Xtremehorticulture

Xtremehorticulture of the Desert

‘Tiny Tower’ May Be a Smaller Variety of Italian Cypress

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Q.  I have a space that has a height limit of 10-12 feet.  I want to plant some columnar trees that won’t grow too tall.  I realize that Italian cypress would work but would have to be trimmed to limit their height. Are there others that might work in our Las Vegas climate? For example: ‘Emerald Green’ Arborvitae, ‘Sky Pencil’ Holly, and any others? A.  To get a truly evergreen hedge in this climate is tough. We may have winter cold that kills the leaves of many smaller trees followed by leaf drop. ‘Tiny Tower’, (aka, ‘Monshel’ and ‘Compacta’) from Monrovia Nursery (a production nursery) claims to be only 10 feet tall and 2 feet wide and very slow growing. With age Monrovia claims it will grow 25 to 30 feet tall and 3 feet wide. Others do confirm 20 to 25 feet at “maturity”. What “maturity” means, as far as age of the plant, was not made clear. I would guess that it grows at one foot per year if not watered more often and given fertilizer. Watch out for the flopping of new growth. That tells you are watering too often. Monrovia said it was taken as a dwarf “sport” from an existing Italian cypress. Las Vegas USDA zone classification is 8A through 9B, so it is well within those hardiness zones.

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Benefits of Wood Chip Mulch for Gardens

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Q. I have been hearing about the benefits of wood mulch for my garden. What type of wood should I look for and where would I find it?  Do I work it into the soil like my lawn cuttings or just spread it on the surface? A. Three things are important; soil temperature, watering so the soil stays moist, and the size of wood chips. The smaller the wood chips, the faster they rot or decompose. Temperatures warmer than 55F speed up how fast these particles “rot”. Dryness slows down how fast the wood chips rot. The wood chips need it warm, moist and should be small to decompose quickly. For instance, sawdust rots too fast but wood chips too large may rot too slowly. About 1/4 inch to 1/2 inch is perfect. The source of the wood chips is also important. Please don’t confuse “bark” and “wood”. Never use bark for wood chips unless you want it to look pretty and float or blow away. A mixture of wood and bark is okay but not straight bark. Bark chips are mostly decorative. Wood chips are not decorative (pretty) at all. I would call wood chips “rustic” if I were selling it. Bark mulch “looks” are the main reason its bought. When wood chips are on the soil surface it is called mulch. Wood chips used as mulch are not pretty. It’s functional. It’s okay if wood chip mulch is larger. In fact, you want wood chip mulch to be large. When small wood chips are mixed with moist soil, they are no longer seen. They slowly, over time, become the “organics” part of the soil or organic matter. The rate of decomposition depends on the size of the wood chips, how regularly moist the soil becomes, and soil temperature. Lawn clippings are “green” (not “brown” like woodchips) when first mowed. Grass clippings rot quickly compared to wood chips. Wood chips have a carbon to nitrogen ratio of around 300 or 400 to one (300 or 400 carbons to one nitrogen). There is a lot more carbon present compared to nitrogen. To get wood chips to release their nutrients locked up, you must add some nitrogen fertilizer. Lawn clippings have a carbon to nitrogen ratio of about 40 or 60 to 1. There is a lot more nitrogen fertilizer in green grass clippings than in wood chips. “Green” mulch doesn’t need extra fertilizer. “Brown” mulch does. What does that mean to you? As wood chips rot or decompose you must add nitrogen fertilizer to it. Grass clippings don’t need any added nitrogen. Grass clippings act like a complete fertilizer when it rots or decomposes. It is the complete package. Use finely ground wood chips when mixed in the soil and add some nitrogen fertilizer with it. Use small chunky wood chips (1/2 inch and smaller) when mixed in the soil.

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Depth of Watering

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Q. Many of your articles talk about the depth of the water when watering. Having the drips on top of the ground can make it hard to get the water to the desired depth.  If you want watering at 12″, what is your opinion of putting a piece of plastic pipe to that depth, then just put the drip line down the pipe so it drips at 12″!  If you are worried about spreading the water out, you could always put a larger pipe or plastic junction box at the bottom. A. It does not change how much water it needs. The surface 3 to 4 inches of surface mulch nearly eliminates evaporation from the soil (the E part of ET). I would not use any devices that divert water deeper. It just costs money and adds to the watering confusion. It will need the same amount regardless. Most plants rely on water that fills the soil from “top to bottom”. The depth of applied water depends on the height of the tree. Generally speaking, small trees (less than 20 feet in height) require less water than large trees (more than 40 feet tall).             Did you ever hear of the 40-30-20-10 rule in a landscape? Landscape plant roots range from about 12 inches to three feet deep. The taller the plant, the deeper its roots. Divide landscape plant roots into four equal parts (quartiles). The quartile closest to the soil surface uses about 40% of the applied water, the next quartile uses about 30%, the next uses about 20% and the last quartile uses about 10% of the applied water.             Quartiles are human inventions. As water in this 40% quartile becomes more difficult to extract, the plant uses the next quartile, and the next, and finally the last. Plants don’t use any more “effort” than they need to! For nondesert plants we schedule a new irrigation when this water is about 50 to 60% gone.             So you see, all landscape plants require water to fill the soil so that all their roots are wet from “top to bottom”. Just remember, the taller the plant the more water is applied!

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‘Red Baron’ Peach Flower Color

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Q. After watching the beautiful flower color of ‘Red Baron’ peach on your YouTube channel, I want one. Where can I get it? I tried to find it locally but couldn’t find it. A. Try online. I found it at Groworganic.com. It is a yellow fleshed variety that flowers in early or mid March and produces fruit somewhere around mid-July to August. They will ship the tree to the Las Vegas location without soil in late January or early February, but is very difficult to find locally. Plant it (wet) as soon as you get it. Planting it wet should give you about one week of its water needs when planting at that time of year. Purchasing it can be done on this website: https://www.groworganic.com/ I would give the fruit from that tree a high three or possibly four out of five stars. Out of 25 to 30 varieties of peach trees, only three peach varieties consistently received a five out of five stars. The fruit was very good but did not receive a five-star rating. It is a good reliable peach tree for our area. There are many peach trees to select from that produce fruit in our area. Others include the white fleshed ‘Babcock’, ‘Arctic Supreme’, ‘Galaxy Donut’ and ‘Indian Free’ among others. More traditional yellow-fruited types (and taste) include ‘Eva’s Pride’, ‘July Elberta’, ‘Belle of Georgia’, ‘Kaweah’, ‘O’Henry’, and other varieties. Select those that flower after the second week of February to mid March and produce their fruit before mid-August. For backyards and in the desert, always buy them on dwarfing rootstocks. Avoid genetic dwarf trees. Buy them 3/4 inch or smaller, the smaller the better. If they don’t have future limbs at your knees or lower, prune them to knee height after planting to encourage lower limb growth.

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Young ‘Fantasia’ Nectarine Diseased?

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Q. My ‘Fantasia’ nectarine survived over the winter. It got leaves and blossomed. Now the leaves aren’t looking great, and the branches are developing black tips almost like they’ve been burned. Is that likely to be black fungus? If I need to dig out the tree and replace it, when would the best time be to do that? Are we too close to summer to try that now? A. This was a rough time for plants this winter. All through the winter this tree should not receive a deep watering more often than once a week. Some time in February is the time to give mesic (water loving) trees (all fruit trees are mesic) a solid watering of watering once a week. How much depends on its size but make sure the roots get water 18 to 24 inches deep. All plants pretty much follow a 40-30-20-10 rule with their roots. First make sure the fruit tree was planted correctly (planting hole dug or the soil at least loosened! three times the container width) and the hole backfilled with an amended soil. Make sure the tree was staked and watered in, the soil around the tree covered with a mulch of some sort. Next, we can address your tree issues. With this very low desert humidity, any leaf of stem disease will not last long. If the tree looks good other than the leaves, let it go. Let the warm, and eventually hot, weather do its job. The leaves look a little yellow so make sure it was fertilized properly in about four weeks if needed. Make sure there isn’t a borer problem present. Nectarines are “glorified peaches”. They can be a problem in peaches and nectarines. By the way, ‘Fantasia’ nectarine fruit got pretty low marks from me at the University orchard regarding tasting the fruit. Not the tree, it did well, but the taste of the fruit.

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Arizona Cypress Pruning and Pest Problems

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Q. Should I cut out the limbs with all the brown needles on my Arizona cypress? The needles stopped falling off immediately and the one’s left don’t look nearly as brown and dry. I have no idea how to go about pruning these huge trees. Don’t know if it would help. What do you think? A. I would wait a bit. It is now the beginning of April. I don’t know what will happen in a month.

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Kadota Figs are Treated Like Any Fig in the Desert

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Q. I have a Kadota fig tree that gives lots of figs, but they are either hard as a rock or suddenly get mushy and fall off the tree. What am I doing wrong and how can I get some edible figs A. There are at least two crops of figs, an early crop (Briba crop) and a later crop (Main crop). My guess is that the early crop is getting enough water (when its cooler) but not the later crops. Remember, figs are water loving crops. As temperatures get warmer, they require more water. Also, as your fig tree gets bigger it will require more water. Prune them small and harvest the fruit from the ground when possible.

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Skeletonizers on Grapes a Late Spring Problem

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Q. I have some pest problems on my grapes that I think is grape leaf skeletonizer, but it made holes in the leaves. Is this the same skeletonizer or do I have a new problem? A. The grape leaf skeletonizer is an adult three quarter to one inch or so moth which lays eggs in clusters and is a problem with grapes every year. The short-lived adult moth, along with the small eggs, don’t do any damage. It’s the larva which burn like matchheads if they fall on your skin. It’s these larvae that “skeletonize” grape leaves that causes all the damage. These young black and yellow larvae glide across grape leaves and turn these leaves into “skeletons” three to five times every year. Skeletonizing grape leaves is what gets them bigger. This can start from April or May of every year in Las Vegas depending on their populations. If you don’t get some control of them early with sprays of spinosad or Bt, their populations may continue to get larger and larger. There is another insect problem with grapes. That is the grape flea beetle which “chews” holes in the leaves. Most of the time it can be confused with “skeletonizers”. This is because they occur at the same time, but don’t create the same type of damage. Flea beetles chew holes in leaves. They don’t skeletonize leaves. And, unlike ‘skeletonizers”, they cause grape leaf damage, at the most, twice year. Oftentimes, just once in the spring. With “skeletonizers” the preferred spray is spinosad. You can use Bt (Bacillus thuringiensis) sprays and most of the time they will work. I like spinosad sprays because they will get leafhoppers as well which Bt does not. For grape flea beetles any insecticide works. But spraying them with an insecticide isn’t always the answer. Usually, unless the infestation is heavy, just waiting three weeks is enough. The population of grape flea beetles will pass without spraying. I oftentimes will just wait for three weeks but not for the skeletonizers. You must spray and spray early. Don’t forget to spray the undersides of leaves early.

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Chitalpa Died Back

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Q. Our chitalpa tree underperformed last year after ten years of growth. This year (2024) it is 2/3 dead. How do I tell if it was verticillium wilt disease or bacterial leaf scorch disease that killed it? If leaf scorch, can I replace it with another Chitalpa? If verticillium wilt, what flowering tree resistant to verticillium wilt would you recommend? A. Chitalpa is a mesic hybrid between the catalpa tree and desert willow. In case you haven’t seen it, I would refer you to New Mexico State University’s fact sheet on chitalpa and bacterial leaf scorch. https://plantclinic.nmsu.edu/documents/xylella-fastidiosa-factsheet_reduced.pdf My guess is that this tree was infected, or already infected, by this bacterial disease. I would NOT replace it. I would pick a different tree other than chitalpa. Why? It is probable it would get reinfected with the same disease if it hasn’t been propagated with it. A different disease you mentioned is a widespread fungal disease called verticillium wilt. According to UCCE Sonoma County…. (Verticillium wilt is a fungal disease) caused by a soil-borne fungus that enters a plant through its roots and disrupts its vascular system. Symptoms of this disease include: With some trees they display discolored wood. This disease is less likely a problem with chitalpa. Both eventually kill the tree or at least they are infected. Verticillium wilt is a fungal disease that causes many trees to wilt rapidly. This fungus (disease) can live in wet or moist soil for long periods without showing any signs. The disease plugs the xylem, or water-conducting tissues, of the plant. In both cases, (bacterial leaf blight vs verticillium blight) whichever disease it might be is a moot point. Both diseases are lethal to the trees. The tree will eventually die and there is nothing you can apply to save it. If the tree has either of these diseases, it should be removed. I would not recommend planting a new chitalpa. That is unfortunate because chitalpa is one of the few trees that is smaller, can handle our heat and fits nicely into our small tree palette even though I put it in the “mesic” category of water use for trees. With bacterial leaf blight (more likely) it is spread by insects. It is spread by the same insect responsible for a grape and oleander diseases. Because it is primarily spread by insects, it is pressing to remove the tree in summer as soon as possible. Verticillium wilt disease (less likely) is not spread by insects, so it is less pressing to remove it asap. It is related more to wet soil and usually not spread by insects. In both cases they are always lethal and not curable. Verticillium disease resistance is less likely in small trees in the rose family, pines (gymnosperms), and palms (monocots). Since this disease is more related to wet soil, I would not plant anything in the same hole but avoid planting in the same spot. If I had to replace the tree with something in the rose family, I would find a plant for that spot that gets afternoon shade and prune it to the height needed. Smaller trees less likely to display problems in desert landscapes to verticillium wilt include: Purple leaf plum, larger boxwoods, hawthorne, many fruit trees like peaches, plums, and apricots, some of the smaller conifers, crepe myrtle, citrus, ornamental pear and pear trees, katsura tree, palms, flowering cherry, pyracantha, honeylocust, and some of the hollies. All of these trees are mesic in their water use. Don’t water them daily!

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Don’t Confuse Containers with Landscapes

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Q. A little over a year ago we bought our current house in North Las Vegas. The folks who sold us the house took a large slope (facing West) in the back of the property and put a retaining wall to level the yard. Plants in that area are dying. After reading your comments in the paper, we are equating this space to a “giant pot” cooking everything to death. We are fairly certain there are irrigation problems that are contributing to the current situation and will get addressed once we have a plan in place. A. My comments were made about containers, not soil in the ground. Soil in the ground stays cooler than containers because extra heat is routed to the surrounding and deeper soil. Small containers (20 gallons or less) directly in the sun can get overly hot on the west and south sides of a home. I was suggesting using larger containers in those places and watering them daily (if they can drain) before the soil and roots get hot. The use of surface mulch 2 to 3 inches deep also keeps soil in the ground from getting too hot. I suggest increasing the depth of any surface mulch used in that area. Most of your plant problems are probably related to irrigation and plant selection for those areas. The south and west sides of a home are typically in the hottest spots. Make sure you use deciduous plants to cool the west and south sides of a home. Shading doesn’t include the roof but rather the walls and windows. You can always add plants for interest later as you figure out your personal “needs and wants” of your landscape. Two-story homes may require larger trees than single-story homes. This can mean more water is needed on those sides. On these south and west sides make sure these plants are “heat tolerant”. Trees and shrubs on this side should be “bulletproof” to the heat (120F) and cold (20F) we can experience. This is the reason I suggest using tried-and-true “desert plants” for these areas. Trees should be a distance apart, and from the house, of at least three fourths of their mature height. Smaller shrubs of various sizes, colors and textures are randomly planted beneath these trees to create interest and make use of the water supplied. Other things to consider on that side that don’t use water include the use of different-sized rock or boulders, painting the walls different colors, murals, or statuary. Use your imagination or hire someone to work with you who is creative.

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