Xtremehorticulture

Xtremehorticulture of the Desert

Wait Until Very Early Spring to Prune Grapes

1 Comment / when to prune grapes /

Q. Should I cut my grape vines back?  They’re on a trellis, and are 1 year old.  During the summer they spread out very well, and produced several large groups of table grapes.  I’ve attached a photo. A. Regarding your grape vines, I would wait until late February or early March to prune them. We still have some potentially difficult times to go through this winter for grapes. Cutting them early may result in a loss of bud wood and fruit production.             When pruning, you will cut back this past years growth (it will be a different color) so that only one or two buds remain. I prefer two. Also I usually prune it back so that ten or twelve buds remain if I do it early. Then just before bud swelling in the spring (like about early March) I cut then spurs back to two buds. This way if there is dieback during the winter I won’t lose the fruit producing spur.

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Podocarpus Leaf Scorch Update from Previous Question

Leave a Comment / fern pine, how much water do trees use, irrigation, sunburn, sunscald, watering /

Q. Thank you so much for responding to my letter. I did want some clarity on these trees because I was surprised you determined this was a watering and not sunscald. First off, these trees are in a courtyard about 5 ft apart and they are on the same run station.  The trees on the south wall are actually shaded by the wall.  The trees on the north wall are getting more direct sun, so I figured the leaves had sunscald. If you don’t mind my asking, why do you think it’s a watering issue? I clearly diagnosed it incorrectly so I’d like to learn how to better diagnosis this issue if I come across this again. Readers Podocarpus with leaf scorch on the north side.  Podocarpus showing no signs of leaf scorch and with rock mulch, a potential problem in the future. A. I recently started a Yahoo group discussion page because I felt my blog did not give enough opportunities for discussion. It can be found in Yahoo Groups as [email protected] As long as you become a member (which is free but you have to be admitted by the Administrator) you can ask questions, post your thoughts about someone else’s comments or add with your own experiences. It is meant for sharing information. To send a question for my blog you have to send it to me in an e-mail which is [email protected]             It is always difficult to assess a situation remotely. I have to rely on what I know about a particular plant, our climate and soils and my personal experience. I have these plants myself and they are located next to my home on the east side. They get a very small amount of water but it is regularly applied.             First of all, we know they are not true desert plants so we have to add a lot of extra things to get them to grow well here. Soil improvement at planting times is one of them. They will do better with wood surface mulches as well as long as you keep them away from the trunk during the first five years. Besides that, the microclimate or their exposure to the elements can make a difference.             I also know that these plants can suffer if they get watered too often or if they don’t get enough water. The problem is, they look similar if they get watered too often or not enough. When they get watered too often, the roots begin to die. Once the roots begin to die they can’t take up enough water and they look like they are drought stressed. Drought stress will be leaf tip burn like yours or even branch dieback if it is extreme. If it is a chronic lack of water in summer months they usually have leaf tip burn.             I know that plants growing on the north side of the building, or the east side as in my case, are in a cooler location than they are on the South or West sides. High temperatures, wind and lots of sunlight drive plant water use up tremendously. So, plants on the north side and East side will not use as much water as they would on the South and West sides. (As a side note, ideally, we should be irrigating plants on the south and west sides differently than the plants on the north and east sides. This means they should be on different valves.)             You called it sunscald and in a way you are right. Usually the term sunscald has to do with burning of the limbs and trunk of a tree, not the leaves. But that is a technical issue and you would not necessarily know that as a layperson but I got what you meant. We would actually call this leaf scorch or tip burn. Leaf scorch on mockorange             Leaf scorch typically occurs around the margin of the leaf. Leaf scorch occurs because not enough water is being pulled by the roots of the plant and transported to the leaves. The margins of the leaves, or edges, are furthest from the veins and they are the first to show a lack of water, resulting in scorch.             A lack of water can occur because not enough water is applied, or there is root damage so it can’t take up enough water, or the plant is just is not suitable for a very hot and dry climate and it can’t take up enough water in enough volume. We see leaf scorch in plants here like the really big sycamores (that always get cut down when they are about 15 years old because they look so bad) and a few others. Sycamore with leaf scorch due to reflected heat from south facing wall We will also see leaf scorch from plants that are stressed in other ways. For instance, if a plant is suffering in a lack of a nutrient, like iron in iron chlorosis, it will scorch when the same plant which is healthy will not. An unhealthy plant just cannot handle the extremes like a healthy one can. Leaf scorch resulting from iron chlorosis in apricot               Your plants have leaf scorch or the leaves are dying back on the north side but they are doing well on the south side, as you said. I am assuming that the plants on the north and south sides are getting similar amounts of water. If they are good on the south side, then it appears like they can handle that very hot and bright exposure okay (at least for now).             These same plants should have no problem handling a north (less stressful) exposure … but they ARE having trouble. So I ask myself, why do they look poorly on the north side when that should be where they look the best? The reason they look bad on the north side is because of leaf scorch, judging from your picture.             Leaf scorch is a lack

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Be Careful How Close You Plant Figs to Walls

Leave a Comment / now big, planting, pruning figs /

Q. We planted a very small fig tree next to our wall 11 years ago and now it is taking over the whole backyard, I heard the roots can do considerable damage to our plumbing and wall.  20 year old Fig in winter showing form to keep it small and productive A. If the trunk is closer than about several feet I might worry but otherwise I would not unless it is getting its water from your neighbor’s yard. If it is getting a lot of water from your neighbor, then this will pose a problem to your wall in the future.             Always water on the side of a plant away from a wall or foundation. It will not be a problem to water on one side of the plant while not watering on the other. Plant roots will grow where there is water and not grow or grow poorly where there is none or it is limited.             Whenever possible, try to keep soil within 3 feet of a wall or foundation as dry as possible. This helps to reduce problems with roots and corrosion of cement by soil salts.             As a safety precaution you can cut the tree roots on the side toward the wall. Leave the roots exposed to heal a few days and then you can bury them again. Figs in particular can handle severe pruning.

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White Fuzz on Palm Frond Can Be Normal

Leave a Comment / palm disease, palm fungus /

Q. Today I found this frond on the ground and it looks like a fungus on the back of it. Can our palms be saved with treatment? A. From my perspective, there are two options. The first is to recognize that white fuzz on leaf fronds of many of palms is normal. It depends on which palm it is.             My first reaction in seeing the picture you sent was that it was normal and this was one of the palms with fuzz exactly where it is in your picture.             The second option is that it is a disease or insect problem that I have not seen before. We do have mealybugs and scale insects that cause a similar white fuzzy appearance. This normally occurs on palms growing indoors, not outdoors.             I still tend to think that this is a palm with normal white fuzzies on the leaves. What is troubling is that you told me one of your palms died. If the palm is well-suited to our desert climate, death would be rare.             So I went searching for diseases that might give the same appearance as white fuzzies on the leaves. I could not find any.             Many people assume that palm trees are low in water use. They are not. Palms survive very nicely in the desert near an oasis where they can drink freely from available water. They don’t survive in the middle of a desert landscape with a minimum amount of water.             A telltale sign that they are not getting enough water is poor development of the fronds. They may be smaller than normal and scorched around the margins of the leaves. Eventually the bud in the center of the palm dies thus killing the entire palm.             Palms can be weakened if they are not receiving enough water, if they go through a very hard winter which stresses the central Bud, if they are severely pruned to look like a feather duster in late fall or if new palms are planted in the fall instead of spring and summer.             My gut tells me that your palm frond with the white fuzzies is one of the normal palms (you can check this by looking at other fronds on the same plant and see if they are fuzzy as well) and that your one palm which died was weakened and the central bud was killed by bud rot.

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Tricks to Desert Container Gardening: Expanded Edition

1 Comment / failure, problems with, success with /

Q. I was wondering if there is a trick to container gardening. I have been using potting soil, along with plant food, and my plants keep wilting. What am I doing wrong?   A. There are two things you should be aware of regarding watering and containers in our climate. Don’t use small containers and never let the soil get too dry before you irrigate again.             Small containers do not work well in the desert. They just don’t hold enough water and their soil volume is small so it heats up rapidly. Plants use a lot of water in a desert environment. This means they have to draw upon a large reservoir of water in the soil. Large plants in small containers use the water in the soil quickly.             When the soil dries, it shrinks. In containers the soil dries from the outside, inward. The outer surface of this container soil can be very dry or hydrophobic, meaning it will repel water. When the soil shrinks in the container, it pulls from the sides of the container leaving a large crack. The combination of this large crack between a very dry soil and the inside of the container wall makes a nice channel where water can flow. Water applied to dry container soil flows down the inside of the container wall without wetting the soil. Of course you see it run out the bottom and think you have wetted the soil when in fact the hydrophobic soil surface is still dry.             Plant water use can be 25 to 40% higher in our hot, desert climate than in more moderate climates. You have to use larger containers to compensate for this higher water use or water more often.             Another problem. If containers are left exposed to the sun, the soil in the container dries rapidly and can get very hot, sometimes reaching temperatures around 160°F (70°C).             Most plant roots are not as tolerant to heat as aboveground parts. Why should they be? Soil can be a great temperature buffer. Large soil volumes provide a better cushion against high soil temperatures than smaller ones. Also, wet soils are slower to get hot than drier soils so set your irrigations clock to irrigate containers just prior to the heat of the day.             Here are some other suggestions about growing plants in containers in our desert environment. ·       When wetting a very dry container soil, use a couple of teaspoons of liquid detergent in a gallon of irrigation water to help the water penetrate the dry soil. Add the detergent after the bucket is full of water. ·       Always make sure water can drain from the container directly out of the bottom to keep salts moving through the soil profile. Our tap water coming from Lake Mead has lots of salt in it, about 1 ton of salt for every 320,000 gallons (1.28 million liters). ·       When watering, let about 20% of your applied water (1/5 of the volume applied) run out the bottom. This helps flush salts out of the container. This is called a leaching fraction. ·       Replenish container soil regularly. If container plants are annuals such as vegetables, replenish one fourth to one third of the soil volume each time you plant. If the container plant is a perennial such as a fruit tree, remove and replant the tree every 2 to 3 years. When replanting, prune the roots as well as the top to bring it back into scale with the container. ·       Shade the container from direct sun during the day time. You can do this by placing the container inside a larger container. This is called double-potting. ·       Use an inexpensive soil moisture meter made for houseplants to give you a rough idea if the soil is wet or dry. Otherwise lift or push the container. Containers get much lighter when it is time to water. Lift or push it after you finish watering as well. This helps reassure you that the soil is wet. ·       Fertilize lightly once every one to two months during the growing season.

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Italian Cypress Snapping Off in Wind Might be Borers

Leave a Comment / Uncategorized /

Q. Because of the wind the other night the tops of two Italian Cypress trees broke off about 11 feet off the ground. Do you think this was caused by lack of water? We have 18 of these trees by the back fence. We planted them in 2005 and we have been watering them for nine minutes, three times a day, six days a week in summer.             As they grew I didn’t increase the watered until about 3 years ago when I found out they needed more water. So now I use a hose and water each one about 15 minutes every 3 weeks in Summer.  I’m hoping you can see by the picture, there seems to be a growth around the area where it broke off.  Do you think this was caused by lack of water? Italian cypress with possible borer damage. Borer weakened the limb and it snapped easily. A. I can see the picture quite well, thank you. I don’t need to know the watering schedule or amounts. Other people have told me that they think they had borers in Italian cypress. I had never seen borer damage in Italian cypress in my 30 years in Las Vegas.             Well, I think you have it. This growth you are pointing out in the picture, I think is growth we typically see AFTER borer damage has occurred. Borers don’t typically kill a plant overnight, or even in one season, unless the plant is very young and the damage is extensive. Usually plant decline from borer damage can take several years.             Plants can survive and look like nothing is wrong for several years during annual borer attacks. Having borer damage depends on a lot of things; how healthy the plant is, how fast it begins recovery after the attack, how heavily it was attacked, etc.             In short, it is possible that your plants were more susceptible to borer attacks because of a lack of water during the summer.             There is a product for borer control but it would have to be applied once, annually, to protect the trees. It is a good product and you can find it at your local nursery.             In the meantime, if the disproportionate sizes bother you I would go ahead and lower them all so they are the same height. They should do just fine if they are pruned all the same way and I don’t think it will be very noticeable after a season of growth. 25 year old Italian cypress with the top removed

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Plant Podocarpus With Leaf Scorch May Be Too Much Water

4 Comments / brown leaves, fern pine, sunburn, sunscald /

Q. I planted six Podocarpus (Fern Pine) in March, three by the north wall and three by the south wall. Now the three on the north wall have leaves that are turning brown. The three on the south wall are fine. I just didn’t realize that the trees would get this much sunscald.  Any suggestions on what I can do, besides give them macronutrients and hope for the sun to change course? Readers podocarpus with leaf scorch Podocarpus showing very little podocarpus A. Judging from the picture you sent showing the leaves turning brown, I really do not think it’s going to be a continuing problem for you on the north wall once this is corrected. The south wall will be more of a challenge. I do not think this is sunscald but it is either a lack of water, watering too often or a lack of soil improvement at the time of planting.             Since the problem you are having seems to be on the north side and not the south side, I might guess that you are keeping the soil too wet on the north side or they are not getting water.             The north side and the south side are radically different micro-environments. It is much hotter on the south side than the north side. This means plants on the north side should be watered less often than plants on the south side.             Notice that I said less often. The plants on both sides should receive the same amount of water but the difference should be in how often they are watered. To accommodate this difference in frequency of irrigation, plants on the north side should be on a different valve or circuit than plants on the south side.             In the first picture it looks like you have rock for surface mulch. That will be a mistake for these plants in the future. It will be okay for a year or two but you should consider changing this out to wood mulch instead of rock.             If you are going to have problems with this plant, it will be on the south side. These plants will tolerate a little bit of drought and infrequent watering so treat them like landscape trees and shrubs with deep but infrequent waterings.             In other words, do not water them daily. At these temperatures, as long as you have good drainage, twice a week with about 10 gallons for each plant should be adequate on the south side if they are on drip emitters.             On the north side, once a week would be adequate. If they are on drip emitters, they should have an emitter on each side of the plant. Put the emitters towards the front of the plant as far from the foundation as possible.             There is a lot of calcium sulfate or gypsum in our soils. Adding water to soils high in calcium sulfate can increase corrosion on concrete.             After mid-October you can cut your watering to once a week or longer but the same amount of water. In mid-December you can water these about every 10 days.             These are evergreen plants so the damage will not disappear until new growth covers the damage to the leaves.

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Disease Problem Will Stop With a Change in the Weather

Leave a Comment / disease triangle, fungicide /

Q. I am sending you a picture of my funky looking tree. I think it has some sort of disease problem. A Yes, it does look like a disease problem but I think it will stop spreading as soon as the humidity goes back down and rains stop. In fact, this problem most likely occurred a few weeks ago since the new leaves coming out seem unaffected. Plant disease triangle needed for disease to develop .           Diseases need to have three ingredients, all coming together at the same time, to manifest themselves. First, the plant needs to be susceptible to the disease. Plants that are not susceptible or have been bred to be resistant to a disease will not normally get infected.             Secondly, the disease itself needs to be present. This is why I continually ask readers to sanitize their equipment, inspect plants for problems before you buy them and rotate your vegetables.             The third ingredient is the right kind of weather. Most diseases are caused by fungi, the majority of our plant diseases here, and grow and spread under high humidity and rainy weather.             Disease control focuses on interrupting or preventing one of these three ingredients. All we need is a drop in the humidity and it will stop. Also pruning so that you have good air movement through the canopy will also help prevent and reduce its spread.

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Spurge Weed Problem in Lawn Controlled with Fertilizer, Irrigation and Mowing Height

Leave a Comment / mat, spotted spurge, vine, weed /

Q. We have a weed problem in our back lawn and I think it is called spurge. The leaves are small and it’s kind of viney. When I pull it, I see this white sap coming from the broken vines. I can dig it out of the soil where I have gazanias but cannot do the lawn that way. Any advice would be so welcome. A. Yes, that does sound like spurge. Spurge is a poor competitor with other plants. It invades open spots whether you are growing gazanias or a lawn. In open areas surrounding gazanias, the best option you have is to use surface mulch. Mulches can be rock or wood. Gazanias will tolerate both so pick either one. Spotted spurge leaf closeup also showing white latex coming from freshly broken stem             Actually your lawn is acting like living mulch. As long as you keep your lawn a solid covering and healthy, it will be difficult for any weed to invade.             Make sure your mowing height is high enough to shade the soil surface. Weed seeds like to see light if they are to germinate and invade. Secondly, fertilize your lawn regularly to maintain its density. Fertilizers that help to maintain its leaf density and shading of the soil will be high in nitrogen.             Thirdly, make sure your sprinkler system covers the entire lawn with water as evenly as possible. Most homeowners do not understand how to design a good sprinkler irrigation system. If you are going to design it yourself, make sure you learn how to do it correctly and don’t just assume you know what you’re doing.             Any weakness in the irrigation system will result in brown patches, dead spots in the lawn and invasion by weeds.             Make sure your sprinklers pop up high enough so they throw water from above the top of the grass. For heaven’s sake do not use 2 inch pop-ups unless you have bermudagrass. Do not trim around your 2 inch pop-ups because they are too low or you definitely will see weed invasion in the lawn.

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Bougainvillea with Leaf Damage in Circles

Leave a Comment / circles in leaves, leaf cutter, leaf damage /

Q. I bought a Bougainvillea (‘Barbara Karst’) last April and planted it in my front yard. After digging the hole I added a local Rose and Flower food in the bottom of the hole. I then added water and then planted the Bougainvillea.             This plant receives sunlight more than 6 hours every day and I water it as noted on the label. All went well until something started to carve big divots out of the leaves. I sprayed “Ortho Bug B Gone” as I was told and only sprayed it on the plant at night so it would not burn the leaves.             Well it did the trick but the edges of the plant started to turn brown and shrivel up. As soon as new fresh, unsprayed tender leaves came out, the bug came back and started to carve out holes in the leaves again. Is there something I am doing wrong? ‘Barbara Karst’ Bougainvillea with Leaf cutter bee damage in flowers A. This is the leafcutter bee and the female is using your bougainvillea leaves to build its nests. These bugs are good guys and help to pollinate our fruits and vegetables. By the way, these bees are very docile, only sting if they are provoked, and cannot become Africanized.             I never recommend spraying to control bees of any kind. I tell people to “live with them” and encourage watering and fertilizing to encourage more growth.             Add plant more to lessen the damage on individual plants or plant other plants to lessen the visual damage. These include roses, many kinds of flowers, grapes and basil.             The damage will not hurt your plant if you can live with it. I will put more information and pictures on my blog several months ago. In the blog search engine, type in “leafcutter bee”.

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