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Monday, July 10, 2017

Carolina Cherry Laurel is from which state?

Q. I have several Carolina Cherry Trees in my yard.  Last year the leaves began turning brown and flake off. Can you tell me why they are doing this and how I can correct the problem?
Carolina cherry laurel and leaf drop

A. Let's get one thing out of the way before we begin. It is called Carolina Cherry Laurel for a reason. This plant is native to the humid, wet climate and rich soils of the southeastern United States. It is not native to dry, deserty climate and barren soils of the southwestern United States. It struggles here compared to the Southeast. This plant requires extra care on your part when growing it here.
Carolina Cherry laurel and leaf scorch
            Add 50% decent compost to the soil mix when planting. Dig and amend a hole at least three times the width of the container. Five times is better. If this wasn’t done at the time of planting, make vertical “chimneys” 2 feet deep and 2 to 3 feet from the tree trunk. Fill these “chimneys” with compost or a 50% mixture of compost and soil.
Cherry laurel heat or water stress
            Covering the soil with rock up to the trunk is a bad idea. It will work for a few years, until the soil amendment is gone, but eventually these plants will pay the price. No, I take that back, you will pay the price. Plants that begin their name with “Carolina” or “Japanese” are going to struggle in our Mojave Desert environment.
Once in awhile someone puts it in the right location and adds enough soil amendments at planting. But it will go down with all that rock mulch around it unless compost is added regularly and watered in.
            This doesn’t mean, “Don’t plant them!”. It means be careful where in your landscape you place them and how you grow them. Plants that do not belong in the desert require more investment at planting, long-term care and money to grow them here than in their native habitat.
            After planting them in a 50% mixture of compost and soil, cover the soil beneath their canopy with wood chips 3 to 4 inches deep. Woodchips should cover an area at least equal to the canopy spread of the plant. This surface “mulch” will need a couple of inches of new mulch on top of it every three years or so. This is because the bottom layer “dissolves” or rots into wet soil beneath it over time.
            This rotting of wood chips enriches the soil it touches and adds nutrients and biological activity to it. These are important ingredients to the long-term success of “alien” plants growing in our desert environment.
            The discoloration and death along the margins of the leaves arises from a plant health problem. Improve the health of these plants and they will be more tolerant of our desert conditions. Additions of compost and woodchip mulch to the soil surface will help.
            Make sure that these plants are getting enough water from at least four locations around the trunk. These emitters should be about 18 inches from the trunk in a square pattern with the trunk at the center. They should be giving these plants enough water at each irrigation. If these are drip emitters, they should be emitting water for enough minutes to allow it to drain 18 inches deep. Depending on the emitters, this could be 30 minutes to an hour.
            Irrigation of large trees and shrubs should never be daily. Give large plants at least one day without irrigation so that water can drain from the soil and the roots can “breathe”. The roots of these plants are very susceptible to suffocation, root rot, when soils remain wet and cannot drain adequately.
            The major problems with this plant, because it is so closely related to plums and peaches, are many of the same problems as fruit trees. When I look closely at the pictures you sent, which are very good and thank you very much, I see root weevil damage on the leaf edges. These are the notches that you see on the margins. These insects feed at night and are in the soil beneath the plant. There is not much you can do about them except perhaps apply a systemic insecticide around the roots after the plant has finished blooming. Use the Bayer insecticide if you go down this route.
            I believe if these plants were in good health you would see little to none of this type of damage. I believe the plants would be very full and the leaves would appear healthy. Make sure you apply either wood chip mulch around the trees as I suggested earlier and combine that with a yearly application of a tree/shrub fertilizer in late January or early February. Only use mineral fertilizers if you have wood chip mulch surrounding the trees. Again, I repeat. This should not be bark mulch if you want to improve plant health.
            Don't get me wrong. There is nothing wrong with bark mulch. It can be very beautiful but it adds nothing to the health of the plants. It is purely decorative. Wood chip mulch, trees and shrubs that are shredded in their entirety and applied to the soil surface, improve plant health when they begin to break down/decompose a.k.a. "melt" or "dissolve" back into the soil.
            Another problem with this plant is a plant disease called shot hole fungus. We see this leaf disease on peaches and plums when our humidity is too high. In climates with higher humidity, like some of those in California, this disease can be a severe problem. In fact, varieties of peaches and plums are grown in certain areas with high humidity strictly because of this disease problem. This disease causes spotting on the leaves and sometimes the leaf margins. As this disease worsens, sections inside of the spots die and drop from the leaf leaving "shot holes". Some varieties of plants are much higher susceptible than others. If the health of the plant is improved, I am guessing this disease will disappear or minimized.
            Bottom line. Improve the soil and drainage. You can do this by drilling holes in the soil with an auger as deep as possible. Fill these holes as best you can with compost. This will improve the soil and improve drainage. Cover the soil with wood chip mulch at least 3 to 4 inches deep. Fertilize with compost this year and next year you can use a mineral fertilizer if you wish provided wood chip mulch has been on the surface of the soil for 12 months. Avoid daily irrigations.

Control Powdery Mildew Disease without Chemicals

Q. What is the best way to get rid of white powdery mildew on my Euonymous plants?

A. The best way is without using chemicals. This requires understanding the conditions which create powdery mildew. The conditions that create powdery mildew are high humidity, splashing water, shade, and lack of air movement across the leaves. Applying chemicals only circumvents the problem and doesn't find a long-term solution to the problem.
Powdery mildew on Japanese euonymous and leaf death.

If this advice is followed, there is no need for applying chemicals to control powdery mildew in our climate.

           New location? Make sure your plants are in as much sun as possible. If this is not possible, you might consider a different location for these plants or planting new ones. 

            Splashing water. Do not let water from sprinklers splash on the leaves. Prune the plant to create openings for movement of air between the leaves. If there are trees above the plants, consider removing limbs of these trees that are creating too much shade so that more light reaches the plants.
            Secondly, if these plants are receiving water from sprinklers, switch to drip irrigation. If these plans are being sprinkled with water accidentally, solve this problem so that the leaves do not receive water from sprinklers. 

            Prune for air circulation. Prune these plants deep inside their canopy and remove stems that are too close to others and allow more air movement or wind through these plants. As a last resort, you can use fungicides such as the sulfur based more copper based fungicides. Fungicides used control powdery mildew on roses should also work.

Keep Mulch Away from Trunks of Small Trees

Q. I read with interest your article in the Sunday RJ regarding the mulching of fruit trees.  The article included the comment "Mulch was kept 12 inches away from the tree trunks."  Why was that done? I recently mulched my fruit trees but surrounded the trees with red cedar mulch right up to the trunks.
This larger pine tree died because wood chip mulch was piled against the trunk.
A. It is kept away from the trunk because of people watering too often. If you are watering frequently, wet mulch against the trunk can cause a serious disease problem called collar rot. Keeping the mulch a short distance from the trunk helps keep the trunk dry.
            It doesn’t have to be a foot away. It can be 6 inches away but 12 inches is easier for most people to gauge. Once the tree is older and the bark is thicker, this is seldom a big problem. But on young trees I strongly suggest doing it.

Pines In Las Vegas With NO Irrigation! Yes, its possible.

Q. Could you please explain why the pine trees surrounding the office complex called Quail Park IV at 2820 West Charleston planted right next to the buildings and surrounded by asphalt are so huge? Where are they getting the water? 
Not on the Quail Park properties but pine surrounded by asphalt but doing well.
A. Since I cannot verify this I will only speculate. But first let me tell you about another situation. Many years ago there were pines growing along the SW corner of Sahara and the Strip. The hotel/casino that was there was long gone but the pine trees remained. No irrigation. But they survived there happily for many years.
When pine trees don't get enough water the canopy begins to look very thin, sparse growth and the top of the canopy "flattens" and doesn't get as tall as its well-watered brothers.
We had a staff member in our office under my direction whose job was to answer questions much like the Master Gardeners do now for Cooperative Extension. This was pre-1990. Her name was Hobby St.Denis and who was actually a mentor of mine very early in my career. I heard her tell people to "not water so much. Look at the pines growing at Sahara and the Strip. Those pines have not been watered for years!"

We knew about the shallow aquifer that flows from the NW of the valley to the SE. It is very shallow through much of Las Vegas. It is so shallow that parking garages on the Strip had to pump water out of the bottom levels so they didn't flood! It is so shallow at that location the pines had all the water they wanted! No irrigation.

I am guessing these pines at Quail Park are pulling water from the same aquifer. You can read some very boring research articles about this aquifer (I can say that because I was one of the authors) if you google "las vegas shallow saline aquifer" and read all about it. Be prepared for a good nights sleep!

More Advice on How to Manage Plants During the Heat

            This is the time of year we see a rise in humidity along with a threat from afternoon rains. This rise in humidity and high nighttime temperatures can also bring plant disease problems. You can do something now to prevent diseases before they occur.
Clouds building during summer monsoon in Las Vegas
            The potential for disease on plants is always present. But when the environment favors disease development, their potential becomes a reality. Two plants prone to summer diseases include lawns and tomatoes.
            Three methods used to combat summer diseases are to strengthen the plants natural defenses, improve the environment where they are growing so disease is less likely or use chemicals when “all else fails”.

Top picture is summer patch disesae on tall fescue. The bottom is summer patch disease on perennial ryegrass. This disease used to be called "frogeye" for obvious reasons in the bottom picture. This disease loves the heat and loves it more when it is humid and the grass is weak.
            Lawns. Tall fescue is prone to summer diseases if they are not healthy or watered between 6 PM and 2 AM. Summer diseases favor warm temperatures and humid conditions. If your lawn is watered and still wet when night approaches, disease is more likely. Water your lawn between the hours of 2 AM and 5 AM.
            If your lawn has not been fertilized for 2 or 3 months, apply a half rate of fertilizer early in the morning when temperatures are cooler and make sure it is immediately followed with an irrigation. 

One of the "blight" diseases on tomato. But you get the picture. These diseases love the humidity. Open the canopy, keep vines off the ground and wet the leaves ONLY early in the morning.

            Tomatoes. It may feel dry to you but inside that tangle of tomato leaves is a hot, humid jungle. Growing tomatoes upright rather than letting them sprawl on the ground reduces disease problems. Also, thinning the foliage improves air movement, reduces humidity inside that tangled mess, and reduces disease potential.
            Lightly fertilize tomato plants once a month. If you plant them in the ground and never fertilize them, chances of disease problems increase because of poor health.
            Never overdo it. A light application is all they need. Applying too much nitrogen can be just as bad as not having enough.
            Some people like to hand water their vegetables by spraying with a hose. Some people apply liquid fertilizer to the leaves. Do this early in the morning so that “tangled mess” has plenty of time to dry before nightfall.
            When all else fails, then turn to chemical protection. Fungicides for lawns and vegetables can be found at the nurseries and box stores. Make sure to read and follow the directions on the label. Applying more than recommended on the label is not better.

How to Correct Yellowing of Sago Palm

Q. Would you please tell me what to do to keep leaves on my Sago Palms from yellowing? 
This is not the readers sago palm but is representative of the kind of problem I am frequently asked about regarding this plant growing in the Mojave Desert.
A. The usual problems with sago palm in our climate and soils are very poor soils, hot exposures, irrigation problems and using the wrong kind of surface mulch around them.

Cycad or sago palm can look like this if planted in the right kind of soil and put in the right location.
Landscape exposure. Sago palms should not be planted in southern or Western exposures unless they are placed in filtered shade from large trees. They grow best in Eastern and Northern exposures. The northern exposure should not receive intense sunlight late in the afternoon. In southern and Western exposures in intense sunlight the fronds will scorch on the edges, may turn yellow, but will not grow to their full length. If this is their exposure, I would move them to a new location in mid-to-late October.

Soil improvement. Sago palm grows poorly and the fronds yellow when soils don't have any organic matter. A one half bag of compost spread around the base of the plant each year helps. If this has not been done in previous years then you might want to add compost to the soil in vertical holes placed about a foot to a foot and a half away from the Sago palm about 2 feet apart. You can use a post hole digger to dig the holes about 18 inches deep and back fill them with compost.

Irrigation. Sago palms can handle a lot of water if the soil drains easily. If the soils are slow to drain, Sago palm will get root rot and begin to yellow and the fronds will begin to scorch on the edges. Adding compost to the soil and putting in vertical holes for drainage as explained above usually takes care of the problem.

Surface mulch. Some people plant sago palm with rock applied to the surface as in a desert landscape. Sago palms do not belong in desert landscapes. They should be used in high water use landscapes with lots of organics in the soil. They are not a cactus or succulent. They should never be surrounded with rock mulch. If it is then rake away the rock from the sago palm 3 to 4 feet from the trunk and apply a layer of wood chip mulch on top of an application of compost to the soil surface.

Adding compost to the soil, vertical drain holes, woodchip surface mulch and moving the plant to a new location that is not in full sun will help this plant a lot.

Palm Fronds Browning on Multi-Trunked Tree

Q. I have two multi-trunk Palm trees in my backyard, same size. One has had brown fronds in the middle of the  main trunk  ever since it was planted 5 years age while the one on the right one has always had green fronds.  Looks like the brown fronds are now moving up the main truck.  I  fertilize each of these trees in June, July and August and each gets the same amount of water.   Looks like I am going to lose the palm.

A. The browning is a combination of water, soil nutrient and management issues.

Water. The Palm is either not getting enough water or getting watered too often. Do not water every day. If you are not watering every day but watering a few days apart or longer, then increase the number and/or the size of the drip emitters irrigating the palms. 

This is a better solution than bumping up the minutes since everything else on this valve will get an increase in water. If you find that water is running out of this area under the palm tree, then break your irrigation into 2 or 3 separate waterings within our separation between.

Soil nutrients. Either these palm trees are not getting the fertilizer they need or they have been fertilized but you're not getting much of a good response. Put about 2 cubic feet of compost under the tree and water it in with a hose. Putting some iron chelate under the compost before you water it in. 

These palms will do much better if the soil surrounding their roots is covered with 3 to 4 inches of wood chip mulch. This is not bark mulch but woodchip mulch. The woodchip mulch will begin to dissolve into the soil and add organics. So will the compost. If you want a faster response from the compost, dig about 6 vertical holes in the soil with a post hole digger about 18 inches deep. Backfill these holes with compost and water it in thoroughly.
Woodchips laid on the soil surface and decomposing and improving the soil beneath it
Management. Notice how the fronds are not bad looking at the top but they get pretty brown and ugly closer to the ground. These palms should be pruned. Remove any fronds that are lower than horizontal. 

Remove these fronds as close to the trunk as you can. Consider skinning the palm with a linoleum knife or box cutter. This removes the base of the frond, exposes the trunk, and makes it look very sophisticated. Cutting off the bottom fronds will improve the look of these palms by exposing the trunk.

African Sumac Yellow Leaves and Leaf Drop

Q.  Here are the rest of the photos of our African sumacs with leaf drop.  Our yard is too small for me to get far enough away to get an entire tree in the photo.  Please let me know if that would help and I’ll go outside the neighborhood wall and see if I can get a photo of the entire top of the trees.  Thank you for any advice you can give us!

Readers African sumac yellowing and dropping leaves

A. The usual problem with African sumac yellowing and leaf drop this time of year is a lack of water. When these trees are planted by landscapers they frequently do not use enough drip emitters. Or when they plant them small, they use just a few emitters and no one adds more emitters as these trees get larger. During hot weather the amount of water larger trees require is considerably more than when it was growing during 90° weather. It is now 115 to 117F. And it has been very windy.

Another possibility could be watering too often. If the tree roots are in soil that is watered daily and it's not draining, the roots could suffocate. If they begin to suffocate and die they can also have yellow leaves and leaf drop. I think this possibility is less likely in your case.

There is a 3rd possibility. It is possible to water these trees daily and still not give them enough water. If the total volume of water applied is not enough to satisfy the trees demand for water, they can actually be under watered even when they are watered daily. I would add more emitters instead of increasing the number of minutes on the controller. Yes, I know it's more work but you won't be over watering everything else on that valve.

There is one way to find out. See if the soil around the tree is wet or dry. Take a steel probe that is at least 18 inches long. This can be a very long but skinny screwdriver or it can be a piece of 3/8 inch steel rebar 3 feet long. 
This screwdriver might work if it is long enough.

Push it into the soil in several locations under the canopy of the tree. If it pushes into the soil with a great deal of difficulty, then the soil is too dry. If this is the case, flood the soil under the tree with a hose or sprinkler with a good soaking that goes down at least 18 inches deep. You have the probe so you can measure how deep the water penetrates by pushing the probe in the soil. If the water is running off of the area, turn the sprinkler or hose on multiple times 30 minutes or an hour apart. I use a mechanical water timer and an inexpensive sprinkler on the end of a hose. You should see a response by the tree if the soil is dry in 7 to 14 days.
It would be like this but there would be no grass.
If the soil is too wet under the tree then of course you have to wait longer between waterings. But I tend to think it's probably not getting enough water. Covering the area of the soil under the canopy of the tree with woodchip mulch 4 inches deep helps keep the soil wet tremendously.