Xtremehorticulture

Xtremehorticulture of the Desert

Leaf Drop Can Harbor Insects, Disease

1 Comment / cleanup, leaf drop, sanitation /

Q. Is it best to remove all the leaves from the soil after they have fallen or leave them on the soil as mulch for fruit trees? My concern is about insects that might stay there during the winter and cause damage in the spring. fr From reader A. In a very general sense I have two concerns regarding leaving undecomposed leaves at the base of plants. You are right, the first one is insect problems and it’s very possible some insects will overwinter under loose leaves that have not decomposed.             Remember to pick up any fruit lying on the ground as well. Do not leave dried fruit on fruit trees because of potential insect problems.             One insect in particular is the grape leaf skeletonizer. Don’t leave debris around the base of grape plants because of this insect problem. Make sure leaves are shredded or composted. If you have one, lawnmowers are efficient leaf shredders. The second potential problem is disease. There are a few diseases that cut overwinter on fallen leaves. It is always better to compost or shred leaves if you’re going to leave them around the base of plants. Sanitation in the garden is important.

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Fungus Gnats Problem in Potting Soils

1 Comment / fungus gnat control /

Q. It seems no matter what brand of potting soil, I have to bake it before I can use it. If I don’t, I get hundreds of tiny flies that hatch and swarm. I put out water to catch and drown them. I spray insect oil on top of the soil several times a day. I’m so afraid I’ll kill the plants. A. Yes, fungus gnats in particular are a big problem in potting soils used for houseplants. The younger generations feed off of both decaying plants and soft, succulent living roots. They aren’t very particular about what they feed on, living or dead, so long as it is soft, juicy and tender. If fungus gnats are extremely happy in their environment they will multiply very rapidly and cause poor growth and stunting. Besides, they are pesky and a nuisance inside the house. If potting soil is sterilized by the manufacturer using a heat treatment it should kill all of the fungus gnats and should pose no problem. Control fungus gnats with organic pest control products such as beneficial nematodes that go after their destructive larvae and a bacterium is also available with a similar result. You should be able to find these products in your local nursery or garden center. Yellow or blue sticky traps also work. I received this video on how to make yellow sticky traps from a friend. Another effective method is to sterilize this potting soil yourself by placing it, moistened, into a clear plastic bag and let it bake in the sun. Temperatures need to get up to about 160 F for at least 30 minutes for good control. Another option is to apply pyrethrin sprays to the soil and water it in. More information about fungus gnats from the University of California

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Am I Applying Too Much Nitrogen?

Leave a Comment / nitrogen fertilizer, plant tonics /

Q. We fertilize all of our bushes early spring and mid fall with a 5-10-5 liquid plant tonic.  Hopefully this isn’t too much nitrogen. This concentrated fertilizer  has no nitrogen but very high percentages of phosphorus and potassium A. There are two ways to look at this question. Applying too much nitrogen can mean either applying it too often or applying too much in a single application. If you follow label directions, the amount of nitrogen applied should be correct. Apply nitrogen as often as 8 weeks apart if you want continuous growth.              Applying excessive amounts of nitrogen can damage plants or cause excessive growth of leaves and stems.             When judging how much fertilizer to apply and how often, observe the plant. If the plant does not have good growth or the flower size and numbers have diminished, apply fertilizers or “plant tonics” if you prefer. Applying too much nitrogen, the first number, is not normally a long-term problem. The potential long-term problem involves the over application of the second or middle number, phosphorus.  Phosphorus stays bound in many soils for much longer periods of time than nitrogen. Apply fertilizers containing high levels of phosphorus (middle number) less often than fertilizers that contain high levels of nitrogen. As a general rule of thumb, apply fertilizers containing phosphorus once a year to established plants, two weeks before flowering. The rest of the time use high nitrogen fertilizers. The exception is at planting time. Every time seed or transplants go in the ground, apply a high phosphorus fertilizer. Before planting, mix high phosphorus fertilizers in the soil to the same depth the roots will grow. Bagged compost can be hard to find. Most bagged products that contain compost are soil mixes, not straight compost. Consider using compost instead of a mineral fertilizer. I am talking about compost which is harder to find, not a soil mix that contains compost. Most composts have a good balance of nitrogen, phosphorus and potassium and can be used as a substitute for mineral fertilizers. Composts provide plants with a lot of minor elements not found in mineral fertilizers. Compost lowers soil alkalinity, stimulates good soil microorganisms and provides humus or “black gold” to the soil. It is a very powerful addition to desert soils.

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Some Houseplants Need Their Roots Pruned

Leave a Comment / propagation, root pruning, root to shoot ratio /

Q. We repotted a house plant that was constantly wilting and that seems to help. Is it possible that the plant is too large and needs a “haircut”? A. Potted plants benefit from root pruning as well as top pruning if it is possible to do so. I guess we could call this a “haircut”. Both the top of the plant and its roots should be “in balance” with each other. We sometimes refer to this as a plant’s “root to shoot ratio”.             More about root to shoot ratios Not all plants can be root pruned and top pruned to make them smaller so they perform better in their container. Some plants will need a larger container. Some plants are made smaller by “dividing” the plants. Plants that require division are removed from their container and separating a “clump” of plants into individual plants with a sharp, sanitized knife or pruning saw. The cut ends are dipped into a fungicide before replanting. Some plants require renewal through propagation. Typically these plants are propagated using methods such as stem cuttings, leaf cuttings, root cuttings or layering. These specialized propagation techniques are specific to certain plants. The Internet is a good source of information on propagating interior or houseplants. Propagation of Houseplants

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Pruning Roots of Plants Gives Added Control

Leave a Comment / root pruning /

Did you know that the roots of plants can be pruned? This is called root pruning and dramatically alters the root to shoot ratio of plants. Root pruning, what is it? As the name suggests, root pruning is the cutting of roots. It is done for different reasons than pruning the tops of plants. We have total access to the tops of plants. Axis to the roots of plants is much more limited. Roots grow differently from stems. Roots do not have buds. You can virtually cut anywhere on a root and it will “sucker” unlike many of the stems of trees and shrubs. Why root prune? The most common reasons for root pruning include controlling the size of the plant, slowing the growth of plants, initiate flowering, keep the roots closer to the trunk, keep the roots out of problem areas or creating problems. This is a root pruning machine used in nursery practices for undercutting trees growing in the field under production.This machine is driven so that the young trees are undamaged as they pass under and between the tracks. The U-shaped blade is pulled behind this machine and undercuts the roots…root pruning… to make a bare root fruit tree that will transplant to the field with fewer losses. Photo taken by me at Dave Wilson Nursery www.davewilson.com  Root pruning is commonly done in the nursery operations where trees and shrubs are grown to be transported for planting in a new location. Root pruning is common in bonsai to reduce the growth of plants and keep them small. Root pruning is done in some greenhouse operations for similar reasons to nursery operations. If root pruning is not done and the top of the plant dies or is severely pruned back, then the top regrows again very quickly to its original size. Once it reaches this size, growth slows again. This is the plants way of reestablishing what we have called the root to shoot ratio of the plant. The plant “recognizes” the difference in size between the top growth and undisturbed root size. The plant directs its growth, the flow of carbohydrates and hormones, to the top of the plant at the expense of growth in the roots. How can I use Root to shoot ratios? If a plant is growing too rapidly and you want to slow it down, root prune it. Take a sharp shovel and sever the roots by pushing it through the soil and through the roots as deep as possible. Do you want to keep the roots of plants from entering the septic tank or other problem areas? Root prune between the plant and the problem area. Root prune every 2 to 3 years. Some diseases are transmitted from plant to plant when the roots fused together and what are called “root grafts”. This commonly occurred in American elm with the transmission of Dutch elm disease. Root pruning can isolate plants from trees that are carrying the disease. If an Apple or Pear tree dies from fire blight, root prune the area around the dead tree to prevent the transmission of the disease through root grafts. When Retrofitting trees and shrubs from a lawn area to drip irrigation, consider root pruning these trees and shrubs to generate roots closer to the trunk were the emitters are placed. Having trouble with the tree flowering? Try root pruning to create a new root to shoot ratio that might slow the top growth and induce flowering.

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How Many Days between Waterings in the Winter?

Leave a Comment / how often to irrigate in the winter, Watering during the winter /

Q. I am not sure how long some of my trees can go without water during the winter. I have a mature Pepper, Mesquite and some palms that I have not watered for 10 days because of the cold temperatures. Is 10 days between watering okay? A. 10 days between waterings should be no problem for trees and large shrubs provided they were given a deep watering prior to this. Deep rooted plants, like most trees and large shrubs, can go without water for a longer period of time than smaller plants. Deep watering means flooding the soil with water to a depth of 2 to 3 feet. If drip is used then making sure enough volume of water is applied to soak to a depth of 2 to 3 feet. Applying water with drip emitters this close to the trunk is okay for the first couple of years. As this tree gets larger, more emitters will be placed underneath the canopy of this tree and further from the trunk. About half the area under the canopy should receive water. Apply enough water in a single application to wet the soil to a depth of 2 to 3 feet. Many landscapes have small plants and big plants on the same circuit or valve. This means the small plants cannot be watered separately from the larger plants. The small plants require water more often. This forces the larger plants to be watered frequently even when they don’t require it.  This twisted Acacia would be considered a desert tree. Putting a tree like this on an irrigation circuitFor desert plants gives greater flexibility when applying water. Applying water more often causes it to grow faster, larger and more dense. Applying water less often keeps it smaller, growing more slowly with fewer leaves. Secondly, plants that do not originally grow in desert climates must be watered more often than plants which do. The mesquite and California pepper are both desert-type trees where water can be withheld for long periods of time with no problems. Palms are more shallow rooted and require water more often. But ten days is not too long for any of these plants during the winter. In an ideal world the deeper rooted plants would be on a separate irrigation circuit or valve from shallow rooted plants. Deep rooted desert plants like acacia, palo verde and mesquite would be on a separate circuit from the other non desert deep rooted trees and shrubs. This gives you alot of flexibility in watering.  Palo Verde is another desert tree whose growth can be managed by applying more or less water. Putting desert trees and shrubs on their own separate irrigation circuit gives you this type of flexibility. The deep rooted plants would include trees and shrubs and deep-rooted woody perennials that die back each year such as Bougainvillea. The shallow rooted plants would include annuals and flowering perennials that die back each year like Lantana. Lawns should be on a separate circuit but could be tied into vegetables as long as the water could be turned off to vegetables between seasonal plantings. 

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When to Harvest Oranges?

Leave a Comment / When to harvest oranges /

Q. My oranges are turning orange. How long should I wait before I harvest them. Yes, oranges and other tender citrus will grow in Las Vegas but not without some careful considerations. A. Oranges do not necessarily turn orange before they are ready. Orange color develops due to climate. In the tropics oranges remain green or green/yellow even when  they are ready to eat. Fully ripe oranges in the Philippines. They do not turn orange because of the warm climate. The fruit above it is rambutan. Orange color is induced in oranges that don’t develop good color using ethylene gas in closed rooms where orange color is important for marketing and sales. The best way is to pick one and try it. If sufficiently sweet, harvest the others or wait and harvest when needed during cold months but leaving them on the tree too long can reduce the number of flowers in the next cycle of fruit production. When they are ripe start removing them. Cut the stem close to the fruit, don’t pull the fruit from the tree, for better storage life. Handheld refractometer used for measuring total dissolved solids (sugar content) from the juice of fruits and vegetables. A sophisticated method is to purchase a small handheld device called a refractometer and measure the sugar content. Maturity in fruit is usually a measure of the sugar content which the refractometer will read for you.

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How Often to Water Fruit Trees in the Winter?

Leave a Comment / irrigation schedule winter, Watering fruit trees in the winter /

Q. Do you have any guidelines for watering fruit trees in the winter?  I cant find anything specific to winter watering on your web page. I have apricot, nectarine, apple, fig, pear, plum, cherry, peach, orange – planted spring 2015.  I am not expecting the apple or cherry to make any fruit yet, They are just ornamental. Pomegranite, jujube, lime, grapefruit I planted 3 years ago. Will deep watering once a month suffice for December – February? Fruit tree with irrigation basin surrounding the trunk. Irrigation bubbler at the top right of the basin that allows 2 gallons of water to flow from it every minute. The basin must be level so that water flows evenly across its surface.Surrounding the trunk is rabbit protection. A. Once a month is not even often enough for trees established for years in our warm winter desert climate. Once they have been established, trees established for one season might be closer to every two weeks during the winter. If the soil is very sandy, then once a week. Fruit trees surrounded by dry soils should be watered more often than trees in wet soils. Wet soils in the desert might happen if fruit trees are grown close to a lawn area, a wall that has irrigation applied on the other side of it, intercropped between the trees with other plants like vegetables or herbs. Irrigation basins surrounding newly planted fruit trees that have been staked and mulched with wood chips. The screening around the trees is for rabbit protection which also keeps the wood mulch away from the trunk. If drip emitters were used, two emitters might be enough for the first 2 to 3 years. When they have reached 2 to 3 years old than increase the number of emitters to at least four. Generally speaking, if there is a surface mulch of at least three inches, add one to two days in the summer and up to one week in the winter. Sandy soils require more frequent watering with smaller amounts applied. Desert soils should contain 50% compost at the time of planting. Fruit trees perform much better with wood mulches applied to the surface and require less frequent watering. General Watering Schedule for Fruit Trees Let me run down a general schedule of watering fruit trees that is ignoring rainfall since we only receive an average of 4 inches (10cm) or rain each year. Newly planted in spring or fall during cool weather….2-3 days; winter 1 to 2 weeks depending on soil and mulch covering. After growing for one season then assume the trees are established. Fruit trees established at least one season with fruit or nuts on the tree… Summer every three to four days depending on soil and mulch. Spring and fall, weekly. Winter every two weeks. Fruit trees that have been harvested can be watered less often.

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