Xtremehorticulture

Xtremehorticulture of the Desert

Pine Tree Recovery from the Heat

Leave a Comment / drought, heat, irrigation of trees and shrubs, pine, Super Thrive, vitamins, watering /

Q. I have fifteen-year-old, 20 to 30 foot pines on a half-acre. They suffered during the heat this past summer. After your advice, I am doubling the amount of water and hosing off the needles once a week. How long is the recovery time using vitamins?    Too much water? Probably not. But they don’t need it as often as a lawn does. When you look at the amount of water that pine trees need, the total amount of water is not far from what an efficient lawn would need. The difference is in frequency of application. Trees, this includes pine trees, should be watered much less often than a shallow rooted lawn. A. I am not a big fan of applying vitamins like Super Thrive. Some people swear by them, It can be cheap insurance though if you’re not sure. Your call on that one. Who can argue with success? The research doesn’t support it but the use of products like these (and other “me too” products) are not supported by research. However, some landscape professionals and homeowners disagree. In the long run, it’s cheap insurance to use it.             Washing the needles of pines is not necessary. It is true of Italian cypress because they tend to get spider mites. Pines do not.             They might need more water than 15 gallons. Play that by ear by watching the new growth next spring and early summer. You should get at least 12 inches of new growth every year and not experience severe needle drop during the hot months. Those are indicators the tree is not getting enough water. When you see this in a pine tree growing in the desert, it usually means a lack of water. The amount of water pine trees need is grossly underestimated by most homeowners and landscape professionals. They need a lot of water all at once but they don’t need it that often.             Once you find the right amount of water (minutes and gallons), keep it consistent through the year. The amount of water they are given should not change much throughout the year. It’s like filling a gas tank. Instead, change how often they receive the water. Summer months water more often. Winter months, water less often. One of the best ways to irrigate large trees is to “basin irrigate”. This is a modification of an irrigation technique called “flooding”. Rather than drip irrigation, a landscape bubbler (not a drip bubbler) is used to fill a flat basin. The basin around the tree, doughnut if you will or moat, must be flat! This basin is increased in size every few years to accommodate a larger tree. The bubbler emits water at one or 2 gallons per minute. The basin is full in 10 to 15 minutes.             As plants get bigger, they require more applied water, not watering more often. Watering frequently with small amounts of water produces shallow roots and trees that blow over in strong winds.             You should see an improvement in the first half of next year. Nothing this year.

Pine Tree Recovery from the Heat Read More »

Bermudagrass Lawn Change of Color May Be Drought

Leave a Comment / brown patches, dead areas, drought, grayish green, irrigation, lawn, turfgrass /

Q. We have lived in the same house in Las Vegas for the last 42 years and every June my lawn has the same problem. The lawn is a mix of common and hybrid Bermudagrass. First the grass turns grayish (in patches) and then it turns brown. It slowly comes back by September. I water according to local recommendations, use Scott’s Turf builder 3 to 4 times a year and use Ortho Bug-B-Gone insect granules twice a year.   A. If this were tall fescue I might be tempted to say this is a disease problem. However, since it is a mixture of Bermudagrasses I think this is an irrigation problem. This will be particularly true if these problem areas are in the same locations every year. Turfgrass or lawns will turn a smoky or grayish green when they are not getting enough water. This is because the leaf blade either folds in half or roles depending on the grass. This creates a different color; smoky or grayish green             Bermudagrass in our climate doesn’t develop many insect or disease problems.             The success of lawns in our desert climate is directly tied to the quality of an irrigation system. In technical terms we say the irrigation system should provide head to head coverage; water from a sprinkler head should be thrown far enough to reach the head to its right and it’s left. If we don’t provide this kind of uniformity in the design and installation of an irrigation system it can result in brown patches that don’t receive enough water. A close-up of the grayish green color where the lawn is not getting enough water             The water pressure in the sprinkler system should fall within a range recommended by the sprinkler manufacturer. If the water pressure is too high or too low it will affect the distribution of water and create browning of the lawn in the same areas year after year. Otherwise, there are sprinklers now that will lower the water pressure before the water is applied to the lawn. Another indicator of drought or lack of water in a lawn are footprints. If you walk across grass that needs water, look behind you. If your footprints remain in the grass does not spring back quickly, the grass needs water.             You can correct this problem in the short run by increasing the number of minutes that you apply water. This delivers more water to the dry areas. Unfortunately, it also delivers more water to the wet areas resulting in overwatering of the green areas.             It is also a good idea to punch holes in the lawn with an aerating machine in the spring, particularly in the brown areas. This helps water to move into the soil and not run off into low spots if there are any.             Bermudagrass is notorious for building up “thatch”. Thatch is a buildup of old grass stems and debris under the surface of the lawn but on top of the soil. Years ago this thatch was burned off of the lawn with fire. We can’t do that anymore. We must do it mechanically now. A core aerifier for lawns pulls plugs or cores out of the lawn that are about 4 inches deep. This type of verification provides better drainage and water penetration for lawns suffering from drought             It is important to dethatch Bermudagrass each year. This is usually done in the fall when overseeding it with a cool season grass like ryegrass to maintain a green winter lawn. If the lawn is not overseeded in the fall then thatch can be a huge problem in Bermudagrass. D thatching machines, sometimes called vertical mowers, pull debris from a lawn which allows water to better penetrate the soil and reduces runoff.             Making changes to the irrigation system will correct some of this problem and reduce the amount of water needed to keep the lawn green. Increasing the number of minutes you apply water during the heat of the summer should solve this problem in the short run.             But I would combine this with lawn aerification every three or four years and dethatching every year to improve the amount of water entering the soil in the dry areas.

Bermudagrass Lawn Change of Color May Be Drought Read More »

Correcting Oleanders with Leaves Browning Along the Edges

Leave a Comment / drought, Oleander leaf scorch, over watering, salinity /

Q. We have one oleander approximately 2 years old and 4 new ones we purchased several weeks ago.  The older one (1st photo) and one of the new ones (2nd photo) have some leaves that are browning along the edges while the centers are still green; a few have tips that are browning too.  From what I’ve read, could the plants have leaf scorch or, “salt or boron toxicity”? Two pictures sent in regarding oleander leaf scorch A. You are right, this browning along the margin of oleander leaves, or leaf scorch as it is sometimes called, could result from a number of things. One possibility is a bacterial disease that has been called Oleander Leaf Scorch. It is a bacterial disease which is rarer in plants than fungal diseases. This disease is carried from plant to plant by what we call “vectors”. These vectors can be insects that feed on the “juices” of this plant or they can be transmitted by humans on pruning shears. This is why I am constantly reminding people to clean and disinfect their pruning equipment before they begin pruning and between plants if the plant they finished pruning appears to be “sick”. More information about oleander leaf scorch from the University of California Leaf scorch can also because to buy a lack of water and excessive salts in the soil which can be made worse if plants do not get enough water. One particular salt that you have identified as a problem in our soils is boron. The other particularly troublesome salts contain sodium and chlorides. Salts that contain for plants, such as nitrogen, phosphorus, potassium and others can also cause leaf scorch if they are in excess. Fertilizer salts containing high levels of nitrogen can be particularly troublesome and cause plant damage if applied in excess, too close to the plant or when soils are dry. What to do? Apply compost around the base of the plant and either wash it into the soil or lightly dig it into the upper surface of the soil. Add more water. If you feel as if the plant is not receiving enough water, add more drip emitters. This is preferable to just increasing the number of minutes since everything watered by that valve will be affected. If you’re fertilizing the plants, make sure the fertilizer salts that you apply are kept at least 12 inches from the trunk and applied near the emitters or bubbler. Make sure the soil does not become dry between irrigations because dry soils increase the concentration of salts already in the soil. Lastly, cut the oleanders to the ground and let them re-grow from the base. If you apply more water, improve the soil and are careful with fertilizers and the plants still have leaf scorch during the next growing season, then dispose of them and to get new ones. Oleander leaf scorch will not be in the soil. It can only be transmitted from unhealthy plants to healthy plants either by insects or humans who are not careful about pruning.

Correcting Oleanders with Leaves Browning Along the Edges Read More »

Turfgrass Dead Spots. Irrigation Problem?

Leave a Comment / brown spots, drought, irrigation, sprinkler problem, watering problem /

Brown spots or dead areas in lawns can be common during summer months. It might be a disease, but then again, it could be something else. There is a sprinkler head in the center of the green spots. The three primary reasons that lawns develop brown spots or dead areas are due to irrigation problems, the development of diseases and insect damage. Irrigation Problems. How many times have I heard, “I know the sprinkler system was installed right. I did it myself.” Just because you did it yourself, does NOT mean it was done correctly. If it was done correctly did you design it for “head to head” coverage? Did you size your pipe taking into account all of your nozzles gpm and friction losses? Did you make sure the pressure of your  First sign of an irrigation problem is that smokey-grey color in your lawn when it gets hot. system falls within the manufacturers recommended pressure range for your nozzles? I can go on. If you understood these terms and took them into account then maybe you did it right. Pressure too high. Sprinkler in the center of that little green spot of grass Any weaknesses in your sprinkler system will show up when temperatures hit 110F and 15% humidity. Lawn water use will exceed 4/10 of an inch of water every day. The first thing you will notice when temperatures start to get hot are smoky-grey patches start to show up in your lawn. Then the brown spots or patches start to appear and they are often not clearly defined. Oftentimes they are smack dab between the irrigation heads when heads are not spaced appropriately, nozzles are mismatched, heads are not perpendicular to the lawn or you use 2 inch popups when you should use 4 inch. Sometimes these brown patches can be right next to the head if the pressure of your system is too high and the sprinklers “fog”. In order to clear up the problem or you use the wrong type of nozzles. Little bit of drought and disease mixed in this lawn. ·       Know the operating pressure of your sprinkler system. ·       If mowing at two inches or above use four inch popup sprinklers. ·       Space sprinkler heads and select the right nozzles to provide head to head coverage (water from one nozzle should reach the neighboring nozzle and vice versa). ·       Size irrigation pipe to provide water flow through the pipe not to exceed 7 feet per second when operating. ·       Use a system pressure regulator (if operating pressure is to high) or a booster pump (if operating pressure is too low) so that operating pressure falls within pressure range recommended by sprinkler nozzle manufacturers.

Turfgrass Dead Spots. Irrigation Problem? Read More »

Vitex Water Management Affects Blooms and Growth

14 Comments / drought, lack of water, no flowers, thin canopy, too much water, vitex /

Q. I have a Chaste tree that has been growing in my backyard for about seven years.  The branches have always been full of leaves and I would get an abundance of beautiful purple blooms. Last spring, I noticed there were not as many leaves and I would only get purple flowers here and there. This spring again the leaves are sparse and the branches are mostly bare. Should I be doing something extra to bring back the lushness of my Chaste tree? A. Vitex, or chaste tree, is relatively pest free. It originates from the Mediterranean region where the summers are usually hot and dry and the winters cool to cold and wet. Vitex in winter             The only real problems the plant has are if the roots remain too wet or the plant doesn’t get enough water. So my reaction to your question was concern about your irrigation practices; either watering it too often or not giving it enough water when you do irrigate.             Both could cause similar problems. If the roots stay too wet, root rots develop and you might see a thinning of the canopy and branches dying back. Watering too often results in poor growth or worse. If overwatering continues, you would probably see dieback in the tree and eventual death from root rots.             If the plant does not receive enough water, the plant canopy will begin to thin out and along with that a reduction in blooms.  If you feel like this tree does not get much water then try flooding the area around the tree once a week in conjunction with your irrigations. If the problem is not enough water, you should see a reaction to additional applied water in 3 to 4 weeks. Vitex in bloom             It also will do best with irrigations similar to other most of your landscape or fruit trees. This means regular deep irrigations.             Avoid daily irrigations. Water about twice a week during the hot summer months. In the spring and fall months, water deeply and thoroughly once in a week. As temperatures cool towards winter, you would probably irrigate deeply every 10 to 14 days.

Vitex Water Management Affects Blooms and Growth Read More »

Japanese Blueberry With Orange Leaves a Sign of Leaf Death

Leave a Comment / drought, japanese blueberry, Las Vegas, leaf death, leaf pigments /

Q. My water accidently turned off for two weeks and my Japanese Blueberries are all orange. I do see new growth on the edge of the branches. Is the tree shedding old leaves? Did the cold snap in November cause this? Orange leaves on Japanese blueberry as they are dying and falling off. A. The orange color is the color of the natural pigments in the leaf as the leaf dies, its green chlorophyll disappears and leaves behind these orange or reddish pigments. These colors are typical of anthocyanins and related biochemicals. It is hard to say “after the fact” on something like this. All you can really say is that the leaves have died and will fall off. Now the question is whether “the death” went further than this or not. So you would normally take hold of the branches with dying leaves and bend them. If they are supple and the leaves drop then it was a recent “trauma” to the plant and you cannot be sure yet if the death is going further or not until you see new growth. You can be pre-emptive and cut these branches back and force new growth or wait, your call. The fact you are seeing new growth is very positive. You realize that Japanese blueberry is not the best choice for a carefree landscape in Las Vegas. It is best planted in a part of the yard protected from late afternoon sun and it will definitely not do well in a rock landscape.

Japanese Blueberry With Orange Leaves a Sign of Leaf Death Read More »

Eliminating Lawn Can Lead to Problems for Established Trees

Leave a Comment / convert from lawn to desert landscaping, desert landscape, desert landscaping, drought, retrofitting landscape, xeriscape /

Q. I have a beautiful Loquat tree where the leaves have suddenly started to turn yellow and fell off.   Most of the fruit has also fallen off. The tree was located in the middle of grass. I had the landscape converted to desert rock in September. At the same time watering schedule was changed. I suspect it is being under watered. But before I increase it I want to ask if the cold winter we had here could have caused this yellowing. A. Thanks for the pictures. It is probably not the cold. In a lawn situation the roots go everywhere and anywhere and usually spread to about 1½ to 2 times its height away from the trunk. Loquat with rock mulch applied after growing in a lawn for a few years. In many cases the drip emitters do not apply the water in the same places as lawn irrigation and the plant roots of established trees and shrubs die back. This results in leaf drop and eventual die back of the limbs of established trees and shrubs.             In drip irrigation we usually place the emitters a foot or so from the trunk. This bypasses about 80% of the root system it created when growing under a lawn.             So, yes, it probably is drought but perhaps not because you are not delivering enough water. It is more likely that most of the tree roots are not receiving water. You can place emitters over a greater area under the canopy of the tree. But I would also reduce the size of the root system.             Try root pruning the tree to reduce the size of the root system so it is closer to the emitters. Keep tree roots contained in the area directly under the canopy. Wet the soil thoroughly under the canopy and vertically slice the roots in a circle all around the tree at the edge of the canopy. This can be done with a sharpened spade. Leaf drop of established loquat due to replacement of lawn with rock mulch and drip irrigation.             At the same time, thin the canopy by removing wood. This reduces the tree’s demand for water. A tree that size will probably require 20 to 30 gallons each time you water. With the lawn now gone, the tree will actually use more water since the cooling capacity of the lawn has been removed.

Eliminating Lawn Can Lead to Problems for Established Trees Read More »

Oleanders Drop Leaves in Drought. Will it Recover?

Leave a Comment / drought, drought resistance, leaf drop, leaf scorch, oleander /

Q. I read the post on your blog on oleanders with interest. I too have an issue. My five oleanders are mature (at least 20 years old) trees.  When we moved here a year ago they had not been watered.   When the water was turned on and major landscaping installed, many of the leaves turned yellow and dropped. However the trees blossomed and continued to do fine.  This is not the readers oleander but this oleander has leaf scorch and leaf drop while the oleander behind it is doing very well. Check the emitters or the source of water. This is a good sign it is getting a lack of water.             During the rains the gardener turned off the water system and sadly forgot to turn it back on. The water is of course back on but I have had to replace many bushes, although NOT the oleanders.  However they have begun to turn yellow again and are dropping leaves. There are still a majority of green leaves and the trees are about to burst into blooms. They have been fertilized, as has everything on the property, but I am baffled.  Would you be so kind as to give me your advice on what is happening and why? A. Oleanders are so extensive worldwide that no one is sure where they originated from. Their climate of origin is important because it determines under what conditions these plants perform best but we do know quite a bit about how oleanders behave with and without water.             We know that they are very drought tolerant. This means that when there is limited water, they can survive. Many plants can’t do this. Normally when drought tolerant plants first experience a lack of water the leaves will drop and the canopy will become sparse. If the water continues to be sparse the leaves they produce will be few and smaller and little new growth. They have to have a sparse canopy to survive.             However when water is present they have the potential for using a large amount of water and are not low water users. They respond to this water by growing more, setting new leaves that are quite a bit larger and shedding the old ones. The plant itself becomes denser and flowers profusely (provided they are not trimmed with a hedge shears).             Leaf drop is very characteristic in response to a drought. It is also characteristic when they receive water again after a drought. It is also characteristic of older growth to shed some leaves on older wood.             So, in a nutshell, going from drought to abundant water expect some leaf drop. And when oleander grows normally, expect some leaf drop as the plant matures but not typically as much as during dry/wet periods. So is oleander a good pool plant? No.

Oleanders Drop Leaves in Drought. Will it Recover? Read More »

One of Several Pine Trees Sparse and Scrawny

Leave a Comment / brown needles, circling roots, disease, drought /

Q. Why does my one pine tree seem so sparse and inadequate?  I purchased four Mondale pines and treat them all equally. But one of them looks so scrawny.  The other one shown looks healthy and appears to be robust.  Any thoughts on that?  A. The usual reason for a pine tree being sparse and not full is that it is not receiving the same treatment as the others. Pine trees generally maintain needles on their branches until the wood gets to be three to five years old and then the needles are dropped from the older wood. This older branch is needle-less except for small branches growing from it less than five years old.             The reason for canopy thinning is the loss of needles at a higher rate than they are being replaced. So bottom line for a pine tree becoming sparse is that the tree is not putting on enough new growth. Reasons for this include a lack of water, fertilizer, damage to the tree, or less likely, diseases or insects. Pine needle brown dieback due to lack of water             By far the most common reason is that the amount of applied water is not enough. So when you say you treat them the same it does not necessarily mean these treatments are all reaching the trees equally. But if there is inadequate water two things will happen; the tree will put on less growth and the needles will begin dying back from the tips.             The first thing to do is to check and make sure that whatever is delivering water to the tree is not plugged. Secondly, make sure that water is not running off the surface to some other location. Just because water is applied to a tree does not mean it is getting to the roots. Circling roots of semi mature tree due to circling roots in the containers             Remember, that as trees get bigger their demand for water increases. The increase is not simply a few gallons per year but is much greater because trees are three dimensional in their water use unlike a lawn. Unlike a lawn, when a tree doubles in size its need for water more than doubles.             The next most common reason is that the roots of the tree never fully established into the surrounding soil after planting. This can be because the tree was too old for the container and the roots started circling and never established into the landscape successfully.             It can also be because the tree was not firmly staked at the time of planting. Correctly staking a tree will immobilize the roots and help them to establish successfully into the surrounding soil. You should be able to push on the trunk and NOT see any movement of soil at the base of the trunk.               The next most common reason is damage to the roots or trunk. This will be far less likely than a watering problem but much easier to identify. This can be physical damage like construction, damage from chemicals like salts or weed killers, insect or diseases like collar rot.             If the tree is being shaded by other plants and not receiving enough light (at least six hours a day) then these branches in the shade can drop their needles. If this is the case then some pruning to allow more light will help. If they are planted too close together then consider removing trees so the remaining trees will thrive.

One of Several Pine Trees Sparse and Scrawny Read More »