Q. We are growing the Celebrity variety of tomatoes in our garden here in Las Vegas and decided to cover them this year with a mesh tarp for shade because the sun has scorched them in the past.  However, we noticed the vines are growing but the tomatoes are not very big and they are not ripening like they usually do.  Are they supposed to have complete sun? What do you suggest? Providing too much shade causes poor growth and reduced fruit or flower production or none! 30% shade vs 60% shade. A. The amount of shade that you provide to tomatoes is critical for continued production of fruit. Shade cloth is typically categorized by the percent of shade that it provides. For flowering plants you should provide no more than 30 to 40% shade or they may stop flowering and setting fruit. Plants that do not flower can handle more shade, up to about 50 or 60%.             You didn’t tell me what percent shade you are giving tomatoes but I suspect it’s too much. Light shade, 20 to 40%, is hard to find locally. Usually you have to order light shade for crops. You can provide shade by also using lathe instead of shade cloth.             In northern climates we used to use snow fence. To get 50% shade, remove every other lathe from a solid ceiling of lathe. To get 25% shade, remove two and leave one. Chain-link fence with PVC slats gives you about 75% shade. I think you get the picture.

Q. You mentioned that citrus trees are often grafted. Are full size trees grafted like dwarf trees? Do I need to remove anything? The trees are about five feet tall. Will I have more success getting fruit from full size trees? Remove suckers like these from the base of small trees as soon as you see them.This fruit tree is watered with drip irrigation from in-line tubing. Wood chip mulch is covering the soil.The tree was planted bare root and painted with white wash to prevent sunburn. A. All citrus bought from a nursery are grafted, full size trees as well as trees sold as dwarf or semi dwarf. Seldom are they grown on their own roots for a variety of reasons. The most common is because of our cold winter climate and protecting the rootstock from freezing. Some of this benefit from freezing is passed on to the rest of the tree. Root stock dogleg on grafted fruit tree.             Fruit produced from dwarf trees can be the same size as standard size trees if the tree is managed properly. If you look at the bottom of the tree you will see a “dogleg” where the top tree was grafted to the to the roots of a different tree. You will see this dogleg on many ornamental trees as well.             Anything growing from below this “dogleg” (on the rootstock) should be removed as soon as you see new growth. Young trees frequently “sucker” from this rootstock and these suckers must be removed. Pulling them off rather than cutting them is better. As the tree gets older, it frequently stops suckering as much.             Enjoy what you can. Citrus is “iffy” in our climate. Some years you will have fruit, other years you will not. Some years they may freeze to the ground and other years sail through the winter without damage. 

Q. I am trying to grow an avocado tree.  I have it in a container and it’s now 22 inches tall.  When is the best time to transplant and what is the best way to take care of it in our desert? A. As you are probably aware, avocados are “iffy” in the Las Vegas climate. Probably a little worse than citrus regarding surviving winter cold. It depends on which avocado you are growing.              With that said, I would put the container in a protected area away from extreme cold during the coldest part of this coming winter. Around the first week of March, I would plant it in the ground. Make sure you amend the soil and do not fertilize it after August 1. http://xtremehorticulture.blogspot.com/2014/01/solutions-for-home-avocado-production.htm lhttp://xtremehorticulture.blogspot.com/2016/03/avocados-for-cold-desert.html

Q. I’m considering watering my little lemon tree every day during the summer months. Is this good or bad? The tree dropped two-thirds of it’s leaves a month after planting. That was three months ago. It has stabilized, and I currently water it every other day on a slow drip. (4 gallons per watering) Should I water every day in June, July, and August because of the 100+ temps? A. I have noticed some problems with citrus the first year after planting from containers into the soil. There was a lot of relief yellowing, leaf scorch, leaf drop and some dieback. This happened even though there was wood chip mulch at their base. Once small amounts of water were applied daily they did quite a bit better during the summer. You will not have a problem watering every day if the soil drains water quickly. You will have a problem watering daily if the soil holds water for a long time. You might see some advantage to watering with small amounts of water every day. I see that sometimes on very young citrus but only for the first year after planting. I’m sorry to say, “it just depends…”. If you have not done it, try applying 3 to 4 inches of wood chips around the bottom of the tree and you should be able to water every other day with no problems even on the hottest days.

Q. This is really great information that you put on your blog!! Thank you so much for doing this, and it gives me a bit more hope about expanding my home orchard in Phoenix.  http://xtremehorticulture.blogspot.com/2015/11/special-fruit-tree-orders-no-longer.html http://xtremehorticulture.blogspot.com/2011/04/recommended-fruit-tree-varieties-for.html How many chill hours are you getting where you are located? Specifically related to Pluots, you are recommending some with some pretty high chill hours, such as the Flavor Supreme which is listed on DWN as 700-800 chill hours. But as you mentioned above that may have a lot to do with location and micro climate. Also for Apples, Pink Lady is a pretty late ripener, and I’ve heard that late harvest don’t do as well in the extreme heat of Phoenix, something similar to where you live. But again, I’m hoping the placing them is certain cooler places within my backyard and trying to create a micro climate that is a bit more forgiving to these fruits could have a large impact as well. Would love to hear you take on the points point. Thanks again for putting some much time into this. A. Thank you for appreciating the hundreds of hours that it took over a period of one and a half decades to put this list together. Many kudos to the Master Gardener volunteers who supported it.  I will try to address each of your questions separately.             Most of the trees used were donations by Dave a Wilson Nursery, Tom Spellman in particular, who worked with us since 1996. This orchard is located in North Las Vegas Nevada at right about 2000 foot elevation.             The orchard is exposed to the North West by cold winter winds which helps explain why citrus was not included on this list even though it was tried. Las Vegas is not citrus country but many people further south in the Valley have had success with some citrus and even limes and blood orange in warm microclimates.             Our chilling hours are somewhere between 300 to 400 hours per year. You are exactly right. If you take chilling hours literally many of the recommended trees should not produce in this climate yet they have for over 15, now going on 20, years. Some of these so-called high chilling hours tree fruits have shown no sign of a lack in chilling hours.             Tom Spellman was the first person to bring this idea to light for me. It challenges many preconceived ideas about chilling hours and there has been much speculation and even disbelief in this information.             Personally, I believe that chilling hours are more important in some types of fruit and even some varieties than others. Is chilling hours important? Yes, definitely. Have we followed chilling hour recommendations to literally? Yes, definitely.             Too many, Phoenix and Las Vegas have similar climates if you don’t live in either of these locations. You and I both know that as far from the truth! Phoenix is a totally different animal from Las Vegas but I believe there is a wide variation in how plants view this difference. I believe most apples are more prone to chilling hours than peaches, nectarines, apricots and plums and their crosses.             I don’t know all pink lady apple performs in Phoenix but it is an outstanding Apple in the Las Vegas area. Like pomegranates, this particular Apple seems to have better flavor quality as temperatures drop. In our harsh desert climate it seems to develop a thicker, tougher skin but the flavor quality of the “meat” is superior. It is worth giving a try in Phoenix, Yuma, Parker, Bullhead or Lake Havasu.             I think planting apples in areas of the landscape that avoid the late afternoon sun is a good idea. Contrary to some information out there, if your soil has lower amounts of organics in it, amend it with compost at the time of planting. I also believe you will see huge benefits if the soil is covered with wood chip mulch under its canopy to a depth of at least 4 inches.             Keep the mulch away from the trunk for the first five years of the trees life to avoid collar rot. If rabbits are problems, protect the tree from rabbit damage with 1 inch hexagon with chicken wire for the first five years as well.

Q. Last year we bought a Myers lemon and planted it in a large pot. We got more than 30 lemons off this little tree. I noticed a lot of sap near the base of the tree, then a bunch of furry little things on the trunk and some branches. They scrape off easily. I’m guessing they are the cause of the sap. Cottony cushion scale on lemon More of the same A. You are right. This is cottony cushion scale, an insect, on your lemon tree. Those little furry things are homes to the scale insect. They live under those furry things where they are protected from pesticides and predators.             Once in a while they come out and build a larger, furry home or find a mate. When they do, this is called their “crawler” stage, when they are most vulnerable to pesticides and predators.             What’s interesting are the ants that you didn’t mention. These small, scale insects feed on the sugary sap inside the tree. While feeding on this sugary sap, a sugary concoction comes out the other end which some ants love.             These ants move these insects to new growth in the spring where feeding is a lot easier than at the tough, woody base of the tree. In these new locations, ants “herd” them like cattle and protect them from marauders.             From your picture it doesn’t look like you have very many on this tree yet. Take some alcohol and a cotton swab and dab them off. If there were lots of them you could spray horticultural oil several times during the year, particularly during tree growth periods.             These oils suffocate the crawlers and keep it from spreading while the older ones eventually die off. Apply these oils three or four times during the year at times when temperatures are cool. By the way, it also helps a lot to control any ants in the area.

Q. Could you provide me with a copy of the mulch trial you conducted on fruit trees several years ago? You randomly applied mulch to different fruit trees and grew some without mulch. I lost this information. This is a picture of the mulch trial performed at the University Orchard in North Las Vegas. A variety of fruit trees were planted with and without 3 to 4 inches of wood mulch at their base. They were all watered and fertilized the same. Mulch was wood chips made from trees that were removed from residences. Mulch was donated by First Choice Tree Service. A. I conducted this mulch trial in 2009 – 2011 with the First Choice Tree Service on bare root fruit trees planted in our desert soils according to my specifications using 50% compost mixed with raw desert soil in a volume to volume ratio. Look at the change in soil color after a very short time when wet soil is covered with woodchip mulch. The wood chips “melt” into the soil with time, decomposing and adding nutrients, stimulating microorganisms and make a healthy environment for earthworms.             Mulch is a layer or blanket applied to the surface of soil. Mulch can be made from wood, bark, rock, newspaper, cardboard or even plastic. But if this is applied to the surface of the soil and left undisturbed, it is considered mulch. This is Redwood decorative bark mulch. Bark mulches do not provide the same nutrients as woodchip mulch which is much better. Would chip mulch is made from the entire tree, not just from the bark.             A 50% mixture in a volume to volume ratio, means, for instance, a 5 gallon of compost mixed with a 5 gallon bucket of raw desert soil. In a few months of watering this results in a raw desert soil with less than 1% organic matter increasing to between five and 10%, not 50%. If you want to know why, attend some of my classes.             Peaches, plums, pluots were planted in holes about 3 feet wide and deep enough to accommodate their roots and no deeper. The holes were not deeper than this because water added to planting holes drained water in less than six hours. This fruit tree was covered with a layer of rock mulch about 2 inches deep. Organics that were added to the soil at the time of planting will be gone in 3 to 5 years. These organics will be replaced with a mineralized soil that has no organics in it, soil life is dying and water drainage is getting increasingly worse.             Fruit trees were planted using a 50% (volume/volume) mixture of compost and raw desert soil. All fruit trees were staked the first growing season and pruned in the same fashion after planting. No fertilizer was applied except for phosphorus to the bottom of the planting hole at the time of planting.             All fruit trees were watered the same using a 3 foot wide basin, 4 inches deep, filled with water. All trees were staked and surrounded by chicken wire to prevent rabbit damage. Irrigation basins around fruit trees, if they are not being watered by drip irrigation, should be level, large enough to be half the size of their canopy and 3 to 4 inches deep. Irrigation basins must get larger as the tree gets larger to provide enough water to the tree.             Half of the fruit trees were randomly mulched with a 4 to 6 inch layer of wood chips made from local trees removed from home landscapes locally by First Choice Tree Service. The other half of the fruit trees were surrounded by bare soil.             Mulch was kept away from the tree trunks a distance of 12 inches. The mulch was made from a variety of local trees not including palm and mesquite. Mulch like this with a variety of different types of wood, not 100% bark, makes a great addition to the surface of desert soils. Don’t let this valuable commodity go to waste in our landfills.             At the end of the first growing season, fruit trees surrounded by surface mulch were more than twice the size than those without surface mulch.             This mulch is available for free on a serve your own basis from the University Orchard in North Las Vegas and made available to the Orchard by First Choice Tree Service. If you want a large volume delivered, contact First Choice Tree Service.

Q. I’m planting new fruit trees this year. I’ve noticed there seems to be a consensus that backfilling should be done with only native soil, without any amendments. However, is there an exception in Las Vegas where the soil is exceptionally poor? A. This does not apply to desert soils with extremely low organic matter content. Some desert soils are okay to plant in directly with few problems. Others are not. Your soil organic matter content should be about 5%. If it is lower than this, add organic content to the soil such as a good quality compost.  This is the kind of desert soil we typically see in the Las Vegas Valley. This soil is very light brown and cannot be done dry with a shovel. You must use a pick. This soil has nearly no organics in it. To plant in the soil without adding organics is sheer disaster.Some people call this mistakenly “caliche’. It is not. It is a sandy loam with zero organics but digs like caliche if not amended. Mix it with the soil taken from the planting hole OR bring in a soil mix and use that to fill the planting hole around the tree roots or container “ball” of roots. Be careful of adding too much organic content to the soil. This can work against the establishment of roots in the surrounding soil.  This soil is in a valley in northern Arizona. It is also light brown and extremely hard to dig. But the soil is very productive once it has been reclaimed with organics and water. It is also a sandy loam with virtually no rocks, a perfect soil for crops once it is been reclaimed. This is the situation with research done in Oklahoma, Arizona and other states. These practices of “not adding organic matter” to the soil at planting is from their research with soils significantly high in organic matter. This is the orchard in North Las Vegas covered with wood chip mulch 4 to 6 inches deep. The wood chips come from trees that would normally be taken to the landfill. If these trees are chipped and applied to the surface of the soil where there is water, the soil becomes dark brown in less than one growing season. Remarkably, we even find worms. Many soils of the Mojave Desert with very low rainfall are extremely low in organics. Soils in the desert that are relatively high in rainfall or were previously farm land (under irrigation). These are frequently already high enough in organics and adding more does little, if any, good. Using the deserts of the Southwest as an example (Sonoran, Mojave, Chihuhuan, Great Basin) they range in historical rainfall from 4 inches to over 10 inches of rainfall each year. This is a 250% difference depending on locale!!! Of course we will see different types of plants and a difference in plant density and canopy size when we compare desert environments with a difference in rainfall of 250%!!! This is reflected in soil differences there as well. We see differences in organic content, salts, pH, etc. The Sonoran Desert is different from the Mojave Desert primarily because it receives 250% more rainfall. This rainfall leads to a higher density of plants, plants which become larger and are different from the plants in the Mojave Desert. The presence of plant life and rain lead to higher organics in the soil which also contributes to better plant growth. The Mojave is really a desert! How do we know what the organic content of a soil is? We can send it to a soil testing laboratory and spend maybe $75 to $100 and wait for three weeks for a reply or use our noggin and get a rough approximation. The soil testing lab will give you a precise amount in the sample sent to them. If the sample sent to them is representative of the soil that interests us, the it may be fairly accurate. But, garbage in, garbage out. If the sample is NOT a good representative of the soil that interests us then it is garbage. Rich, productive soils are dark brown in color, not light tan. The presence of organics in soils turn light tan soils into dark brown soils. Adding 50% organics such as compost to a desert soil does not result in 50% organic matter content. It will probably be somewhere around 5 to 10% when it’s all done. Look at the soil. Soil color is a pretty good indicator of soil organic content. Rich soils, full of organics are brown to black. The lighter the color, the less organics in it. If the soil is moist and dark brown, you probably don’t have to add anything. If it is light tan or very light colored, even when moist, it probably needs organics added despite the recommendations from Oklahoma or Arizona. This is a true desert soil, so low in organics that its color is almost white. What to do? Add organics, in this case in the form of compost or manure. Mix it all together and water it. To get a really productive soil you will continue to do this for the next 2 to 3 years. The soil will settle down and start giving you big benefits. Dig in the soil. If you need a pick to dig or a shovel barely scrapes the surface, AND it is light colored….ADD ORGANICS!!!! Add organics in a ratio of about 1:1 by volume or container. Add a five gallon bucket of compost to this cement-like soil. Adding organics/compost in a 1:1 ratio (v/v) will NOT result in 50% organic matter content but probably in about 3 to 5% content after watering, settling, and growing for one season. Next year add 25% by volume (v/v) if it is a garden soil or apply about one inch of compost to the soil surface around a plant and lightly scratch it into the soil surface, and water

Q. When should you stop cutting asparagus? We’ve had a good crop again but seem to have quit harvesting too soon in prior years so want to go as long as possible, we enjoy eating it! Asparagus is harvested or cut just above the soil surface. It is best not to leave the severed spears too far above the soil surface or it gets in the way of weeding and other management practices. Cutting below the soil surface allows diseases to enter the plant. A. The textbook answer is 6 to 8 weeks of cutting and then you should let it go and rebuild its crowns beneath the soil for next year’s harvest. That information was back when asparagus spears were thought to be marketable only if they were the diameter of your thumb. Three grades of asparagus based on diameter of the spear. The highest quality asparagus has spears large in diameter. The smaller diameter asparagus is becoming popular as a lower-cost alternative. Asparagus produces a lot more small spears than the largest ones.             That’s kind of changed and now we see asparagus much smaller than that and marketed as such. The other answer is to continue to harvest until you see a noticeable decrease in the diameter size of the spears. When they start to get too small for harvesting, stop and let the beneath ground part of asparagus rebuild itself. When planting asparagus the crowns are planted 12 to 18 inches apart and 8 to 10 inches deep. I like to plant them on either side of drip tape or drip tubing in a triangular pattern with rows that are wide enough to walk between and harvest.             Asparagus will rebuild itself better if you can provide some nutrients as the crowns are putting away storage for next year. So after harvesting, laid down at least an inch of rich compost or you can also use manure. Purple asparagus is a novelty which brings a little higher income but purple varieties do not produce as many spears. They have a higher sugar content and are a bit sweeter than the green types. I stick with varieties that have done well in the hot Southwest such as the University of California or UC types. Purple Passion has done well for me.             The crowns should be 6 to 10 inches deep depending on the soil so laying manure on top of these areas should cause no problems. Make sure you water it in and don’t water too often because the crowns are fairly deep. Put them on a similar irrigation cycle to fruit trees if they are planted deep.

Q. About three weeks ago I laid tall fescue sod in my backyard.  I put some top soil under it for a base before I laid it.  I religiously watered the sod twice a day. Today I removed the sod because it was all dead. No roots emerged. Where did I do wrong? A. I am not sure you did anything wrong. If you kept the sod wet after it was delivered and planted it right away, it should have grown. Sod comes either rolled like this or in flat rectangular strips. Make sure the sod was recently harvested and kept moist. It should be placed in the shade until it is planted. I would never buy fescue sod during the summer months. Warm season sod such as Bermuda, paspallum, zoysia, buffalo or St. Augustine could be purchased during summer months.             I have seen problems with sod when it was laid on very hot ground. During the middle of summer, bare soil can be 165 to 170° F, hot enough to “cook” the roots of grasses laid on top of it. If you spray Roundup on bare soil, wait 7 to 10 days before laying sod or planting seed because this chemical can damage it. This sod was laid on hot, dry soil during the middle of summer and not watered until after all of it was installed. The hot, dry soil seared the roots of this sod and caused it to die in patches.             If soil temperatures are hot, lay the sod during very early morning hours. If it must be done during the heat, lightly spray the soil with water just ahead of where you are laying it. The spray of water helps cool the soil as you’re laying it. The downside is the soil can get quite muddy.             The best time to plant fescue seed is from the middle of February until about May 1 and then again from mid-September until middle November. With sod, extend the season a couple of weeks longer in the spring and later into the fall. Fescue sod is sometimes grown with plastic netting and a very thin layer of soil. The sod is held together by the plastic netting which makes it very light. Sod roles can be huge and installed much like a carpet when sold this way.             Topsoil put down for sod should be at least 6 inches deep or more. Another option is to apply 100% compost, 1 inch deep, and rototill it into the soil as deep as you can. Roll the soil before laying the sod. After laying sod, roll it again with a water roller or steel drum roller after it has been irrigated two or three times. Rolling it and keeping the soil wet helps to “knit” the sod into the soil beneath it. When installing sod make sure that the seams, where the sod comes together, has no gaps in it. It is always a good idea to water the sod as it is being installed and then roll it so that the roots and soil make good contact.             Pull on the sod after two weeks and see if it is staring to “knit” into the soil beneath it. Knitting is growing roots into the soil from the sod. If it is knitting, then water less often but water it longer.