Large Percentage of Pomegranate Fruit Comes from Older, Larger Wood

Q. I need some help.  I planted a pomegranate tree about three years ago. The tree looks great and there are always lots of fruit. The problem is that by the time the fruit gets up to about 2" in size they are splitting open.  Can't figure out the reason and I am yet to harvest a good pomegranate.  It gets full sunshine in summer and water 3-4 times a week. Any suggestions?

A. Are the arils (pulp) sweet? Maybe it is ready to harvest.

            First of all, the fruit should be larger than that. The fruit should get larger as it gets older and the tree is pruned correctly. A high percentage of small fruit is produced on smaller branches.  The number of large fruit is more as the tree gets larger. A higher percentage of larger fruit will come from the larger branches. That's the reason for getting rid of the much smaller suckers. Get rid of the suckers at the bottom of the tree and force production on to about 5 or 6 main limbs that you keep. The best and larger fruit are produced on older wood. Small fruit are produced on young and smaller wood. I think the reason why some California growers prune toward only one large central trunk is that the fruit collected from it gets larger earlier. 

Pomegranate pruned into a tree shape instead of a bush.

            If the fruit is green when it splits, the same is true. The tree was not getting enough water as the fruit was getting larger. The fruit starts to become red, or red or white, or red and white when it starts into its last ripening phase.

Yellow pomegranate brought to me in Tajikistan.

            Fruit splitting is oftentimes a harvesting problem. Taste the seeds inside (called the arils) and see if they are sweet or ‘as expected”. There is a wide variation in flavor so don’t be surprised if the fruit taste is “puckery”. If the arils are sweet or “as expected”, it might be ready to harvest. Pomegranates are ready to harvest, depending on the variety, from September (‘Utah Sweet’) until early December (‘Wonderful’). The fruit should not crack unless they are past their harvest time.

Young fruit still green and developing. It is several weeks away from harvest and sweet.

            If the fruit are splitting before they are ready to harvest (not sweet yet but getting there) then it is a watering issue. Just like melons, as the rind sets up for harvest (sugars are accumulating) watering becomes critical. Watering when the rind gets hard (and it doesn’t need it) will split the fruit.

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Pomegranate rind split and ready for harvest. Probably 'Wonderful'.

Mastic Tree Problems

Q. Can you tell from the attached pictures what might be happening to our mastic tree?

Mastic tree.

A. My guess is that the new growth is filling a “hole” made when the plant became a shrub. Mastic is a Mediterranean tree or shrub that grows slowly and naturally as a bush, to about 20 tall by 20 feet width. It requires, at the least, annual pruning when it is young to shape it into a single or multitrunked tree. It is best used as a background tree or shrub and not a smaller version of the larger Chinese pistache. It is not as pretty. It lacks fall color, tends to be shrubby, and smaller, but does have red ornamental nuts when they are young and before they ripen around August.

            If this plant were mine and I wanted a small tree instead of being shrubby, as it tends to be, I would start to prune it in the winter or late fall months. Make a decision whether you want it as a single or multi trunk tree and make the appropriate cuts.  I would expose the trunk or trunks of this tree up to my knees by starting at the bottom of the tree. I would eliminate any growth below my knees and keep any upright growth. If I saw any suckers at the base, I would eliminate them. While it’s young, I would eliminate any growth growing downward or horizontal. I would concentrate most of my pruning efforts on keeping any upright growth to make it look like a tree and give it some height.

            Water it like you would an olive tree. It is mesic in its water use. It will attract the leaf footed plant bug. Shearing this tree with hedge trimmer is a mistake. Fertilize this tree once or maybe twice lightly with a standard landscape fertilizer such as 16-16-16.

Sap Coming from Small Fruit Trees Usually Borers

Q. I have some newly planted peach and nectarine trees with sap coming from them. They don’t look healthy.

Sap oozing from newly planted fruit trees nearly always borers.

A. Borers are most likely the problem. On small, newly planted fruit trees it doesn’t take many borers to kill the trees. They usually “attack” the south or west sides of a trunk or the limb of a tree. That’s where there is sun damage. Painting these trunks and limbs with white latex paint lowers the surface temperature about 4 or 5 degrees. It may be enough in some cases. But shade is better.

Borers will usually start to damage the hot side of a tree, either west or south.

            The sun plays a role also. Direct sunlight on the trunk of a thin barked fruit tree can be a problem. The “smell” of sunburned and dying or dead limbs and trunks attracts female borers that are looking to lay their eggs, scientists believe. When limbs and trunks of newly planted fruit trees have sun damage, then borers are more likely to be found.

This is a locust tree. Borers "smell" or find their way to the sun damaged areas of any tree. Here the top of the branches have been damaged by the sun. The bottom of branches out of sunlight are undamaged.

            What to do? 

Shade the young tree from Western and Southerly direct sunlight. Paint the trunk with diluted white latex paint. As a last ditch effort, drench the soil around the tree after it flowers (if possible) with a borer systemic insecticide and don’t eat the fruit for at least 12 months after the application.

Which came first? Here sun damage eventually led to borer damage.

If Fruit Trees are Planted Correctly They Can Take the Heat

 Dig the hole three times WIDER than needed. Plant in a wet hole. Amend or mix that soil or bring in different soil.

The planting hole is dug three times wider than you need it.

Amend or mix the soil with about 20 to 30% of a very good compost.

Mix in a good compost when planting.

Stake all fruit trees. Make sure the trunk cant move when you are finished.

Stake fruit trees, all of them, so the trunk can't move.

Protect the fruit trees from rabbits with chicken wire for the first three to four years if you live near a golf course or an open desert.

Put at least two inches of mulch (wood chips that rot) on top of the soil. Three inches is better. Keep it 6 to 12 inches away from the trunk until the tree is six years old.

These are wood chips from whole entire trees, not bags of wood bark.

Water every other day or every third day, wide and deep.

Fruit Trees Like Hot Weather if Prepared for It

Q. Now that it has gotten hot, my fruit trees (some new, some established) don’t look so good.

When fruit trees are fist planted, if they are not planted right they will look a bit rough. Their looks will improve with time if these deficiencies are corrected. If their size (and increased water use) and soil improvement is accounted for when watering they will look better and better.

A. When fruit trees are first planted, they may look good. That is because they are watered correctly for the first three or four years. After that fruit trees get bigger, and need more water applied wider and to the same depth. This means more water! Don’t change how often they are watered. When they are watered, they need to be watered to the same depth, to a wider area (which means more water) and with an increasing amount of water each time they are watered. This is because they are bigger, and water should be applied to a wider area.

When fruit trees are first planted (when the weather is cooler) they need water every other day, improved soil and soil put in a flat and level moat around the tree to capture it.

            What I find to be effective is to apply water to the area under a mature fruit tree (seven years in the ground and longer) that is about six to seven feet wide. Much of the area watered depends on the soil you have but most soils are (even though they are hard when dry) a sandy loam when irrigated. I prune fruit trees (in the winter) at seven feet and let them grow during the year to close to 8 or 9 feet tall, not their full size. This pruning allows for ladder-less fruit harvesting.

When the fruit tree is three or four years in the ground the tree is pruned to establish the major fruit bearing limbs

            To do this I water the fruit trees to about 18-24 inches deep in the soil. The area I want to apply water is about half the area under the fruit trees. This usually requires about 8 drip emitters (or two concentric rings of drip tubing with emitters placed 18 inches apart) when the fruit trees have been in the ground 5 to 6 years. The rings are spaced18 inches apart, too! The fruit trees are planted about ten feet apart in all directions. I prune them so they fit into this area, and you can walk around them to harvest, fertilize, and prune.

Limbs are only removed at the bottom if they touch the ground. Otherwise picking fruit starts at the lowest limb!!!!

            Figs are good to have in the orchard because, in my experience, they grow but will not fruit if they come up short on water. Fruit is the first to go, not growth. If you have fruit on your fig trees in July and August, then the other trees are getting the right amount of water too. Figs are a “water indicator” fruit tree for me.

Fig trees, as all fruit trees, are big solar collectors. If you cant reach the fruit it is wasted. If the fruit is too low it is wasted. If the fruit is too close together it is wasted.

Low Water Use Plants Need Water in the Desert

Q. Over a year ago our city planned a new extension to a community Park and put in a dirt trail surrounded by “native plants”. They dug wells and put in an assortment of plants and trees with no water source. The first month they used a fire hose from the hydrant to water the plants. Since then, nothing. I counted over 185 dead plants this morning. My question to you is there certain plants for that zone or location that will be able to survive without any water?

Cleveland sage is best planted on the east and north sides of a building. It comes from the Baja and coastal California where it grows best in a Mediterranean climate.  Water to get it established and then not more often than about every two or three weeks.

A. Not really, no. Even cacti occasionally need water to get established and grow after planting. Cold hardy desert plants are best planted in the fall; winter tender plants in the spring. In very dry summers, desert plants will need supplemental water once a month or more during the summer to look good and survive. Cities and homeowners are not Mother Nature. Even so-called desert plants need water occasionally (and usually some soil improvement) periodically/regularly/deeply to look their best. Homeowners won’t tolerate plants that look bad.

Opuntia, or bunny ears cactus, are native to all over the desert southwest including the Mojave desert. To get growth water them about every three weeks in the summer.

            For each plant that makes it in the desert after a rain, thousands of plants don’t. The advantage of desert plants is their ability to survive periods of time without water. To think we can guess where plants will survive after planting is pure arrogance. Desert plants respond to water. They respond best when the water is applied to the same spot. They respond by growing.

Texas sage or ranger (the barometer plant) hates, hates, hates to be trimmed by a hedge shears unless its growing as a hedge. This is what happens. Water it about once every two or three weeks or when the leaves start to drop.

            Some, like Texas ranger (the barometer plant of the Chihuahuan desert) produce flowers on new growth after a rain. As these desert plants get drier, they first drop their leaves (if they have any). Even cacti will put on some new growth after a rain and may even flower!

Grape Bunch Disease Need Applications of Fungicides in the Spring

Q. I am a big fan of your RJ newspaper column, but I haven’t seen any answers about what’s happening to my grapes. Please advise. This the stuff isn’t on all my grapes. I have four plants and maybe 10-15% have this white stuff on certain bunches.

This is from the reader and I would call it a "bunch rot" a bunch disease that must be controlled in the spring, according to the fungicide label. Most homeowners use a "copper based fungicide for control.

A. It’s a disease of the bunches; a “bunch disease”. I thought this might happen mostly because of our wet spring. Bayer tells us, when treating for grape bunch diseases, that about half of the improvement is due to better air circulation and the other half using a copper-based fungicide. They are right! Collectively, both downy and powdery mildew are called “bunch diseases”. The fungicide must be applied right after a rain or during high humidity days just after it flowers. Grapes flower in mid March in Las Vegas.

One of the bunch diseases later in the summer (about May) from about three or four years prior. To late for the first application of most fungicides but give it a try.

            This looks like one of the grape diseases, probably grape downy mildew. Try removing bunches and leaves so that you have one bunch every foot. If it is tight with leaves, remove some of the leaves as well to improve air circulation. Don’t remove too many leaves so that you get direct sunlight on the grapes or limbs. You want to improve the air circulation around the bunches and the berries but without putting the bunches (and limbs) in direct strong sunlight for any length of time in the desert.

One of the grape bunch diseases from a few years ago in Las Vegas.

            You can apply a spray mixture of a copper-based fungicide according to the label. Liqui-Cop and Bordeaux sprays come to mind, but any copper-based fungicide (a fungicide that includes copper in the ingredients) should work. You may have to repeat the application. Read the label. 

Warning. Grapes must be on the label of a fungicide because of testing and recommendations concerning the rate of application.

One of the many copper-based fungicides. Check the label to make sure your crop and rates are mentioned.

            Remember fungicides help prevent plant diseases but do not “cure” the plant of a particular disease. You are spraying early to prevent the spread of a bunch disease. There is some evidence that Neem oil has given some protection, but copper-based fungicides are better.

Grape leaf removal around grape bunches to improve the air circulation.

            You may be too late with a spray of any kind, but it is worth a try. Do it very soon and follow label directions for controlling these “bunch diseases” on grapes. Next time apply your favorite spray earlier in the season, right after rain or during high humidity, to prevent the spread of “bunch diseases”.

Wittwer Vegetable Primer Available

Q. I received the Wittwer vegetable “bible” but I must admit, I'm a little confused by the title, as It seems to be pertaining to Moapa and Virgin Valleys and not the Las Vegas Valley.  As longtime residents of the Las Vegas Valley, don't those valleys have a different climate than the Las Vegas Valley?

Dr. Sylvan Wittwer's vegetable garden in Logandale, Nevada, eastern Clark County in southern Nevada. Vegetable growing conditions are similar to Las Vegas.

A. Yes, they do. It is slightly different, a bit warmer to be exact. The climates between the two valleys are very similar. Both valleys are in the Eastern Mojave Desert. It’s hard to find information from a source like Dr. Sylvan Wittwer for the Las Vegas Valley.

Dr. Sylvan Wittwer was the past extension vegetable specialist for Michigan State University but originally from Hurricane, in southern Utah in Washington County.

            Dr. Wittwer was the retired Vegetable Specialist from Michigan State University when he moved to our eastern Mojave Desert climate. He grew vegetables in this climate for eight years before he moved back to Utah. It’s difficult to find reliable information in the Las Vegas Valley from such a notable source.

If you want, contact me at xtremehorticulture@gmail.com and I will email you the entire pdf copy.

Elm Leaf Beetle on Siberian Elm, not a Chinese Elm

Q. Looks like elm leaf beetle or leaf miner damage in the picture I sent. What to do? Let the tree flush a new set of leaves after the larval feeding frenzy? These are trees cared for by volunteers and found in Spring Mountain Park near Blue Diamond. I would rather have the volunteers not use any systemics. Any thoughts?

This is elm leaf beetle damage to Siberian elm. To my knowledge the elm leaf beetle only attacks Siberian elm. Siberian elm is different from Chinese elm.

A. That’s elm leaf beetle (ELB) damage on Siberian elm leaves. We used to see a lot of it when there were more Siberian elms in our community. If you can catch them in the larval stage, they are easy to control by spraying the leaves with any type of insecticide. Any insecticide works including soap and water and salt sprays. You just need to kill them.

That's elm leaf beetle damage taken from a slide over fifty years ago in Colorado.

            The problem is the act of spraying which means specialized equipment because the trees can grow 40+ feet tall. Soap and water sprays kill on contact. They don't have any residual, so you must spray the leaves until the level of control you want is achieved. Otherwise, you must use a systemic insecticide as a soil drench or have it absorbed through the tree trunk.

Larvae of elm leaf beetle adults (don't confuse them with adult cucumber beetles) taken from a slide over fifty years ago. They are ephemeral, meaning they last only a few weeks and they are gone.

This is a nearly mature form of Chinese elm, maybe evergreen elm. Notice how tall Chinese elm can grow. Don't confuse them with Siberian elm which is a trash tree.

            I just ignore them and tell people not to plant Siberian elm when I see it. Recovery of this tree from single feeding by ELB is not a problem. I have only seen ELB eat the surface of Siberian elm leaves, not any of Chinese elm types including lacebark elm. Plus, ELB has only one generation each year while other insects, like the great leaf skeletonizer, is more destructive and mates multiple times each year.

            I consider Siberian elm a “trash” tree and ranks about 2 out of 10 in desirability. Chinese elm, on the other hand, is a much better tree and I would give it an 8 or 9 out of ten. By the way, Siberian elm is no longer sold as a landscape tree. No great loss.

Siberian elm removed with a telehandler...aka forklift... at Aherns

Parts of Drip Irrigation System

Q. When installing drip irrigation, what irrigation parts do I need?

Drip irrigation must have a filter and a means to regulate the pressure, a pressure regulator. https://www.digcorp.com/wp-content/uploads/digcorp/DripZone-1.pdf accessed on August 1, 2023.

A. Make sure there is some sort of filtration, a pressure regulator to lower water pressure, and a way to “flush” the irrigation lines of debris, algae, and bacteria. Many people forget the flush part because they are used to using city water which is very clean. Every drip irrigation system needs these parts. It makes no difference if the filter or pressure regulator is first but drip systems need lower pressure. It works either way (pressure regulator first then filter or vice versa) but the arrows of water flow are important.

A flush valve can be as simple as a ball valve connected to the irrigation circuit but it must be buried so it can be found and used. 
https://www.landfx.com/docs/item/202-land-f-x-drip-irrigation-design-and-graphic-conventions.html accessed on August 1, 2023.

            The flush valve (oftentimes just a ball valve or on and off valve) is placed farthest away from where water first enters the “system” and hidden from site but easily found and used. The “flushing operation” involves cleaning the filters as well as cleaning the lines of algae and bacteria with the flush valve.

            Cant say how often to flush the lines but drip irrigation MUST have clean water to operate. Well water is a "dirtier" water than city water. Wells pick up sand and other sediment that needs regular and periodic flushing. Once you get into a "rhythm" for how often to flush (every other time you water or every fifth time you water??) it doesn't change much. Just plan on it when you use well water.

Hunter screen filter and pressure regulator in a bag.

            Lower the water pressure with a pressure regulator. Water pressure from a municipality fluctuates depending on how close you are to the municipalities water pump or reservoir. A plastic pressure regulator helps lower the water pressure into the “normal range” to operate drip irrigation. The pressure of water from wells may vary. For most homeowners, the water pressure range for smaller drip systems is approximately 25 to 30 psi. For larger drip irrigation operations (half acre and above), water pressure of drip systems may need to be more than this.

All PE tubing specifies its operating pressure and other important information such as emitter distance, size of the emitters, etc.

            Water used in drip irrigation needs to be particle free. Clean it before it comes in the drip lines. Drip irrigation relies on small holes that can plug, to deliver water. Clean water requires filtration. Even though water from municipalities has been filtered, filtration is still needed for drip irrigation. Most commonly and inexpensively, screen filters (screens are 120 -130 “mesh”, which means 120 to 130 holes per each square inch) are used. The filter is added, usually after an irrigation valve.

Pressure regulators must be used to protect the drip tubing from operating at too high of a pressure. If incoming pressure is to great or fluctuates, a more substantial pressure regulator (such as brass or more permanent type) should be used. Incoming water pressure should not exceed the PE or fitting operating pressure. Rainbird pressure regulators https://www.evergreen-irrigation.co.uk/product/rain-bird-water-pressure-regulator/

            Regular flushing cleans the lines of debris, algae and bacteria. It is important to flush the lines every time repairs are made as well as regularly. Part of the “flushing operation” requires a separate “flush valve”. This is particularly true if using a fertilizer injector.

            When designing drip irrigation, I prefer the “closed loop” type of irrigation system design. That's where there is a header and footer that "close the loop". Closed loops minimize the number of places where you have to flush and “evens-out” the water pressure of the system. It costs a bit more to install but the benefits are worth it in my opinion.

Plant Roots Prefer Water and Nutrients Applied to the Same Place

Q. I have read that plants grow better with water delivered to their roots, at the same spot, over and over again. Is this true?

Eggplant growing with drip irrigation in a raised bed without sidewalls.

A. Yes, it’s true but you probably won’t notice the difference. Why? Unless you compare plants growing with water applied to the same spot, over and over, with plants watered at different places you wont see much difference. 

            Plant roots get used to the amount of water and air when water is delivered to the same spots and depth, over and over. That is one reason why drip irrigation, along with the proper spacing of emitters, is so successful as long as the plant “wets its roots” to the appropriate depth each time. Watering with a hose will not as consistent.

            Water should wet the roots to the same depth every time. Small shrubs need to wet their roots to a depth of 12 to 18 inches, medium sized trees and shrubs 18 to 24 inches deep, and tall trees or shrubs should have wetted roots to a depth of 36 inches deep. This water should be applied to at least half the area under the plant’s canopy. Obviously then large plants need more water applied to them, and this water applied to a larger area, than the smaller plants.

Yellowing Container Cycad in the Summer

Q. My cycad (sago palm) is yellow. I had read that it needs magnesium. What do you recommend?

Sago palm (cycad) yellowing in container.

A. Make sure the soil in your container drains and the plant is not watered too often. Repot or replant the sago palm when temperatures are cooler. Either wait or take it inside your house where it’s cooler when you replant and the plant reacclimates to the repotting in a week or so. Use a soil moisture meter when watering to make sure it’s not watered too often. Sometimes watering too often and poor container drainage of the soil can cause plant yellowing.

Repotting sago palm (cycad) and watering as it gets hot helps cycad stay green.

            Judging from your picture, your plant yellowing may be a fertilizer (plant nutrient) or watering/drainage problem. Iron shortages in plants are notorious for yellow foliage. Try applying an iron chelate to the soil when growth is first starting. Applying iron to the soil works if the plant is still growing. Once the plant stops growing then iron applications to the soil don’t work very well.

There can be two reasons why nutrient deficiencies appear in soils of any kind; a shortage of a nutrient (you are suggesting a shortage of magnesium and you could be right) or the pH of the soil or its level of alkalinity. The reason I focus on iron so much is because a shortage of iron is very common to our soils and due to our tap water. Iron is probably the most common plant nutrient shortage due to our soil and tap water alkalinity. So try iron first. If that fails to "green the plant up" then try a different container soil (repot it with a different soil mix).

This chart shows you the shortage of different plant nutrients with alkalinity (soil or water pH). https://extension.wvu.edu/natural-resources/soil-water/soil-testing/soil-test-nutrient-needs accessed on August 1, 2023.

Putting sago palm in container in the correct landscape exposure can help.

            After around June or July 1, iron applications must be sprayed on the new leaves and stems. In some cases, multiple spray applications a week apart are needed during that time. Before new growth starts in early spring, apply this same iron chelate mixed into the soil. It’s much easier. If in doubt, use an iron chelate containing EDDHA. Search for it online if you can’t find it.

Magnesium deficiency, University of Florida, 

            Magnesium deficiency (which you suspected) is usually a speckling of leaves or fronds. It’s not usually yellowing. There is an abundance of magnesium in most of of our soils, but maybe not container soils. It is hit and miss. If you want to try magnesium (can be like whack-a-mole with plant nutrients), Epsom salts contain magnesium so apply 1 to 2 tablespoons of that mixed or the potting soil. Most plant nutrients won’t hurt the plant. Additions of boron is an exception so be very careful applying boron, chlorine or sodium. Higher levels of that can damage plants. (It is safer to repot with a different potting soil or, if that fails, put it in the ground.) After replanting, water the plant until water comes out of the bottom of the container. Even though sago palm or cycad is not a “palm”, lightly apply palm fertilizer to the soil once a year in the early spring.

Variable Output Drip Emitters

Q. I read somewhere not to use the type of drip emitters that you have to open to get water. What say you?

Two emitters are not enough to accurately provide water to a tree as it gets larger. If these emitters flood the area under a tree the water should be captured by a moat or ring of soil surrounding the tree about six feet in diameter. 

A. They are called variable output drip emitters. I don’t like what are called “variable output drip emitters” (the kind that releases a different amount of water depending on how much you “open” it using a dial). You don’t know how much these drip emitters are releasing because there is a loss of precision. Opening it varies the output of water from 0 gph (no water) to 10 gph (wide open). It depends on how much it’s opened, and it doesn’t tell you the amount of water it delivers. “Wide open” might be more than 10 gph for some manufacturers. For me it’s like playing “whack-a-mole” when variable output drip emitters are used. Using variable type drip emitters makes it difficult to tally how much water is used.

Variable flow or variable output drip emitters don't have much precision. You can open it or close it but how much you give a plant is anybody's guess.

The irrigation industry has started to color code drip emitters. If single drip emitter has a specific color, such as red, all of the emitters from that manufacturer are the same. If all the emitters are the color red (2 gph) for example than any drip emitter with a red color will release the water at the rate of 2 gallons per hour. Netafim.