Depth of Rock or Wood Mulch Depends on the Size of Mulch

Q. I have been replacing gravel with wood mulch and I have to put the gravel someplace. What thickness of gravel can I place around the plants, none at the trunk, without causing damage?  Also, what is the maximum amount of wood mulch can be place around plants without being detrimental to the plant?

A. The depth of rock mulch depends on the size of the rock; the larger the rock used the deeper rock mulch can be applied. Roots need to “breathe” so there must be an exchange of gases between the roots and the air. This happens through the pore spaces in the soil.

Rock of a larger size can be used as mulch and applied more deeply than smaller rock

            Generally speaking, rock mulch is applied somewhere between 2 to 4 inches deep. If this rock mulch contains “minus” material (e.g., 1/2 inch minus, ¼ inch minus) then apply 2 to 3 inches. If the rock mulch does not contain minus material then apply it 4 inches or more.

            Course mulch without minus material can be applied right up to the trunk. Rock mulch with minus material should not.

            Most information out there tells us not to apply more than 3 to 4 inches of wood chip mulch around trees and shrubs. Where this recommended depth came from I don’t know but it is repeated over and over.

            I have no problems applying 6 inches of wood chip mulch or more around trees and shrubs provided this mulch is kept away from the trunk of the plant a distance of 12 inches during its first four or five years of growth. 

Reattach Broken Limbs Quickly

Q. My newly planted pluot tree produced one fruit this past season. I guess I pulled too hard and the branch where it was attached split. I taped the split back together with electrical tape. When can I remove it?

A. Limbs that have split will never grow back together unless you reattach the broken limbs within a few minutes after the split occurs. Once the crack or split dries, they will never “fuse” back together.

            Plants grow around wounds and surround new growth by burying this damage in older wood. If the split occurs in a strategic location that supports the weight of future limbs and fruit, it will probably never be strong enough to support increasing weight in future years.

Broken peach tree limbs due to the weight of a fruit load

            I don't know how rapidly you got the tape around the wound but if this happens again you must reattach the split tightly in a matter of a few minutes. I like to use the expandable green nursery tape that you can purchase from most nurseries are garden centers.

            I am guessing the split did not grow back together, is still there and the limb no longer structurally strong enough to support fruit or the weight of new branches growing from it. Remove the broken branch with the pruning shears and reshape the tree for future growth.

Replant Ratty looking Photinia This Fall

Q. My red tip Photinia took a beating this first summer after planting. Should I wait until its cooler and cut the down to force new growth or replace them?

A. I would wait until the beginning of October, gently lift them out of the ground, wash the soil away from the root ball, add compost to the soil used for backfilling around the roots and replant them. After replanting them, I would then cut them back to about 6 inches above the soil.

            Photinia can handle our hot desert climate with no problems provided the soil is amended with good quality compost at the time of planting. It also does not like rock mulch. Planted in rock mulch I will give it five years before it starts to look ratty.

            The problem is I don’t know how your plants were planted. Judging from the pictures you sent, the soil surrounding them does not look like it has enough amendment added or the amendment was not very good. Also, I’m not sure if you planted them at the correct depth.

            You can use the existing native soil when planting them. But you must amend this soil with about 50% good quality compost when planting them.

            The rootball taken out of the container should not be placed too deep. It should be the same level as the soil surrounding it. It is very important to thoroughly soak the soil surrounding the plant after planting several times to settle the soil.

            When digging the hole for the plant, it does not have to be deep. Dig it deep enough only to accommodate the rootball. It is far more important to dig that hole wide and amend the soil in that planting hole surrounding the roots.

            Fertilize them once a year in January and use a good quality iron chelate along with your fertilizer.

How to Transplant Joshua Tree

Q. When is the best time to transplant a Joshua tree?

A. The best time is in mid to late spring but could be done in summer. The worst times are fall and early winter months. Stay away from these time periods for planting Joshua.

Joshua tree rootball

            The biggest mistakes made on planting Joshua is watering too often. Joshua's are not the easiest plants to transplant mostly because the roots taken when harvested from the Desert are not very extensive.

            Start with a smaller plant and stake it to keep the roots from moving. Plant them the same depth as they were when they were harvested.

            Amend the existing soil with about 25% compost at the time of planting. They will benefit from improved soils at the time of planting. Water at the time of planting thoroughly and then hold off for at least three weeks before watering again.

            Water no more than about every three weeks in summer. Less often in cooler and colder weather.

Recipe for Prickly Pear Fruit (Tuna) Jam

Q. I remember that you had posted an article about making jelly/jam from the flower pods of the Indian Cactus. I have several of these cacti and would like to try making the jelly/jam. Would you please repost or send me the procedure for doing this.

A. There is a big variation in the quality of fruits produced by cactus. There are selections of Indian Fig cactus or Opuntia or Nopales that produce better quality fruit, better taste, than others. 

One way you can measure this is by bird damage. If the birds are not annihilating your cactus fruit then my guess will be the fruit is not that good. Typically, birds ravage the good ones and seldom touch the ones that are not so good. 

Bird damage to the nopal fruit (tunas) indicating they are a sweet fruit good for eating and preserving.

Sugar content of these fruits or tunas as Mexicans call them can get to a similar range as table grapes or apples. I have attached the book on it that I produced and you can download it. I will also post it on my blog for people to download.

Translated from Spanish so the English is a little awkward.

From M.V. Fernandez and J.C. Morales

University of Sonora-Hermosillo

Jam of Prickly Pear

Ingredients:

2.2 lbs (1kg) of prickly pear fruit (tunas) peeled (15 tunas approximately)

3 1/2 cups of sugar (840 g)

1 tablespoon of pectin

1 tablespoon of lemon juice

Cut prickly pears in pieces and blend only half of them. Keep the rest. (Because the seeds are very hard, I pureed all the fruit and strained the pulp.) Put blended fruit into a pan and cook over medium heat; as soon as it begins to boil, add the pectin, the sugar and the lemon juice. Keep stirring the mixture constantly with the spoon. Once it starts the first boil, while stirring, add the remaining fruit if you desire. Remove the jam from the heat when it acquires a thick consistency and when shaking pan the bottom can be seen (more or less after one hour). Put the hot jam into the sterilized container immediately. (Our test jam cooked more quickly.  Be careful not to overcook.)

Packaging and Preservation for safety

On a dry cloth, place the sterilized bottles or jars. Pour in the still hot jam, with help of a spoon, leaving a minimum space of a half inch between the mouth of the bottle and the jam. Allow some steam to escape and close it tightly to form vacuum. Let cool to room temperature and place a label in the bottle with the product name and date.

Jam will be ready for its consumption in 12 hours after it was prepared. This jam will keep for a year in a fresh and dry place. Once opened, the jam must be refrigerated and consumed in a month.

Alternative ingredients:

The lemon juice can be replaced by ¼ tablespoon of ascorbic acid or one crushed Vitamin C tablet of 500mg.

Recommendations:

To keep the jam in good condition, sterilize the bottles and the cover in the following way: wash them thorougly, retire the labels and put them to boil (with enough water so they keep cover all time) during 15 minutes counted from the first fervor or boiling. Taking off by far care, with the aid of clamps or a knife in a hand and a dry rag in the other; place the bottle and the cover on a totally dry and clean cloth (if no, the bottle can be broken). Do not touch the jam with the hands when it is still hot, since it can cause a serious burn.

To take a small taste of the jam before complete the heat treatment, take a few with a spoon, drain it in a plate, and leave it to cool completely.

Preserving Large Trees When Converting to Desert Landscaping

Q. We are planning on removing our lawn and changing over to desert landscaping but after reading your blog I am wondering how the old, large Modesto Ash trees will fare from this change? Do you think it would be an issue? I tried to find out about their root system, it seems like it is shallow, but won't that be an issue as the roots will be damaged and then covered with hot rocks?

See this posting on my blog:

http://xtremehorticulture.blogspot.com/2015/08/converting-to-desert-landscapes-can.html

Large tree suffering die back due to drought after conversion to desert landscaping

A. I am not telling you not to convert to desert landscaping but be cognizant that established trees can get hurt in the process and many landscapers do not know how to convert from lawns to desert landscaping with existing large trees. 

If you have large trees in an established landscape you have some options. 

1. Leave the lawn surrounding the big trees and remove lawn where there are no big trees. 

2. Remove lawn and spiral in-line drip tubing around the existing trees out to a distance of their drip line (spread). However, if you do this you should put this drip tubing on a separate valve and run it longer and less often than drip going to other plants. 

3. Put LOTS of plants beneath these large trees and drip irrigate them to assist the existing trees with enough water. This is above and beyond having emitters for the large trees, too. 

4. Use a lawn irrigation valve to feed bubblers to existing trees and form a basin around the trees to capture water from the bubblers. This is called basin/bubbler irrigation and is a form of flood or border irrigation. The basins must be level and flat and be three to four inches thick.

HOA Replacement Trees for Privets, Ash and Sycamore

Q. I am on our landscape committee for a Henderson, Nevada, HOA. Needing professional advice, I thought of you immediately, as a longtime resident I read your weekly column and read your blog.  This fall we are going to remove many dead and diseases trees in our small community. Mostly privets that thru the years have died after we converted to desert landscape from grass. Others are mainly Russell Ashes that are diseased and or have dead limbs and with pruning look terrible, lopsided, etc. I am without hope that with the pruning done they will ever pull out of it. The various landscapers thru the years used the ashes as replacements and as I have read in your column are no longer considered a good choice. Most of all our yards in our small community face either East or West. We have been advised to replace the trees with Fruitless Olives or Living Oak. All yards are small and have rock mulch. As many other communities we are cash poor and need to make a wise decision, because it will be expensive. We will be replacing approximately 25-30 trees. The other mature 15 yr. old trees in our landscape are sycamore and for the most part doing well, along with a few other Desert Willows,etc.  We are looking for evergreen, shade trees if possible.

Thank

you so much,

I forwarded this email to a certified horticulturist working here in southern Nevada. She has worked with plant selection for a number of years and enjoys answering this type of question.I do want to mention that sycamores are a poor choice as a landscape tree for single-story or even two-story residences. They just get too tall, they consume a lot of water and require a lot of maintenance because they are out of their climate zone. In my opinion they should not be planted in hot desert climates and desert soils. They are a larger scale tree and require big properties to look good. They do well in arid climates provided there is enough water for them. Certainly they should not be planted in large quantities.

Bob Morris

Sycamore near south facing wall with heat damage to the leaves facing the wall

A. Bob Morris forwarded your email to me.  I am Andrea Meckley, a certified horticulturist working here in the Las Vegas area since 1992.  I understand your situation with the privet trees doing poorly.  Since you are going through the expense of replacement I realize you want to make good choices.  Below are a few thoughts:

1. Fruitless Olives:

                  Pros:  evergreen,  little leave drop  

                 Cons:  slow grower,  sometimes they will fruit even though they are not supposed to.  If this happens you can apply a solution to stop them from fruiting if it concerns you.

2.  Southern Live Oak:  

                 Pros:   evergreen

                 Cons:  slow grower, debris from leaves and acorns

Between the two above I would choose the Olive.  

Since you have existing Sycamore and Desert Willow trees that are deciduous, I would also consider the following medium size evergreen and semi-evergreen trees:  Xylosma tree (Xylosma congestum), Holly Oak (Quertcus ilex), Blue Palo Verde (Parkinsonia florida) , Desert Museum Palo Verde (Parkinsonia 'Desert Museum'), Bay Laurel standard trunk tree (Laurus nobilis), and Shoestring Acacia (Acacia stenophylla) which may be a little messy.  One good source for good pictures and more information can be seen at snwa.com under 'landscapes' and then under 'plant search'.  Please contact me if you wish to discuss further.

Hope this helps. 

Andrea Meckley, CH

imn2plants@aol.com 

Trees for Privacy and Hummingbirds

Q. Putting landscape in backyard of new home in a couple of weeks what type of trees do you suggest that will give me privacy and not shed all leaves in the fall also trees and shrubs that attract hummingbirds.

I am not fond of making tree recommendations so I am ccing this to Andrea who loves to do that kind of thing. Good luck!

Bob Morris

A. I am Andrea Meckley, a certified horticulturist working her in the Las Vegas Valley in the green industry since 1992.   Attached is a Hummingbird Plant list.  Also is attached the middle pages of a publication called Trees for Tomorrow.  

Without knowing more details on the tree you want, I suggest you check it out.  I could not scan the whole list of large trees so if you need that info go to www.lasvegasnevada.gov/files/trees.pdf  That website address will also give you pics and more info on each tree.  

I assume you want a small to medium size tree.  Since you want a tree with leaves all year, start with trees labeled 'evergreen' in the 'tree type' column.  Narrow the choices depending on flowers (some debris), water use, thorns, etc. according to chart.  Also visiting demonstration gardens is a good reference tool to use in choosing plants.  We have the Springs Preserve and Master Gardner Demonstration gardens in Las Vegas and Acacia Park in Henderson.

Please Define Deep Watering

Q. Please define "deep watering." In particular, how would you describe "deep watering" a pomegranate bush with a 3" to 4" trunk?

A. Good question. I throw these terms around and I assume people know them or understand them when they don't.

            Deep watering is talking about applying enough water in one irrigation so that the entire root system becomes wet. When deep watering it is also accompanied by less frequent irrigations. This means giving the soil and roots a chance to dry somewhat before the next irrigation.

            There are two ways to water. One way is to give a small amount very often, perhaps daily or twice a day.

            The other way is to apply a large amount and then wait a long time before you give it more. The second way is preferable to the first way for plants that are deep-rooted. Deep-rooted plants are larger, woody plants such as all trees, all large and medium-sized shrubs, all woody vines, and all woody groundcovers.

            Water these types of plants deeply by applying enough water so that the applied water drains to a depth of 18 to 36 inches. The water is then shut off until that soil begins drying. Technically, the plant is not watered again until about half of the water in the soil has been used.

            When half the water is gone, water is applied again until it reaches the same depth as before. This is a continual cycle with the number of days between irrigations decreasing as it gets harder and increasing as it gets colder.

            Deep watering normally applies to woody plants but not to lawns, flowerbeds, vegetable beds and small fruits like strawberries. These are shallow rooted plants and their applied irrigation water is shallow, not deep.

 Deep watering a pomegranate that has a 1 inch diameter trunk is really no different than deep watering a pomegranate with a 3 to 4 inch trunk. Water is applied to the same depth with both of these trees. 

The difference between them is where the water is applied and the amount. In the case of a pomegranate with a 1 inch diameter trunk, we might use only two drip emitters. Two drip emitters might deliver enough water to the soil under the canopy while it is small. 

However, when the pomegranate gets to 3 to 4 inches in diameter, more emitters are needed because the larger tree requires more water. These emitters are spaced far enough apart so that the water is applied over a greater area under the canopy of the tree. The number of minutes on the irrigation clock may not of changed but the number of emitters has so the larger tree now gets more water.

Nutgrass or Nutsedge Difficult to Kill with Chemicals

Q. I have tried digging this weed up but it comes back. I have tried both Roundup and Spectracide according to the package directions, and even painting it on the foliage full strength.

Although it starts out pretty small, if I miss pulling one up, they get quite large. Any assistance in getting rid of this plant is greatly appreciated.

Judging from the roots which actually look like a rhizome I believe this is nutgrass.

A. Judging from the pictures you sent this is one of the nutgrasses or nutsedge. The roots sure look like it to me. To be sure if it is one of the sedges and not a grass, cut the top of the weed off at its stem just below the leaves. Roll the stem between your fingers and see if the stem is triangular rather than round.

            Sedges have triangular stems in cross section. Rolling the stem between your thumb and first finger you should “feel” the triangular bumps of the stem and the stem should not feel round.

Nutgrass with nut attache to the rhizome or "root".

            Sedges, like nutgrass, are more difficult to kill than grasses. Nutgrasses have underground “nuts” attached to the “roots” which are really underground stems called rhizomes. These nuts grow into new plants if they are separated from the mother plant or the mother plant is killed.

            This is why pulling, hoeing or using chemical weed killers do not work on this plant. As you have found out, spraying the tops with Roundup or dandelion killer “burn” the tops back but release the growth of the nuts.

Triangular stem of nutgrass in cross section.

            These nuts are usually anywhere from 4 to 8 inches below the soil surface. All you have done is kill the mother plant and the baby plants released from the nuts that pop from the ground grow like they are on Red Bull. Pulling nutgrass from the soil easily separates the nuts from the mother plant with the same result.

            What to do? There are two basic approaches toward getting some control. The first is soil replacement. If it’s a small area, you can dig down 12 to 14 inches deep, remove the soil and replace it with clean soil. You can take the soil and put it in a clear plastic bag in the middle of summer and “cook” it using the sun.

            You can starve out the nuts. If you continue to remove the tops at the soil surface, over and over, before they get more than two or 3 inches tall it is possible to exhaust or starve the nuts so that they die. If you pursue this option you have got to stay on top of it or it will not work

Palm Tree Roots Exposed – No Problem

Q. This is the pics of the palm tree roots. Why are the roots growing above the surface? Is it an issue and can I do anything to correct it? 

A. This is very common among palm trees and nothing to be alarmed about. You can leave them be or if you don't like the look of it then mulch the surface of the soil 5 inches deep with a wood chip mulch. The palms will benefit from that mulch. It's an aesthetic issue and not a palm tree

management issue.

Converting to Desert Landscapes Can Damage Existing Trees

Q. We removed half of our lawn with a 15 year old Chilean Mesquite in the middle which has done very well up to this point. Besides water from the lawn it had its own water supply located near the trunk. During grass removal, roots were chopped and six small plants with drip emitters in the rock mulch surrounding the tree. Will the tree be okay now that the front half sits in rock with only the plant emitters providing water.

A. The short answer is it will not. You need to supply more water to this tree or it will begin to drop its leaves and the branches will begin to die back.

Mesquite roots growing deep for water.

            Now the long answer. Chilean Mesquite is among a group of plants, called phreatophytes, which have the potential to develop a very deep root system when growing in the wild along arroyos. In the case of mesquite, 200 feet or more. This is if the tree is in the right location together with deep, infrequent rains that help establish roots to that depth. Arroyos, or desert gullies, concentrate rainwater in one location pushing water to great depths with the roots of these plants not far behind.

            Phreatophytes like mesquite when grown with water that is applied frequently grow rapidly, vigorously with a very dense canopy. In many home situations, trees do not develop deep roots because the water supplied to them, such as your lawn, is applied only to the surface few inches.

            During 15 years of growth, the vast majority of roots will grow in a “mesh” 12 to 18 inches just below the lawn. The six irrigated plants planted under the canopy will help somewhat but not enough. Removal of tree roots also reduces generally speaking, most trees can lose as much as 50% of their roots and still recover provided they get adequate amounts of water.

            My hunch is your mesquite will start dropping leaves at the onset of hot weather and you will see limb death in the canopy. The roots will try to reestablish themselves wherever they can find water but the canopy will die back because of root loss and inadequate amounts of water.

Tree dieback after converting from lawn to desert or rock landscape.

            What should you do? During this hot weather you should put a hose out there and irrigate the rock beneath the tree about once a week during hot weather. This is a stopgap measure.

            You might consider installing a “bubbler and basin” around the tree in the future to provide more water. Use an irrigation valve previously for the lawn for the water source to bubblers. An irrigation bubbler is installed 2 feet from the trunk. If this basin is quite large, two bubblers located in this basin might be needed to fill it. Each time you irrigate, fill the basin.

Mesquite blown over because shallow rooted due to lawn and flower bed

            It is important that the basin constructed is level and wide enough to lie on top of about half of the area under the canopy of the tree. A level basin, or berm, is built around the trunk approximately 3 to 4 inches high of the tree with the trunk at its center.

            The bubbler is a type of emitter that pushes out usually 1 to 2 gallons a minute. Drip emitters emit gallons in hours, not minutes, so this is a large amount of water applied in one spot in a very short. Of time. This is why the basin or berm is needed.

            If the tree is on a slope, then install the basin around the trees so that it is level. The water from the bubbler must flood the basin and be contained by the basin for it to work well. This may take 10 to 15 minutes with bubblers and anywhere from 20 to 30 gallons every time the tree is watered.

            In midsummer when it's hot this, watering might be once a week to every 10 days or so for desert trees like mesquite. Adjusting how often you water and how much is applied each time will determine how fast the tree grows and how dense the canopy is.

            If you begin to irrigate less often, but apply more water each time, you will slowly encourage the roots of desert trees like mesquite to grow deeper.

Don't Bet on Good Fruit from Rootstock Suckers

Q. I had an old peach tree of about 30 years die. We cut it down and had it removed. Last year several suckers sprouted from below the ground. They have different leaves so I know it is not peach. What are they? Should I leave them alone and allow them to grow?

A. Having a 30 year old peach tree is quite an accomplishment! They are normally a short-lived tree as far as fruit trees go. Peach is hit very hard by borers and may start to decline around 12 to 15 years of age. A 20 year old tree is really getting up there in age.

Rootstock on apricot

            When you purchase a peach tree from a nursery it is grafted (budded) onto a different tree called the rootstock. Basically, there are two different trees joined together; one is grown for its fruit and the other is grown for its roots.

            Frequently, the tree selected for its roots does not produce particularly good fruit. That is not the reason it was selected. It was selected because its roots had some particular quality that was desirable for the entire tree.

            Remove these suckers from the base of the tree. They will grow but the fruit produced will be low quality compared to the peaches that you enjoyed for so many years.

            

Select the Right Plants to Grow With Palms

Q.  I have had this palm for 10 years. Every time I add additional water with a hose or bucket I lose more fronds. Every year I cut higher on the palm to get rid of dead fronds. I drove a metal stake down 18 inches but did not pick up any visible moisture in 3 different places.  Any ideas on how I can go about this from a more scientific method?

Canary Island date palm with aptenia planted at its base

A. I did not see a whole lot wrong with your palm in the picture you sent to me. It is pretty normal for the fronds to begin to brown out and start to die once they drop below horizontal.

            In our climate it is also pretty common to have some tip burn on the leaves along the fronds, particularly as they get older and drop close or below horizontal.

            I did notice you have Aptenia, hearts and flowers, growing at the base of the palm. This plant is not complementary to a palm that has deeper roots. Aptenia has shallow roots so it is watered frequently with a small amount of water. Palms must be watered more deeply and less often.

            If you are going to plant something at the base of a palm, plant something with deeper roots that has a similar watering requirement. Replant at the base of the palm with something more deep-rooted that can give you some color.

            Select a woody perennial that give you season-long color in that spot or an evergreen with a deep root and a similar requirement for water.

Hibiscus Grows Differently in the Desert

Q. My hibiscus plant, transplanted from a pot to my outdoor flower bed, is blooming like it should. But the leaves are not getting any bigger than 1 - 1½" long and ¾" wide. The new leaves also only get to that size. I water and fertilize if with Miracle Grow regularly, but that does not help. Any suggestions?

A. The appearance of plants will be different when grown in different climate zones. I am now on my farm in the Philippines where we have Roselle hibiscus (commonly called Red Zinger) growing. I checked the size of the leaves in response to your email. I normally don’t pay much attention to leaf size just flower production.

Roselle growing on our Family Farm in the Philippines

            The leaves of our Roselle vary in size from the narrowest at about 3 to 4 inches in length and about 2 inches wide to the largest being 6 to 8 inches long and 4 to 5 inches wide. The largest leaves are growing in partial shade. The smaller leaves are growing in full sun.

Tropical hibiscus growing in the Philippines in a tropical climate.

            Appearance can also be impacted by your management practices. Let's cover a few of these.

            Climate and microclimates. Plants grown under high light intensities have a different appearance than plants grown under lower light intensities. The principal differences are in leaf size, color and thickness.

            Leaves growing under higher light intensities, provided they are getting enough water and nutrients, will be dark green, smaller, thicker or tougher and develop a thick waxy coating on the leaf surface.

            The same plant growing under lower light intensities will have larger and thinner leaves with a waxy coating that is not as thick. If light intensities get extremely high then we will see leaf discoloration, yellowing or bronzing, on some plants because the light intensity is actually damaging the leaves.

Red hibiscus growing in rock mulch in Las Vegas

            If the same plant does not receive enough light then the plant will become “leggy” with large distances between the leaves and thin stems that will not support its own weight. The plant will become "floppy".

            Our job as a manager of this plant is to find a good location in our landscape that provides the right microclimate which provides enough light for flowering and an appearance close to what we expect.

            Because we are in a desert, Hibiscus will not look similar to those grown in semi tropical or tropical climates but we can approach that look if we are careful where we plant it.

            Soil. Organic matter such as compost mixed into the soil at the time of planting and applied annually to the soil surface surrounding the plant will encourage larger and healthier leaves. I have seen this numerous times on a number of plants particularly in parts of the plants that are shaded such as lower leaves.

Red hibiscus growing in rock mulch in Las Vegas showing signs of leaf drop, leaf yellowing and branch dieback.

            Fertilizer. Fertilizer will influence the kind of growth. We know that phosphorus fertilizers are very important for flowering, fruiting, root development and production of oils in plants. If not enough phosphorus is present it will impact these types of growth.

            We do not need to apply phosphorus to a soil very often unless it is extremely sandy or growing in hydroponics.

            Nitrogen is different. Nitrogen is important for developing dark green color in leaves and stems and for "pushing" new growth. It is important in producing good leaf size and in the number of leaves and supporting stems produced.

            Nitrogen in soil available to plants also dissolves easily in water. Nitrogen is easily does not dissolve in water easily and is slowly released to plants.

            In your case you want to make sure that nitrogen is applied regularly through the growing season to maintain dark green color and "push" new growth. Combined with moderate amounts of shade, nitrogen will encourage more leaves and larger leaves.

            What should you do? Understand that if your hibiscus is in a very hot, bright location that this location will limit the plants ability to produce larger leaves. Moderate amounts of shade will encourage larger leaf development, particularly in a microclimate that gets morning sun but afternoon shade.

            Apply a 1 inch layer of compost and scratch it into the soil surrounding the plant as much as you can. When you’re done doing this, apply another 1 inch of compost to the soil surface and thoroughly wet the soil deeply. Apply a 1 inch layer of compost to the soil surface every year.

            Apply high nitrogen fertilizer at the beginning of the growing season. Apply a high phosphorus fertilizer after it is finished blooming. If you apply fertilizers at other times of the year, apply liquid fertilizers to the leaves.

            Do not apply any nitrogen fertilizers to the soil after August 1 if you are concerned about winter freezing damage. 

Texas Rangers Can Be Pruned Shorter

Q. Can I trim large Rangers so they are not so tall?

A. Yes you can and you can do it to this plant any time after the major bloom time or this winter. Texas Ranger can handle two different methods of pruning and one of those types will allow you to adjust the size of the plant more than the other method. Texas Ranger can be pruned into a hedge using a hedge shears or pruned into a single shrub.

Texas Ranger showing branches located at the base where pruning cuts can be made.

When any plant is getting too large the same general method of pruning is used to make it smaller. Some plants can rebound after severe pruning (like oleander) and others should be pruned with a more delicate touch.

To make it smaller.....First, identify one branch in the canopy which is too tall. With your eyes and hands follow this branch downward to a location where it joins another branch which is smaller. This location will be a "crotch" or "Y" where two branches are joined together.Make sure the remaining branch is growing in a favorable direction.

You will remove the taller branch by cutting just above crotch with a pruning shears that has been sharpened and sanitized. Make the cut so that the larger branch is removed and there is no remnant of that branch remaining.. The cut should be smooth with no remnant of a stump remaining. Find other branches that are to long or tall and cut them back using the same method. Vary the height of this cut above ground so that all the cuts are not at the same height.

In some cases, you may have to follow a branch a long distance close to the soil to find a favorable place to make a cut. You can remove branches at any of these locations.

If this is an older, large branch that is removed, it may leave a hole in the canopy. These holes will eventually fill with new growth from branches surrounding the hole. It will take a season for these holes to fill again so cut early enough in the season so the holes fill before winter. 

A much more dramatic but sometimes necessary method of pruning older plants is called renewal pruning. Here the shrub is cut nearly to the ground with new growth that will sucker from the cut stems.

The best time to make these pruning cuts are at the tail end of winter or very early spring before new growth starts.

Starting a Fall Vegetable Garden

Q. Could you help me get a fall garden going? Please send me a list of crops that grow in Las Vegas. I live in the northwest area off of Ann Road and Jones in Las Vegas

A. I posted a calendar for planting in the fall on my blog. Download a copy there but I will give you a rundown of the crops which are normally started this time of year in the eastern Mojave Desert.

            First, some background. There are two planting times each year. Plant cool season vegetables and herbs that withstand frost and cold during the late summer, fall, winter and spring months. Plant the warm season, winter-tender vegetables and herbs when danger of frost has passed and into the mid-summer months. Warm season crops die or perform poorly during cold or freezing weather.

            Even though it’s still hot now, this is the time of year to plant several fall and winter crops. Notice that I said many, not all. Exact planting dates vary with soil and air temperatures, the time plants require before they are ready to harvest as well as the quality of the end product.

            Cool season crops that require 60 or more days before harvesting will be just fine if planted now. It is too early to plant crops like radishes which are ready to harvest in 30 days.            

            Exact planting dates vary with your garden microclimate. Gardens located in warm microclimates have different planting dates from those gardens in cooler microclimates. If you are lucky enough to have a landscape with more than one microclimate, you can stagger your planting dates so that the same crops mature a few days or even a week or two apart.

            Plant gardens that face West or South later in the fall but earlier in the spring. Gardens facing east or north are planted in the reverse order.

            The following vegetables can be planted during September from seed or seed pieces for fall, winter and spring harvest: beets, broccoli, carrots, collards, endive, Irish potatoes, kale, kohlrabi, lettuce, peas, rutabagas, spinach and Swiss chard.

            The following could be planted as small transplants: broccoli, Brussels sprouts, cauliflower, cabbage, celery and Chinese cabbage. If temperatures are unusually hot, delay putting in transplants until weather cools off a bit.

            Mulch the soil to keep the seeds and roots of transplants moist and cool.

Identifying Their Damage and Controlling Borers

Q. I am having a problem with a bug infesting my trees. I haven't identified the pest but I wanted to first ask how did this infestation happen or if it's common in the Vegas Valley and second how is the cycle of reproduction of this bug?

Flat headed borer taken from tree

A. Thanks for sending the pictures. You have taken the larva or “worms” of a beetle from this tree. These larva or worms are called borers. You can notice the flattened head of this worm so it is commonly called a flat-headed borer.

I think it is either the Flatheaded Apple Tree Borer or Pacific Flat Headed Borer. I have been following this insect and its damage for many years in this valley. The adult of this “worm” is a beetle about ½ inch long.

Borer damage on Apple when first seen

The adult female beetle flies around searching for a mate so that it can lay its eggs. It finds a male by “smelling” the male’s pheromone it releases. Most likely this happens any time from about April through August. Once the female mates and prepares to lay eggs, she searches for suitable woody plants that are injured or unhealthy.

Extensive borer damage to Locust

This insect is part of an “ecological recycling cycle” helping plants that are on the decline continue in a downward spiral toward death. However, I have found this insect in trees that appear to be very healthy as well. The female laden with fertilized eggs searches for suitable plants through her sense of “smell”. One of the “smells” she identifies is damage of plants from sunburn.

Discoloration and canker to scaffold limb because of sunburn

High light intensity of our desert sun shining directly on the bark of trees that are thin and don’t provide much insulation become damaged and frequently die in the damaged area. Death in localized areas of the branches and trunk of woody plants leaves behind a “canker” in the surface.

Sunburn damage to Japanese blueberry

The smells and aromas of damaged plants attract the egg-laying of flat headed borers. She lays her eggs in the general vicinity of the damage but on top of healthy tissue. The very tiny worm or larva “hatches” from this egg and tunnels inside the plant just under the bark.

Borer damage to flowering plum

The wood just under the bark is laden with wet, sugary juices from the plant which the flatheaded borer feeds upon. As this flat headed borer feeds, it inches slowly forward just under the bark making a convoluted tunnel. At the beginning of this tunnel is the flattened head and it leaves a trail of sawdust and feces behind it as it feeds, moves and creates the tunnel. I can sometimes push on the bark covering the surface of these tunnels and feel a difference in the “hardness” of the stem.

Borer feeding under the bark inside peach tree limb

This borer matures (pupates or turn into an adult) inside the tree, exits the tree as a winged adult and searches for a mate to repeat the lifecycle. Sometimes, if it is late in the season, this borer will tunnel into the center of a limb to survive the winter and exit as an adult the following spring.

Borer feeding just under the bark of peach tree limb

Borers attack dozens of different trees and shrubs, many in the Rose family. This includes many of our fruit trees, landscape plants in the Rose family like Pyracantha and flowering plum and numerous others as well.

What to do?

Dig it out. Using a sharp and sanitized knife and laying it almost parallel with the branch, I will cut away the surface of the branch to expose the tunneling. I will remove all of the surface bark where there is damage. I will clean the surface bark all away until I have nothing but fresh wood remaining. In this way, I expose the tunneling and the source of protection for the boring insect. This exposes the hiding place to predators of this soft bodied “worm”.

Borer control using a sharp, sanitized knife

Prune it out. If the damage is more than 50% of the branch, I will remove the branch. If removing the branch seems excessive, I will not remove it and give it a chance to heal.

Using insecticide. In a last ditch effort I will use is a soil applied systemic insecticide. I never use these on fruit bearing trees but on ornamentals only. I will use these on non-flowering ornamentals because it is suspected that this systemic may impact bees visiting the flowers. If the tree produces flowers, I time the application of the insecticide just after the time of flowering.

One of the insecticides containing imidicloprid systemic for borer control

Whitewash to prevent. Whitewashing the upper surfaces of limbs, scaffold limbs and the trunk reduces sunburn which should also reduce problems from borers. I make the whitewash by mixing white latex paint 1:1 with water. You can also buy commercial whitewash. In the old days, it was made from lime.

Whitewashing fruit trees in the winter to help prevent sunburn

Pyracantha Does Not like Rock Mulch

Q. I have a hedge of pyracantha on the northeast corner of my property. It is 16 years old.  It grows underneath three large pine trees.  It does not get much sun. The soil, if you can call it that, is mostly just rocks. The plant is thinning and getting bare in the center. The top is still fairly green. The amount of berries in the winter has been decreasing. I dug around the roots as much as I could and amended the soil with Paydirt. I added about a cup of sulpher and some bone meal to the amended soil. I plan to add fertilizer in a couple of weeks. What more would you suggest?  By the way, there is very little yellow on the leaves.

A. Pyracantha is in the Rose family and so it likes soils that are similar to fruit trees in the Rose family. This includes apples, pears, peaches, apricots and the like. It is also susceptible to some of the same problems as fruit trees in that family. It isn’t terribly fond of desert landscapes and rock mulch.

Dwarf pyracantha in winter hedge sheared

Without seeing it I am guessing it is a combination of light as you mentioned, lack of soil improvement, perhaps irrigation, maybe improper pruning and borer problems. Pyracantha needs a lot of sun but it is thin-barked so it sunburns easily if it’s canopy is open. Sunburn leads to borer problems. It is not a desert plant so it likes improved soils and wood mulches. It would like surface mulches made of wood that can decompose. Rock mulch will mineralize the soil over time and it does not like this.

Pyracantha fruit in winter. Pyracantha or Firethorn is in the Rose family.

Pruning is a little tricky but should result in shading any exposed trunk or major branches. From your description it sounds like it has been a hedge pruned; pruned with a hedge shears not pruners. It hedges nicely but I don't recommend this unless you plant it as a hedge. As far as borers, you would see the trunk or major limbs with bark coming off and some darkened areas because of sunburn. Borers can be active for a couple of years and cause no obvious visual damage. There is an insecticide you can apply to the soil that gives the plant season-long control of borers if it is a problem.

Pyracantha in bloom in the spring

So what to do? Check the irrigation and make sure it's getting enough water or increase the amount it gets. I would not increase how often but the amount it receives each time. Pull rocks away from the plant and put down 3 to 4 inches of compost and wood mulch. When pruning, be very careful you don’t open the canopy up too much which might allow sun burning the trunk and limbs. Fertilize once a year in the spring with a fertilizer formulated for flowering woody plants. You can substitute a rose fertilizer which will work. Apply a soil insecticide as soon as you start to see new growth. I hope this helps.

For more information please visit the following

http://xtremehorticulture.blogspot.com/2015/01/care-and-pruning-of-pyracantha-and.html

http://xtremehorticulture.blogspot.com/2014/12/pyracantha-good-choice-for-moderate.html