Q. A couple years ago our builder planted a multi-trunk Chilean Mesquite tree in our side yard which borders a street. The tree is planted 12 feet from the house but is only 5 feet from a block wall. I am concerned this tree will become huge and its root system may disrupt the wall since there are several irrigated shrubs on the other side. I am thinking of removing it while it’s still young and replacing it with a “tamer” tree. A young mesquite tree in good landscape form and enough space to grow. It can get 50 feet tall with irrigation and fertilizer. A. That’s a good call and very forward thinking on your part. This tree will grow quickly to about 50 feet with an equal spread. If you are going to replace a tree, this fall would be the right time to do it. Remember, planting smaller sized trees will overtake planting larger trees in one or two seasons of growth. No reason to buy larger trees unless you need immediate impact from them. Texas or Mexican olive (Cordia boissieri) with irrigation. A smaller tree for smaller areas than mesquite.             If your home is a single-story home, consider two small desert trees to replace a single big Chilean Mesquite. Plant them a distance apart equal to their mature height and about half their mature height from the home. If this tree area is on the south or west side of the home, make them winter deciduous for winter heat gain. All you want are trees large enough to shade the walls and windows during the summer. Little leaf cordia (Cordia parvifolia) as a very small street tree in Las Vegas. Another landscape tree much smaller than mesquite and native. Use two of these small trees instead of one mesquite for shading exterior walls.             Tree roots follow the water. Roots will grow wherever you apply water, or they find wet soil. Keep applied water 3 foot from the foundation of the home and the wall. It might not be a bad idea to install a root barrier between the trees and the home’s foundation and block wall. But watering lengthwise and parallel to the home will encourage the roots of the newly planted trees to grow in that direction as well. Tree roots do not have to grow in a circle under the tree.

Q.  Several years back my father and I planted two Raywood ash trees in each of our yards. Now both of trees have longitudinal gashes along the stems that kill many of the smaller branches. Last year I  found the same problem on one of my rose bushes. Per the recommendation of the nursery I sprayed a systemic containing imidacloprid and clothianidin on the trees. My picture showing cicada damage to small stems on Acacia. A.  This sounds like egg laying damage by the Apache cicada; those high-pitched insects you hear buzzing in about July. The insecticide you are spraying will not correct this problem so stop using it. This female cicada is not laying eggs…yet..             Apache cicadas make that buzzing noise so they can mate. Once they have mated, the female lays eggs in a slit she creates on the branches. If these slits cause enough damage, the twig dies. The eggs then hatch, and the insect drops to the ground where they burrow into the soil and feed on plant roots. Lots of different trees are favorites, your ash trees (sounds like the roses, too) being among them. Cicada empty skin or exoskeleton left behind on anything they can find when they emerge from the ground.             Spraying the tree with an insecticide, or drenching the soil with one, is not a good idea. I think your best bet is to give your trees as much chance to heal themselves, after the damage is done, as possible. Their best chance of healing from this type of damage is the presence of fertilizer in the soil and adequate water during the heat. Of course, scaring these insects off to other trees during mating time would help.             Make sure these trees are fertilized in the spring and bump up the amount of water applied when you start hearing the buzzing noise. You might even try watering every other day during this period to help the tree recover from cicada egg laying damage.

Q. One of my pomegranate trees has very pale leaves on one of its branches and dark healthy green leaves on the others.  I put nitrogen fertilizer on both sides of the tree plus we did put a balanced fertilizer on it and some compost. Pomegranate with one stem off color. What to do? Read on. A. When one branch of a plant is dramatically different in color while the other branches are healthy, it means that whatever is causing this problem is at the bottom of that sick part. Since borers are not common in pomegranate the cause is most likely manmade or a disease problem.             Look at the main stem just below the yellow leaves. The leaves below this point should be healthy while the leaves above it should be sickly. If the entire stem is sick, then look at the stem just above and below where it enters the ground.             If the entire stem is sick but alive then I am guessing it is damage below this area from tools, machinery, or disease. If the stem is totally dead then it involves a lot more guesswork. Mower damage, if planted in a lawn, can cause this type of damage. This type of damage makes the plant worse during hot summer months when everything is more stressed. Line trimmer damage can cause the same type of damage as mowers. Diseases like “collar rot” that “choke” the stem, when the plant is kept moist all the time, can cause the same visual damage as mowers and line trimmers.             What to do? If there is mulch surrounding the stems or anything that can act like a sponge and hold water, pull it back and away from the stems 6 to 12 inches and let this area dry out.             Never water daily. Always give the soil a chance to “dry out” before watering again. The only areas of a landscape that need daily watering are lawns, vegetable gardens and flower beds.             Whatever the cause, this yellowing stem probably should be removed. Sanitize your lopper, pruning shears or saw with alcohol and remove the stem at ground level. It is best to do it in the fall or winter, but you can remove it now on pomegranates with no problems.

Q. I found a tomato variety that’s doing great in my garden called Heatmaster. I can tell it’s a determinate type because it’s loaded with tomatoes right now, pretty much all at the same time. I’ve read determinate types die after the tomatoes ripen. Is that true? Can I root it from a branch and plant it next month for a second crop even though it’s a determinate type? A. Yes, Heatmaster is a determinate type regarding how the plant grows and produces tomatoes. But be careful. You can root this tomato from suckers but creating new plants from suckers is difficult to do in this climate. Try it and see how you do but it can be done.             Determinateand indeterminate tomatoes have their pluses and minuses. (FYI…there are indeterminate Bush tomatoes.) You can usually tell if its determinate from where the fruit is produced. Determinate tomatoes produce their fruit at the ends of stems while indeterminate types typically produce along its stems. Most of what I heard about heat tolerant tomatoes like Heatmaster is regarding their taste.             Determinate types of tomatoes usually do not die after they set fruit. Tomato plants are tropical perennials. Death is typically from disease or problems associated with high temperatures. A determinate type tomato is good to have in the garden, but indeterminate types work as well. Just handle them differently.             So-called heat tolerant tomatoes like Heatmaster, Phoenix (also determinate) and others were bred for warm southern climates and not for the hot desert. They might set fruit at temperatures a few degrees warmer than normal but not when the air temperature gets into the 100s we sometimes see. Collection of tomatoes grown in Las Vegas in 2005 including Sweet 100 Cherry tomato, Snow White cherry tomato, yellow pear, Ivory Egg heirloom and Black from Tula heirloom.          If you have cool weather during fruit set then any tomato will set fruit including heirlooms like Mortgage Lifter and Brandywines. That’s why you may have good luck with hard-to-set tomatoes some years. Some of it is the “luck of the draw” as far as weather goes but a favorable garden environment that limits wind and wide temperature swings helps. Be careful about relying on one year of good production to make future buying decisions.             Plant several types of tomatoes rather than focus on one variety. Cherry, grape and pear tomatoes are the easiest to grow and set fruit the easiest. Most of these are indeterminate types. Probably the next easiest are the plum type tomatoes like San Marzano and Roma. For some reason disease prone Early Girl (indeterminate), hybrid Celebrity (bushy but indeterminate) and even Burpee’s 70-year-old Big Boy (indeterminate) are good performers in our finicky desert climate.             Make sure there aren’t other reasons for a lack of fruit set such as low humidity and a lack of pollinators. Plant herbs to attract pollinators like rosemary, basil, thyme, mint, and fennel. Put out water in flat trays and clean it often. Bees visit many of the flowering herbs and clean water they can haul back to their hives when tomatoes start flowering.

Q. I have a 30-foot tall Chilean Mesquite tree that looks nice and healthy but has a 2-foot long dry black streak on its trunk. What is it and what’s the problem? Black discoloration of mesquite trunk from my pictures A. These dark streaks on the trunk are a common occurrence on mesquite, particularly if it had been pruned in the past. In common vernacular, the tree “bled” after it was pruned. If your tree otherwise looks healthy, then there is nothing to worry about. Wetwood aka Slime Flux               Mesquite gets a minor bacterial disease problem called wetwood, a.k.a. “slime flux”, which causes a similar staining on large limbs and the trunk. But the black stain is constantly wet and “smelly”. Slime flux is a bacterial infection deep inside the tree which causes a wet “yeasty” oozing to flow from limbs that attracts flies. It’s spread from tree to tree by lots of things including “tree trimmers” that think they are arborists. It’s not a lethal disease problem for the tree, but it may cause owners some angst. Slime flux bacterial disease on African sumac.             I have a picture of a mesquite tree with a black streak on its trunk on my blog. I will repost it for you to look at and compare.

Q. What is the difference between “Red Tip Photinia” and “Fraser’s Photinia”? Red Tip or Frasers Photinia A. My understanding is that they are the same plant, just different common names. The Latin name has both Photinia and Fraser (fraseri) in it. This explains why it is sometimes called Fraser’s Photinia. Because it’s new spring growth  is red, it is sometimes called Red Tip, or Red Tipped Photinia. I prefer the name “Red Tip Photinia” because it describes the plant better than calling it “Fraser’s Photinia” or just “Red Tip”.             When in doubt about the plant go back to the Latin name to see if it’s the same plant. Plants can have several different common names but only one agreed upon Latin name.             By the way, this plant is considered “mesic” (needs to be watered more often than “xeric” plants), grows better in amended soil and doesn’t like to grow in hot spots or surrounded by rock.

Q. About a year ago you helped us diagnose a spider mite problem on our creosote bush. We took care of that as you directed. The results were encouraging and seemed to get the problem under control. However, we think the mites have come back with a vengeance and considering a severe pruning to revive it. Creosotebush cut down probably with a grader in the front and unpruned creosote bushes in the back. A.  Creosotebush can be cut back to a few inches above the ground and it will grow back after a few occasional waterings. Look at the creosotebushes mowed off near desert roads probably by a road grader from the DOT. Because they were cut down and got some extra water from the road when it rained, they came back like gangbusters; dense and green. Predator/Prey             What concerns me more is why the spider mites got out of control in the first place. Creosotebush has its share of spider mites naturally, but they are frequently controlled by predators such as other insects and mites. However, in your case, the balance between “good guys” and “bad guys” got out of hand with the “bad guys” winning.             The problem with spraying a pesticide is killing off the “good guys”, then the “bad guys” get out of control because few or no predators are left. So, we usually avoid spraying pesticides unless we don’t have any choice. Cutting Back Creosote             I like your idea of cutting it back and letting it regrow. But I think you also must do something different or the spider mites will just be back again. Weed Control             Control weeds in the area. Spider mites like to feed on many kinds of plants including weeds, and these can play host to a growing population of “bad guys”. Secondly, be careful of watering too often. Creosote bush should never be on an automatic irrigation system because it just doesn’t like to be watered that often. Water it no often than four times a year with three of those irrigations during the hot months.

Q. Is it common for the Chitalpa tree to partially defoliate in the summer? What would be the optimum amount of water for 15-foot Chitalpa tree growing in Kingman, Arizona? Not the readers chitalpa but s picture I had. A. Chitalpa, like some African sumac, is notorious for leaf drop in the middle of summer. According to several authorities from New Mexico and Arizona this is common with this tree. Bacterial Disease             According to the plant pathologist from New Mexico State University, this tree has a bacterial issue that causes some of its water tubes to get plugged. This causes the leaves on the tree to get scorched like it’s not getting enough water and in severe leaf scorching, the leaves drop.             It’s similar, if not the same, disease we see on grapes called Pierce’s Disease. You can try giving it more water all under its canopy and see if that helps. If it’s a lack of water because it’s not getting any you will see the tree improve. Anyway, apply enough water to wet the soil under the canopy a depth of 2 feet. Spread to Grapes             From what I understand there is no cure for this disease and  ach plant has it because of how it’s propagated. Some scientists think this disease may be transmitted by a small insect similar to a leafhopper. So, get rid of any weeds growing nearby to the tree. It is possible this disease could be spread from your Chitalpa to nearby grapes. The symptoms are similar; leaf scorch and leaf drop but in grapes its eventual plant death.

Q. I have a hibiscus in a 20-inch clay pot with wrinkled flower buds, small leaves, and leggy stems. The hibiscus gets filtered light on my South facing patio and gets hand watered every other day. This is a hibiscus growing in a 20 inch pot.  Some hard renewal pruning is needed and repotting the plant. A. I looked at the picture of your potted hibiscus and I think it is getting large for its container. This is a 20-inch container and the size of the main stems are larger than thumb sized. That’s because you are pruning all the small stems from the outside and not pruning the larger stems toward the center. Your pruning style is also the reason it’s getting “leggy”.             I think you have two options; you can either get a larger container or cut the hibiscus smaller. Let’s me explain how to do “renewal pruning” on it first. I think that’s your best option. Renewal Pruning             Renewal pruning, cutting deep inside the shrub and removing larger wood, results in a flush of sucker growth from the remaining “stubs” that eventually fills the open areas. This flush of sucker growth will be succulent and produce lots of leaves and flowers. You then select the best suckers to establish a new plant. Basically, you are “renewing” an older shrub by reinvigorating it.             Prune the main stems as low as 4 to 6 inches from the soil. This sounds  dramatic but in hibiscus it results in a flush of new growth from below the cuts. Doing this causes it to sucker below the remaining stubs with new growth filling these open areas. In previous pruning  you were removing from the perimeter. Do renewal pruning as soon as weather cools off in the fall and new growth will cover the deep pruning cuts before it gets cold. Repotting             After you finished renewal pruning your hibiscus, gently ease it out of the container and remove the soil from around the roots. Keeping the roots moist, prune a couple of large roots and replace the soil in the container with fresh soil. Repeat this renewal pruning and repotting process about every three or four years to keep it young and vigorous.

Q. All the YouTube videos say when tomatoes form and we get a rain, they tend to start splitting. We are on a drip system and have steady water all through the growing  season. Any help you can give would be appreciated. Tomato fruit splitting A. To prevent cracking or splitting of the largest fruit, the best thing to do is to turn on the drip system just before it starts to rain. I know this sounds counterintuitive but here is the scientific explanation.  Science Behind It Rainwater enters the fruit and causes it to split because of differences in salt concentrations inside the fruit, which include the sugars and starches, and the rainwater. Turning on the drip system when it begins raining puts water into the fruit, diluting the salt concentrations, and helps reduce cracking or splitting of the fruit.             The second thing to do is harvest large fruit close to maturity before it rains and let it ripen inside the house. The fruits most affected by rain are the larger ones and usually red ones. These two things will reduce fruit splitting but not eliminate it unless you are just plain lucky.