Q. I have several Mondale pine trees and recently noticed round bumps on some branches. I love these big trees, so I really hope I don’t have to take them out.  I deep water once a week in summer and once a month in winter and they have done very well so far. Bumps or warts on limbs of Eldarica pine A. I don’t recognize the problem to your trees as something serious. These rounded bumps are probably resin pockets in the limb. It could be caused by a nonlethal virus disease. It is also possible it could be a physical reaction to weed killers applied nearby.             Keep an eye on the tree and its growth. Apply enough water and fertilizer to get eight inches of new growth each year on older trees; 12 – 18 inches on younger trees. If the tree is doing well on your watering schedule, then keep it. Just make sure enough water is applied for it to drain 24 inches into the soil. New growth on pine are called “candles” and you can see why. This new growth should be strong and vigorous in healthy trees.             Water should be applied to at least half the area under its canopy. Add an extra irrigation when temperatures are above 110 F and windy.             One application of fertilizer in the spring of each year should be enough. When it is hot and windy (like over 110F), give it an extra deep watering. If the tree canopy is thinning the tree may need water or fertilizer or both.

Q. What is causing the “big hurt” on mulberry trees? There was considerable damage to most trees in recent years. What caused so many dead branches this and last year? Sooty canker disease  A. Mulberries are solid performers in the hot desert if they get enough water and are pruned properly. I am not endorsing their planting; they use a lot of water and the male trees release large amounts of allergenic pollen, a huge health problem for many residents. Battle of the Sexes             The female trees are not “outlawed” in southern Nevada. The male, or fruitless mulberries, are. Female trees can be planted and will produce fruit without male trees because of large amount of airborne pollen produced every year from existing male trees. Bowl of purple and white mulberry fruit in Tajikistan. Many countries I visited call the fruit “toots”. Sooty Canker Disease             We see an increasing number of mulberries with dead branches in the tops of the trees. Most of this is “sooty canker” disease. This fungal disease spreads from tree to tree on poorly sanitized pruning equipment, birds and insects. Sooty canker disease on ash. Looks the same on mulberry.             It also infects other trees besides mulberry including ash, poplar, apple and many others. Frequently, the health of infected trees was “compromised” in some way making them susceptible to an otherwise weak pathogen.             What compromises the immunity of otherwise vigorous trees growing the desert? Usually its water; a lack of it causing them to be stressed. The disease organism is transported to this weakened tree on pruning tools, or perhaps by birds or insects. This pathogen enters the tree through open wounds caused by pruning equipment, fresh openings left by dropping leaves, or through the flowers. Consider this scenario:  Sanitize pruning equipment before pruning a landscape converts from large, established trees and lawns to a desert landscape; the lawn is removed and drip irrigation is installed; large established trees do not get enough water and limbs begin dying; landscapers remove limbs with unsanitary tools; the trees become infected; disease spreads because the tree’s health is compromised due to a lack of water.             Simple solution? Sanitize pruning equipment.

Tipu tree growing in Las Vegas. Will we get winter temps below 25F? Plant this tree and you are betting we wont. Q. I have been wanting to plant a tipuana tree since I saw one in person (those pinnate leaves are gorgeous!) and I love the idea of a wide canopy.  You mentioned in a December 2013 blog that here the potential for damage from the roots would not be as concerning in Las Vegas as in other places as long as it was planted “several feet away from foundations, etc.” The location where I would like to plant is between the pool and the block wall.  The wall and the pool are separated by 19 feet.  Would planting 4 feet from the wall and 15 feet from the pool be reasonably safe? I have citrus, duranta repens, and some other cold sensitive plants that I dress in old school Christmas lights and wrap in frost cloth, so I understand it will take extra work to protect from the cold.  What do you think of my chances for success? I do love the leaves, though. Maybe I can talk myself into a purple robe locust instead.  A.  Just to be a little more clear than the section you read in my article. I am not a big fan of this tree but it has been pushed for planting in the Las Vegas area by a local nursery. You should read some of the comments from Arizona State University (Mesa, AZ) about its use in Phoenix.  Winter dieback of tipu in Las Vegas. Comments about Tipu tree from ASU I am always seeing the downside of plants because I get hit with problems all the time. The Purple Robe Locust is a good tree. It is also not desert adapted but it can handle the low temperatures with no problems. But it should be grown with woodchips as a mulch and use compost mixed in the planting soil at planting time. It is a medium water user and it will get about 35 feet tall and oval to round in shape. It is not a fast grower, not slow either but about 12 to 18 inches per year if you fertilize and water it well. Avoid putting it in very hot locations with lots of direct sunlight beating down on its trunk and limbs. Keep it full and keep the lower limbs shading the trunk as long as possible. Surround it with lots of other plants that like a similar irrigation. Texas Mountain Laurel in Las Vegas. Can have a spring insect problem but easily controlled. Consider Texas Mountain Laurel, Texas Olive, Desert Museum palo verde, Red Push Pistache, etc. Even ornamental pear aka Callery pear. A better fit for our climate. All trees have problems but these would have fewer tree life threatening problems.

Q. I am using an inexpensive soil meter to help me judge went to water again. I redid my landscape to include cacti, ocotillo, agaves and other types of desert plants. Do I let my meter peg to 1 before watering again or is 2 to 3 okay? A. I have promoted the use of moisture meters for helping gardeners “get a handle” on when to water plants. For non-desert plants, like many of our trees and shrubs, let the soil moisture drop to about 50 -60 % before watering again. If the meter is divided into 10 equal units, this would be about “6” on the meter’s scale. The scales are relatively accurate             Desert plants that are not cacti, like Mesquite, Palo Verde, Acacia and leafy succulents, the meter can drop a little bit lower than this before watering; about 40-50% or about “5” on the same scale. Another example of reading soil moisture with an inexpensive moisture meter..             Cacti is in a category by itself. I think you are about right. Let the soil moisture drop to between “2-3” before watering again. Because cacti store water inside their modified stems and leaves, they give a visual indicator when their water is running out; the outside shrivels. That is a dead giveaway it’s time to water. A third example of using a soil moisture meter for gauging when to water again.             When I am irrigating non-desert plants like fruit trees in a soil that is new to me, I take three readings in different locations around the tree and use the average. I don’t let any readings drop below “5” and I will water if the average is about “6”. After I get the “rhythm” of seasonal water use, I seldom need it after that. Soil moisture meters I use alot for approximating soil moisture for irrigation Reotemp Soil Moisture Meter Link Lincoln soil moisture meter but the price has jumped up too high for me recently Probes that are longer are more versatile             The other thing I do is push the probe of the meter into the soil slowly. I want to measure soil moisture near the surface of the soil and watch how it increases with depth. This technique helps me understand how fast water is leaving the soil. When to Water             There are two questions you need to answer when watering: when to water and how much to apply. Soil moisture meters help mostly with the “when” to water.             I judge how much water to apply by pushing a thin metal rod, like 3/8 inch rebar, into the soil. It slips into the soil easily when it’s wet. For trees and shrubs, apply enough water to penetrate 18 to 24 inches deep. For lawns, flowerbeds and vegetable gardens, 12 inches deep. Two foot tall shrubs, vines and groundcovers, 12 to 18 inches deep.             These are inexpensive meters andnot meant to last forever when pushed into our soils. Once you get the “feel” for when, you won’t need it often. Just occasionally when you aren’t sure. Steps 1.         Insert it in the soil slowly. Get moisture readings as you slowly insert it into the soil. This gives you an idea how the soil is drying out with depth. Newly planted seeds, trees, shrubs, need water frequently but only a little. As they grow they need water less often (deeper) but more of it. 2.         Take three soil measurements in different locations. Insert it between emitters (if that is what you have). Otherwise insert it anywhere, randomly, above the roots. 3.         Observe your moisture meter readings as you slowly insert it and at the depth of the roots. For flowers and grass, this will be about (slowly) 6 inches deep. Remember that plant roots use water using the 40-30-20-10 rule…40% of the water they use is in the upper quarter of their rooting depth, 30% from the second quarter, 20% from the third quarter and 10% from the bottom quarter. If the plants are grass, flowers or vegetables the roots are divided into upper quarter (zero to three inches deep), second quarter (3-6 inches deep) third quarter (6-nine inches deep) and bottom quarter (9-12 inches deep). Tree roots are 18 to 24 inches deep so adjust your “quarters” to this depth. This is why it is important to push it into the soil slowly. 4.         Take three readings like this. Average them. Use this value to determine when to water. 9-10    =   Wet. Don’t water. 7-8    =   Moist. Don’t water. 5-6    =  Water. 3-4    =  Water desert plants 1-3    =  Dry. Your plant is dead unless it’s a cactus. Buy a new plant. How much to water?  Look at the size of the plant. Can you plant it in a 1 gallon container? Water it ½ gallon. Can you plant it in a two gallon container? Water it with one gallon of water. Can you plant it in a 5 gallon bucket? Water it with 2 ½ gallons (round it to 3 gallons). Got the idea? 3/8 inch diameter rebar used for measuring irrigation depth inexpensively Trees and large shrubs are more difficult to judge the container. Space emitters every 18 to 24 inches apart under AT LEAST half of its canopy. Water long enough for the water to drain 18 in deep. The easiest way to judge this is using a 3/8 in rebar, pointed or sharpened (flat if you cant sharpen it) and push it into the soil after you water. It will push easily to the same depth of the water.

Q. About five years ago our HOA  -executed a conversion project and removed the grass, replaced it with rocks. In some grass plots there are some 20 years  old pine, ash, olive and privet trees. In order to secure water supply for these trees, the contractor installed water lines around each tree in circular formation, and covered them with  wood mulch in a radius of 5-6 feet around the trunks. The rest of the areas rocks was placed.  Now the new  HOA Board thinks the mulch is unseemly and plans to remove it and replace it withe rocks.I would like to ask your opinion on this. A.  I can understand why HOA members (I’m assuming the board represents the members) would not like a polkadot pattern of woodchips with a background of rock mulch in their landscape. That is not my intent when I recommend woodchips used on the soil surface around some trees. I would agree with your members that this could look rather odd and decide to cover the area instead with one type of mulch. I would also argue that woodchips applied to the soil surface beneath large trees and occupying 5 to 6 foot diameter is defeating the basic purpose of using woodchips versus rock mulch. If woodchips are used, they need to be applied to a much larger area under the trees than a 6 foot diameter circle. Their application is meant for soil improvement rather than aesthetics. The type of mulch selected for landscapes makes a huge impact on the general texture, “look” and aesthetics of a landscape. Woodchip mulch on top of desert soils combined with water will improve both structure and chemistry enough to improve plant health and growth. You will find the feeder roots growing into this type of soil. I’m going to respond to your question in increments. If this wood mulch is a “bark mulch” rather than a “woodchip mulch” then its only contribution is aesthetics. Bark mulch adds very little to soil improvement. Its use is almost 100% aesthetic. Using bark mulch has its pluses and minuses but on the minus side it does very little to improve the soil and so it is quite similar to rock mulch in that regard. Large decorative bark mulch is used for aesthetics and not soil improvement. Photo courtesy Viragrow Inc. www.viragrow.com Woodchip mulch is very different from bark mulch or rock mulch in that its primary use is long-term and its focus is on soil improvement. It’s very handy, and I would argue irreplaceable, for some trees when changing a landscape from lawns to “desert”, a.k.a. rock mulch landscapes. Now lets jump over to your list of plants. The one tree on your list you will have problems with is the Japanese Privet. This tree will be very tricky for it to look good in a landscape covered in rock mulch. Actually, it may have trouble growing well even in woodchip mulch because the problem is soil moisture rather than soil improvement.  Japanese privet looking its best in a rock landscape. In our desert climate, JP looks good in a lawn where the soil is moist continuously and small amounts of organics are added back to the soil each year. This happens just by having the lawn growing around it. When the lawn is removed, it starts to suffer. I would be surprised if it looks good even after the first couple of years in a rock mulch conversion from a lawn. This tree definitely will have trouble growing well in a rock landscape. Depending on which ash tree, this is another tree that may struggle growing in soil covered 100% by rock. Most ash trees grow better in lawns than in rock mulch. I don’t think you will have serious problems with pine or olive trees growing in soil covered by rock. They will need fertilizer applications now that the lawn is gone. A suggestion, use a very coarse rock (1 inch or larger) of the same color under these trees when replacing the wood mulch. Then add compost underneath the canopies of these trees growing in coarse rock mulch every one to two years and water it in.  If you use a “rich compost” such as Viragrow’s, you can skip annual fertilizer applications and save a little bit of money.

Q. I see some of the resorts with gorgeous masses of jasmine, and in many places it seems like they are pruned into low mounds for borders. How do I avoid the exposed leggy parts — will the rootstock regenerate if I simply prune it all the way to the base?  What time of year to do that if it would work? Star Jasmine picture sent to me. This star jasmine needs more room to grow! A. The picture you sent helped a lot. Star Jasmine performs best probably as a vine rather than a groundcover but it can be used for both if given enough room to grow. The star jasmine in the picture is planted too close to the hardscape (concrete sidewalk, stone edging, etc) to be left there. This plant can be hedged but I would not recommend it. Hedging this plant with a hedge shears will make it always look “twiggy” or full of brown stems and brown leaf edges that you can see.   Yellowing star jasmine as a small shrub due to desert soil lack of organics, alkalinity and poor drainage Star Jasmine is actually a fairly large plant that can grow 2 feet tall and 10 feet wide if left sprawling on the ground. This means that these plants should have about five with spacing between plants and planted about 5 feet from a hardscape. If I were pushed to fill in the area quickly I certainly would not put them any closer than 3 feet apart and 3 feet from a hardscape.   Star jasmine as a vine full of new growth because of  organics in the soil, fertilizer applications and watering They don’t look terribly good in our eastern Mojave Desert soils surrounded by rock mulch lying on the surface of the soil. They usually become yellow, scraggly in a few years because of soil and water drainage problems. This is a plant that prefers to grow in soil amended with compost at planting time and the soil covered in woodchip mulch. Light pruning can be done anytime of the year when there is a problem with their growth invading some areas or becoming to dense. But the best time to prune them to optimize flowering is immediately after they finish flowering in late June or July. Pruning them then gives the plant a chance to rebuild itself for the next to flowering cycle which should begin in late spring.   Star jasmine will  become very woody if pruned continuously with a hedge shears To do the type of pruning you are suggesting, basically a type of rejuvenation pruning or cutting it way back, should be done in late winter or early spring just before new growth begins. You can cut star Jasmine back very hard, so that 4 to 6 inches of old growth remains sticking out of the ground, and get it to regrow again into a plant full of new growth and flowers. Pruning it as a vine is different. As a vine you want to retain its old growth and “balance” the remaining growth while encouraging new growth where the woody parts of the vine are appearing. Basically, you want the vine to be green and full of flowers from top to bottom. This requires a combination of different pruning techniques, fertilizing and watering. Where the vine is dense and full of growth (usually near the top) thinning pruning cuts are made and in the sparse areas, heading cuts are done. Thinning cuts remove entire stems back to the woody stems. Heading cuts are made in the sparse areas (4 to 6 inches of growth remains) leaving a stub for lots of new growth. Pruning cuts are followed with a fertilizer application (a rose or tomato fertilizer will work) and watered in.

Q. This year our apricot tree hardly produced enough fruit to bother making jam. Is it possible our warmish winter was a factor? We don’t know if this variety is a low chill variety since it came with the house. Has anyone else mentioned low production with apricots this year? Apricot fruit closeup. This is what good tree ripened fruit should look like. A. We have about 12 different varieties of apricots at the Ahern Orchard and I oversaw about 10 varieties at the University Orchard. These apricots ranged in chilling hours but received enough cold winter temperatures to satisfy their chilling requirements for over 20 years. The light fruit set was probably due to our cold, wet spring weather.             If the tree was loaded with flowers but produce very little fruit, it was a pollination problem, not because of a lack in winter chilling. Apricot skin disease due to spring rain and high humidity             The weather was mostly cold during February when apricots and many peaches were flowering. Bee activity was light due to cold weather and overcast skies. Yes, bees are needed for pollination.             I was watching the flowers in February and visits by honeybees were very light when flowers were open. The early apricot varieties, Katy and Flavor Delight (really an aprium), set a very light fruit crop and were harvested over the last three weeks. A light fruit set was true also of some plums and pluots. It depends when flowers were open for pollination.             Cool weather during fruit development also affects the sugar content of fruit. Cool temperatures result in fruit with less sugar content and more acidity. This is also true of grapes and many other fruit.             It was not a good year for some apricots and peach varieties if they were flowering during cool weather and skies were overcast. Our spring weather was strange and not normal for us.             I am confident next year we will be back to normal and apricots should have a heavy fruit load.

Q. I have been wanting to plant a tipuana tree since I saw one in person (those pinnate leaves are gorgeous!) and I love the idea of a wide canopy.  You mentioned in a December 2013 blog that here the potential for damage from the roots would not be as concerning in Las Vegas as in other places as long as it was planted “several feet away from foundations, etc.” The location where I would like to plant is between the pool and the block wall.  The wall and the pool are separated by 19 feet.  Would planting 4 feet from the wall and 15 feet from the pool be reasonably safe? I have citrus, duranta repens, and some other cold sensitive plants that I dress in old school Christmas lights and wrap in frost cloth, so I understand it will take extra work to protect from the cold.  What do you think of my chances for success? A. Just to be a little more clear than the section you read in my article. I am not a big fan of this tree but it has been pushed for planting in the Las Vegas area by a local nursery. You should read some of the comments from Arizona State University (Mesa, AZ) about its use in Phoenix. http://www.public.asu.edu/~camartin/plants/Plant%20html%20files/tipuanatipu.html If you plant this tree please be prepared that: It may freeze back during some of our winters in Las Vegas when winter temperatures get below 25F. In the past our winter temperatures have dipped regularly into the upper teens. It is not low water use. Expect that this tree will use more water than desert adapted trees of a similar size. So plan on using it in a part of your landscape that is wetter and not surrounded by rock mulch typical to desert landscapes. Tipu dieback This is a big tree. It can get to heights probably 35 to 50 feet tall in the desert. It routinely grows higher than this in nondesert landscapes. /tipu canopy So if you are fine with all this then I would not plant it closer than about 10 or 12 feet from a house foundation, patio, driveway, wall or sidewalk. When you plant it, focus the applied water in areas away from these areas. Try to leave at least three feet of dry soil between the tree and these locations. Nine times out of ten you will be fine closer than this but it is the 1 in 10 that concerns me. It should not be used in a hot part of the yard with lots of reflected heat and light. Sapsucker damage on tipu I have seen this tree in backyards that are protected from wind and with plenty of plants around it. I have seen them up to 20+ feet tall and looking pretty good but these are protected backyards. Tipu growing in backyard These are relatively new trees for Las Vegas so there is not much history on them. But I am always concerned when planting any long term tree that is freeze damaged at 25F in a climate that historically gets lower temperatures than this. I have a saying that I tell my students…be prepared to spend more time, energy and money on plants that may not be sustainable in our desert climate. I like to see trees that are key elements to a landscape that will survive winter temperatures at least to 20F.

Q. I have one pomegranate tree in bad shape. The leaves are turning yellow and then brown, underneath the veins are pink. This is one tree out of my 50 that looks like this each other tree look great with a lot of new growth. Any ideas what could be happening with this one tree? A. Yellowing of the leaves could be caused by several things including flooding the soil too often, poor drainage and planting too deeply. However, if these trees have been growing for several years, you have done nothing differently and suddenly the leaves turn yellow, it could be damage from weed killers used in the area.             Remember, apply weed killers only when there is no wind and temperatures are cool. Best times are usually spring and fall. Some weed killers can vaporize into the air when sprayed during the heat. Slight wind movement causes these vapors to drift onto the leaves of valuable plants nearby and damage them.             Never spray weed killers when the wind is strong enough to move plant leaves. Use leaf movement as an indicator whether to spray or not. Early morning hours are usually best.             Some worst offenders in this category are the lawn dandelion and similar weed killers. These types of weed killers move easily with air movements and cause leaf distortion, leaf yellowing, leaf death and even plant death.             If the plant is actively growing when weed killers accidentally drift onto the leaves, then wash the leaves with water as soon as possible. Diluting weed killers with water while the leaves are still wet helps prevent damage.             All you can do at this point is wait and see what happens. Fertilize it normally and water it. But remove the grass at least 2 to 3 feet from the trees and fertilize it with nitrogen fertilizer. Another possibility could be salinity…salts…but you should see some leaf tip browning.

Q. I have two of these plants at my front door area that are two years old. They only bloomed the first year and this year they are very green but no flowers. How do I get them to flower?  I tried cutting the water for 2-3 weeks but that only made them grow and greener. I would appreciate any help and suggestions you may have. I have attached pictures of them. A. Flowering requires at least 8 hours of direct sunlight everyday. If they are not getting enough they will be a nice green, grow well but flowering will be greatly reduced or eliminated. Over-application of rich soil amendments or high nitrogen fertilizers can also delay or decrease flowering but make a nice green plant. They might flower the first year because flowering was already started or flower buds were in progress from the nursery. If you don’t have enough sunlight in that spot you will have to move them to a sunnier location or out further into the light. If this was from high nitrogen fertilizers or soil amendments just let the nitrogen get used up and they should start flowering when that happens. When fertilizing, use a tomato or rose fertilizer and not a lawn type fertilizer. The others have the right balance of nitrogen and phosphorus for flowering.