Xtremehorticulture

Xtremehorticulture of the Desert

Plant What You Eat

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Q. My wife and I recently purchased a home in Las Vegas. It is on a little less than an acre and has access to well water. Currently on the property, it is mostly just dirt with a few pine trees. We want to plant an orchard with a lot of different fruit trees that will grow well, and we have seen a few of your articles in the RJ. In one of them, you suggested the questioner to email you for a list of recommended fruit trees for Las Vegas and we are hoping you could email that to us as well. A. First of all, I would not plant anything during this heat unless it is very early in the morning when its cooler. Even then its a problem at this time of year. This includes any of the fruit trees. Plant what you will eat. If like to eat peaches, then plant peaches. If you like apricots, then plant apricots. If you like to eat plums, then plant plums. Too many people plant Myers lemon (a citrus). What can you do when 200 pounds of “lemons” are ready during the three or four weeks of January or February? Your neighbors will see you coming with a bowl of lemons in February and not answer the door! We live where our winter weather can get cold at times (freezing), and warm at times (not freezing). There are fruit trees that survive the cold weather by dropping their leaves (we call these temperate fruit trees). Then there are subtropical fruit trees such as all the citruses. They prefer the non-winter temps but survive winter weather.  The average killing temperature during the winter of temperate fruit trees is about 15F. The average killing winter temperature of subtropical citrus is about 28F. Some temperate tree crops tolerate our winter cold temperatures better than others (apples, pears, for instance) and some do (pomegranate, figs, for instance). Citrus production is in Yuma Arizona, Riverside California, Galveston, Tx, and the southern half of Florida. In our climate, (in my opinion) growing citrus is “experimental”. The risk of losing citrus is high because of our winter temperatures. Temperate fruit trees are affected by the heat of summer. That is their “winter”. For this reason, I did not evaluate any subtropical “citrus” in this report.

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Persimmon Fruit Will “Sunburn” in the Desert

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Q. You are certainly correct about some of the persimmon fruit getting sunburned. I had to remove 15 persimmon fruit because of sun damage. One thing I have noticed is that some of the new growth from the main branches are aimed downward so I am hoping to eventually grow the tree closer to the ground so more fruit is in the shade. All the fruit is small. Hopefully, since this is the first crop, the situation will improve as the tree gets bigger.  A. You’re right, persimmon fruit does get a bit larger as the tree gets bigger, if it is “thinned” appropriately, and fertilized in the spring. Play around with it. It may be a bit late for your trees, but try planting persimmon fruit trees on the east side of your home so it gets afternoon shade. Hopefully, it will reduce the number of fruit that have sun damage. Tree fruit needs only about 6 to 8 hours of full sunlight. Morning sun is best for persimmon trees of all kinds. If fruit trees are planted too close together, they may get too much shade. Try growing the variety ‘Giant Fuyu’ if you want larger fruit when the tree is three to five years old. Your persimmon varieties do not have lower limbs to provide some shade for themselves and they are planted very close together. I like semi-dwarf fruit trees planted 8 to ten feet apart and no more than ten feet tall from pruning. If the persimmon tree is already planted in full sun, I have had luck producing fruit without sunburn as the trees get bigger together with appropriate pruning. The pruning I give them produces the shade the fruit needs to produce undamaged fruit. Before it flowers, but after new growth has begun, I will “tip prune” them. This means I will prune the new growth by about half as it is developing. In about one month of new growth (after pruning), new stems produce fruit on the top and bottom of this new growth. When I am thinning the flowers, I remove the top flowers in the hot sun. This gives the remaining bottom fruit the shade they need. Persimmon fruit grows on “current season wood”. Unlike most temperate fruit trees, it produces wood in the spring, then it flowers on this wood, and finally fruit is produced from the flowers. Never thin the flowers as you don’t know if it turns to fruit or not. Some fruit is not pollinated. Wait until you see small fruit developing, about one-half inch in diameter. Then thin. Another fruit tree that produces its fruit late (on current season wood) is pomegranate. The fruit gets damaged (discolored rind or worse) in full sun and both the tree and fruit benefit from afternoon shade when grown in the desert.

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Apricot Tree Dying in Mid Summer

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Q. My apricot tree is 15 years old. I have emitters around most of the canopy. I gave it fruit tree fertilizer in early spring. This spring it developed a lot of apricots then a few weeks later the leaves started turning brown and falling off. I fear my tree is dying. Any suggestions? A. This is the time of year we see borers finish their nasty work. This is not peach tree, or crown borer that gets into the soil as it does further north. These borers have been tunneling just under the bark, staying in the tree, and are “flatheaded borers”. It is possible that borers may have been a problem before your tree was 15 years old. When we see the tree dying it is often times later in the year (usually July or August) when it gets hot. Often times the tree has an exposed trunk facing west or south. The trunk gets hot, scorches or sunburns and the borers infest the tree where there is damage. Like I said, this borer infestation can happen over several years when it is older like yours. In young trees it can happen over one or two years. What to do? Look for borer damage of the tree trunk where it is exposed to direct sunlight. I would get borer control insecticide containing the active ingredient imidacloprid and treat it now. Make sure a soil drench is mentioned on the label. You can always look for borer damage after you apply the soil drench treatment. Normally this treatment is done earlier in the year before damage is obvious, around March. But it is worth the treatment now in hopes the tree will improve. Since the fruit has already been harvested (it finished flowering in February) the soil drench is straightforward. The tree may continue to get worse before it gets better, or the tree may die outright because the visual damage is so extensive. Your other option is to remove the tree and buy an apricot and plant it in the same hole. I would recommend any apricot on any dwarfing rootstock. Plant any of them in October when it is cooler. If it is borers, they are only in the tree and not the soil.

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Bird of Paradise Growth

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Q. I really want a red bird of paradise in our yard. I killed a new plant last year by over-watering. We have the typical irrigation of watering in the early morning and after 7pm. Other than size of the sprinkler heads we use I don’t know how to water my new plant. Can you help me? A. This plant died from watering it too often. It may not use a lot of water, but it needs to get watered more often than a desert provides or it will die. It, and its relatives, grow naturally throughout the tropics and subtropics where water is available ideally more often.             Secondly, the only plants that need daily watering in the summer are very shallow rooted lawns (ex. tall fescue), most annual vegetables (e.g. tomatoes, eggplant, peppers, etc.) and annual flowers like petunias and snapdragons. Generally, the larger the plant, the deeper its roots. Woody plants that grow to three feet tall have roots that can grow as much as 12 inches deep; woody plants up to 12 feet tall have roots that can grow as much as 18 inches deep, plants that are 25 feet tall have roots that can grow 24 inches deep, etc.             Water according to the 40-30-20-10 rule. If any sized root (12 inches to three feet) is divided into fourths, the top fourth consumes the most water, next is the second quarter, then the third, etc. When water use is calculated from dead plants, it is found that the top fourth uses about 40% of the water, the next quarter uses about 30%, then 20% and the last approaches 10%. If you want deeper roots, apply water all at once to root depth; let the first quarter use the water and don’t water again until the second quarter is being used. When you water this way, evaporative losses are minimized, and more water gets the roots to grow.             All woody plants (your red bird of paradise is a “woody plant”) need at least one day without any water during the summer. This type of watering allows roots to “breathe” and develops deeper root growth. It improves heat resistance. Ideally these plants should be watered when the soil is no longer moist but starting to dry when the probe is pushed 4 to 6 inches deep.

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Substitute an Insect Product and Eat the Fruit?

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Q. Tell me what you think about this product. Could we use it on a fruit tree to kill borers and eat fruit the same year? A. I am looking at the label you sent. I am looking at the active ingredients listed. The active ingredients tell me that I am applying “Imidacloprid at 1.47%”. The remaining 98.53% are “OTHER INGREDIENTS”. The active ingredient is a small percentage (in this case1.47%) of the total product (100%). This active ingredient still must be diluted with water at 1.5 teaspoons of this product per gallon of water in order to spray it or use it as a soil drench (8 to 30 ounces of this product for each gallon of water depending on the size of the fruit tree). This product gives one season long control of borers. However, after three weeks of application, whatever remains of this product in the fruit, is safe to eat according to the label. It is your call. I get worried when it “gives season long control” of borers but it is safe the fruit is same to eat after 21 days. I prefer telling people to throw the fruit out that remains on the tree for one season even though the label indirectly says the fruit is safe to eat. Follow the label if you want and eat the fruit after 21 days.

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Don’t Use Wood Shavings with Glue

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Q. My son has a lathe and does a lot of turning of bowls and other similar items. This creates a lot of wood dust. I was wondering if the wood dust can be used to fertilize or mulch the garden? I know you have said to use small chips for mulch. It seems to me that the dust should be good for something rather than throw this out. A. A variety of sized particles of wood is better for your soil, physically and chemically, than adding “sawdust” alone. As it decomposes it adds to the soil “organics” which can be good. It goes without saying that this is not plywood or particle board sawdust. This type of sawdust adds “glues” to your soil and is better off in a landfill. You can use it but be careful when using it. Adding sawdust to your soil can cause plants to become yellow from a lack of nitrogen as this sawdust decomposes. I would mix it with some high nitrogen fertilizer (high first number). Use a fertilizer high in nitrogen (the first number) such as a tomato or lawn fertilizer. Be careful of dumping large amounts of dust of any type on the soil surface in one location. It can alter the soil physically. This dumping can “suffocate” plant roots and change a soil’s physical property so that air exchange decreases. If there are various sizes of wood particles, then they are perfect (physically and chemically) to build up the organics of the soil as it decomposes. If it is “sawdust”, then it is no different, physically, from any dust. Sprinkle sawdust onto the soil, right through any surface mulch, a little at a time. Avoid dumping it in one spot. Spread it out! Distribute, sprinkle and incorporate this type of sawdust, along with a high nitrogen fertilizer, where it will get wet and rot faster.

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Heat and Plants

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Q. Will this heat damage plants? A. Most likely not. If the plants have been in the ground for a few years, then they are acclimated or have become accustomed to it. The problems come from those plants recently planted or planted during the heat. Flowering plants need six to eight hours of sunlight every day. Non flowering plants can get by with less. Your choice, when they are planted, is whether these plants should get morning sun (primarily east or north sides) or afternoon sun (south or west sides). If they are growing successfully in a location you’ve chosen for them, then don’t move them.

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Figs Are “Oasis” Plants

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Q. I have ‘Brown Turkey’ figs that are ten and twelve years old. This year the fruit is large, but as they are lightly purpling up, the skin has wrinkled, and the fruit is very dry within. Some were black, like smut, but mostly dry, and lumpy. A. Check the amount of water your figs are getting. Most figs should be watered twice a week right now. All fruit trees should not be short on water during its production of fruit. We are quickly approaching day/night temperatures (and wind) (mid June) that require watering figs three times a week. The higher temperatures demand more water for production to continue. Just don’t water any fruit trees more often than every other day. Many plant leaves close their stomates (most of the water lost is due to transpiration) during the night. But that is only part of the problem. Plant ET (evapo-transpiration) accounts for evaporation from the soil as well as transpiration mostly from plant leaves. Water management (water lost from its leaves as well as the soil surface) must account for both. This is why covering the soil with mulch of either rock or wood chips is so important. During the heat, covering the soil with two to three inches of mulch can give you at least one extra day of watering each week!             The next irrigation occurs when water from the soil reaches about 50% (half) or leaf scorching and branch/twig death may occur. The water in the soil is like the gas tank of a car, but only let the tank get half empty before filling it again with an irrigation. I haven’t had much luck growing ‘Brown Turkey’ figs. Other figs I have had no problems. Some people can’t grow some plants.             Figs produce two crops of fruit; an early crop (Briba) and a later (Main) crop. Early fig production, in my experience, is less affected by a lack of water than production of a main (later) crop. The early figs (Briba crop) are usually fine with a smaller amount of water. I don’t think it’s diseased.

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Plant Landscapes “Wet”

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Q. We had six 24″ box bay laurel trees and one 24″ olive tree planted in April of 2021, three years ago.  We water once a week for one hour with four, two gallon per hour emitters in the spring. We are not sure if they are doing well and would appreciate your expert advice. A. Thank you for telling me how you are irrigating these trees. If it were me, I would flood the area around the tree, a single time, with water now. Don’t wait. Use a $12 stationary sprinkler at the end of a hose and adjust the watering pattern from six to eight feet. Water this way for one hour. Next, I would increase the four emitters to four gallons per hour rather than two gallons per hour. I would still water for one hour.  As trees get bigger, they need more water. I believe you did not give these trees enough water when they needed an increase in water. A normal response to a lack of water is leaf drop and thinning of the canopy. I doubt it is a disease problem. I would first guess it’s not getting enough water as temperatures increase. This is normally taken care of by increasing the number of times you water per week. In your case, I think the two gph emitters did not release enough water. Replacing the emitters is sometimes a better solution than increasing the water output for ALL the plants. This way your watering time does not change. Some people plant these trees in dry soil. Make sure they are planted “wet”. Watering now with a stationary sprinkler wet all of the roots immediately. Make sure those 4 gallons per hour emitters are from six to twelve inches from the trunk of the trees. All of the soil should be wet between irrigations. These are not desert trees (xeric) but both are water loving mesic trees. Just for your information the olive tree will grow about 30 feet tall if left alone (they should be planted no closer than 20 feet apart). Olive trees can handle the heat. The bay laurel will grow about 20 feet to 25 feet tall but struggle with extreme heat. Both are considered “mesic” in their water use.

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