems Mostly Soil, Mulch and Cold Related

Q. What can I do to correct all the issues afflicting the star jasmine this winter?

Oleanders Drop Leaves in Drought. Will it Recover?

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.

Japanese Blueberry Leaves Falling and Canopy Thinning

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.

Pepper Tree Losing Its Leaves and Apricot Dropping Its Fruits

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.