Q. I have a question about the health of my nectarine tree. I had this tree planted 17 years ago and it has thrived every year since…until this year. Normally it is totally covered with blossoms and new growth. This year there are only a few scattered signs of growth. Most of the tree is barren. What could cause this? Is the tree dying? Nectarines are close relatives to peach. Peach and nectarine are short lived trees primarily because of borer problems in the Las Vegas valley. A. The most common reason for sudden tree death is borers. Look for peeling or flaking of the bark usually on the west or south side of the tree. They are actively feeding on the trees right now but the dieback usually shows up when it gets hot.  I see it is in the lawn. Other reasons can be damage to the trunk from lawn mowers or line trimmers and then attack by borers. You might try a soil drench of a borer control chemical from Bayer. Then the trunk needs to be protected from direct sunlight. But if it is peach, that is pretty old for a peach tree. Anything over 15 years old I consider old for peach due to borers. Peach or nectarine. It’s the same DNA just the fuzz is missing. They live about the same length of time. If you use the Bayer product you cannot eat the fruit from this tree until it is no longer applied. It would have to be applied now.

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Q. I have a Granny apple and Meyer lemon tree. I just saw that I have a bunch of these bugs on the flowers. I would like to know if I should kill them or leave them alone. I also have bees pollinating the flowers so I don’t want to spray any chemicals that may harm them. If I have to remove the bugs is there any way to do it without harming the tree or the bees? A. Those are aphids sucking plant juices to feed their young. Their numbers will continue to grow until it gets hot.  Horticultural oil or dormant oil is sprayed on trees and shrubs during warm and windless days in the winter. It eliminates soft bodied insects like aphids. You missed the winter application of dormant oil or you would have eliminated nearly all of them. Not much you can spray now without hitting some bees once the flowers are open like that. Wait until the flowers have formed apples and then spray.  Alternative: You can use an oil spray like a dormant oil or soap sprays if it is below about 90F and the flowers are gone and fruit has started to form. Or pull off the flowers and spray and let the flowers reform again later. They will. A. 

Citrus is meant for subtropical and tropical climates. Learn which how to select, grow and maintain this type of fruit in our desert. Citrus grown in the Las Vegas valley

Join me on this episode of Desert Horticulture. I discuss the long-lasting effects that spring freezing temperatures can have on plants. Winter cold damage and bronzing of the leaves

Q. Because of the winter cold weather, I move my citrus trees growing in containers into my garage where it never gets below 40.  I added three fluorescent lights fixtures with grow lux bulbs per light fixture and they are hanging a few inches above the trees. Will this be sufficient light to keep the trees from being starved for light? A. Although it’s less intense than outdoor sunlight this will work. I’m guessing you keep these citrus trees in your garage all winter long. But I’m wondering if you even need all that! Interior of a peach flower showing the ovary. A fresh, good looking ovary after a possible freeze tells you it will probably produce a fruit.            Winter freezing temperatures low enough to kill flowers normally start around mid-December. Usually by mid-February these temperatures are over. Although rare, sometimes we never experience freezing temperatures anywhere in the valley. Infrequently these temperatures are “patchy” and can start in mid-November (as they did in 2020) and can stretch into mid-March (as they did in 2021). Recording Thermometer  Inexpensive recording Taylor thermometer with two temperature probes. It used to run about $12. Accuweather app for cell phone Do you see why I recommend putting a recording thermometer in your landscape! I also recommend downloading a weather app on your phone for predicting upcoming freezes. Different landscapes experience different temperatures. Oftentimes these different landscapes follow different weather patterns. These weather patterns determine your level of success in our climate. It would be much simpler for growing citrus if our climate was colder or warmer. But it’s not. Low Light Levels Can Substitute for High Light Levels I’m also wondering if your citrus even need the extra light. If temperatures are cold in your garage then the entire plant goes into “hibernation” and there is little need for light. For many plants this “magic temperature” is around 40 to 45° F. Also, the darkness inside the garage can delay flowering. Because the intensity of light is so low, I would leave these lights on for 16 to 18 hours every day. Long-term low light accumulation can sometimes substitute for short-term highlight intensity (think sunlight). Because of these long light intervals, you might see earlier flowering in these trees.  

Q. A horticulturalist suggested to put my dwarf citrus trees in the biggest pot I have room for or can afford and they will be happiest there. A person at a local nursery said to not move a tree from a small pot to a much larger pot and suggested the new pot be no more than 2 inches bigger in diameter than the small pot. The two questions seem to be in conflict. What do you think? The most important practice comes about three to five years after planting into the container; replacing soil and root pruning. A. Both answers are acceptable and pot size is not an issue as long as it is big enough. What is more important is the maintenance needed every few years for plants growing in containers. The soil in the container gets “worn out” and the roots need to be trimmed. Perhaps think about these containers like an aquarium; every few years plants in containers need to be removed, fresh soil added, the roots trimmed, and the plant repotted. This maintenance practice reinvigorates the plant and helps it live longer with fewer problems. Selecting Citrus for Containers Calamondin, or calamansi in the Philippines where it is native, is a small citrus that is suitable for containers. But it is sensitive to winter freezing temperatures. When selecting citrus trees for containers make sure the tree is a dwarf or smaller in size. Smaller citrus like lime trees, calamondin, and kumquat, although variable in how much cold they can tolerate, are naturally small in stature. Oranges, lemons and larger citrus on dwarfing rootstock can also work but may be difficult to find. Look for the word “dwarf” on the label. Containers Get Hot in the Desert Also important is the transfer of heat from the sunny side of the container to the roots. Temperatures in the summer can be 170°F on the exposed side of the container. Consider growing container plants inside another container so the inside container is protected from direct sun by a fancy decorative exterior container. The shade from the exterior container prevents the sun from heating up the interior container.

Q. I just planted a Lisbon and Meyer lemon in full sun. Do I need to put shade cloth over them in the summer? I put shade cloth over my raised bed vegetable garden. They are planted along a northeast facing wall and not surrounded by rock. Eureka Lemon growing in Las Vegas. Eureka lemon is a true lemon. A. It’s a good location for fruit trees but I’m not sure how your citrus will perform in your landscape locale. Its touch and go in our climate. Much of their performance depends on the winter and spring temperatures of your landscape location. If temperatures are very low during the winter, Lisbon and Meyer trees might both get killed. Meyer lemon is more cold hardy, but in a very cold location, or during a very cold winter, it can be damaged or worse. If there are spring freezing temperatures, you might see less or no fruit produced on one or both trees. Probably Meyer lemon which is not a true lemon. It doesnt have that lemon shape, it is round instead, and it shows off its orange heritage when it ripens but still tastes like a sweet lemon. ‘Lisbon’ is a normal lemon tree. ‘Meyer’ is not. Meyer lemon fruit tastes like a lemon but is actually a citrus hybrid with sour fruit. ‘Lisbon’ is 5 or 6 degrees more tender to winter freezing temperatures than Meyer lemon so it may need winter protection in your landscape locale when Meyer doesn’t. Shade Protection? Citrus doesn’t need shade protecting it from our desert sun. Citrus grows in full sun in the Yuma area, so it doesn’t need shade cloth here either. However, the first year after planting it might be a little shocked from its transfer from coastal California nursery to the harsher Mojave desert so it may develop some leaf yellowing or leaf drop the first year. Give it a chance to acclimate to this desert area which is no worse than growing in Yuma if the soil is improved at planting.

Q. I’ve had a dwarf Minneola Tangelo tree for about 4 years that gets morning sun, but I’ve gotten fruit off it only once. I’ve had an orange tree for about 1 year and a half that gets full sun; it had blossoms, but they all fell off before the heat of summer even began! I planted a pomegranate tree in full sun this past Mother’s Day.  When I bought it, it had blooms on it; they also all fell off. Unknown young pomegranate variety after maybe two years in the ground. Some pomegranate varieties are precocious…meaning they produce fruit early while other varieties produce fruit the first year.  A. There are several different issues with your fruit trees. The Minneola Tangelo flowers only once in January and February. The same will be true of most sweet oranges. If there are freezing temperatures during this time at your landscape locale, then you may get little to no fruit when this happens. When your landscape gets winters with no freezing temperatures then each flower will produce fruit. Late freezes            It only takes a couple of degrees below freezing for a very short time to eliminate the flower and fruit. Multiple freezes during the spring results in total fruit loss. You may see fruit from these trees in the future, but it depends on the occurrence of spring freezing temperatures. Be patient growing most citrus here. Citrus is more productive when there are no winter or spring freezing temperatures such as in Yuma, Arizona. Periodically we get winter freezing temperatures that can outright kill different types of citrus trees. The only reliable citrus for producing fruit in our climate are the so-called kumquats. This is because they are very cold hardy and flower all through the year. Not Old Enough Pomegranate loss of fruit is a different story. Pomegranate flowers through most of the year because the flowers are produced on “current season wood”; new growth and not last year’s growth. Some pomegranate varieties are more precocious than others and you will see fruit the first year they are planted. Other varieties produce fruit in the second or third year after they are in the ground. Just be patient and they will produce fruit. Plants frequently produce flowers but no fruit when they are young. It is an indicator that next year they may start fruiting.

Myer lemon (not a true lemon) fruit ready for harvest. Its orange color and round shape shows off its orange fruit heritage. Why doesn’t my ‘Meyer’ lemon tree produce any fruit?  I was reminded of this question when I estimated the fruit production this year in a Las Vegas Orchard. I use a particular variety of pluot called ‘Flavor Supreme’ as an “indicator tree” for predicting the probable fruit load that year. I saw no fruit developing and I saw no remnants of flowers on these trees. I knew there was a late freeze that came through that orchard during the spring, probably two or three weeks ago. Tearing open a flower soon after suspected freeze damage will tell you if the fruit will fall off dead or it is alive. In this case the ovary inside is green so it shows the flower will most likely produce a fruit.            How did I know all that and how do I relate it back to ‘Meyer’ lemon? First of all, recognize it only takes a 1 or 2°F difference in temperature between having a tree loaded with fruit versus having a tree with few fruit. If this temperature difference comes along two or three times during the spring when it’s trying to flower, then voilà, there is no fruit produced that year. All Flowers are Sensitive to Freezing            The most tender parts to freezing temperatures of any fruit tree is its flowers. When flowers are open is the time when it is most sensitive to freezing temperatures. The tree itself is usually fine but not the flowers. If a very light freeze occurs in the spring only once when the tree is flowering, then fruit production is reduced. If a light freeze happens two or three times, maybe a week apart during the spring, then the fruit is probably eliminated for that year. However, if there is a single “hard” freeze (4 or 5 degrees below freezing or more) as flower buds are “awake” then, most likely, all fruit will be eliminated for that year.            Flowers are killed by freezing temperatures depending on their stage of development. Flower buds during the dead of winter are very tolerant to freezing temperatures. But in the spring, when the plant begins to “wake up” from its winter sleep, they become more and more sensitive to freezing temperatures as they approach opening. Open flowers are the most sensitive to freezing temperatures; 1°F below freezing for a very short time kills the single chance it has for fruit. Once a flower dies, it cannot produce fruit. If the flowering time of a fruit tree lasts three weeks, then it has a better chance to produce fruit as more flowers continue to open. If only 5% of the flowers are needed to produce a full load of fruit and all the flowers are dead, there is no fruit for that year.