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Sunday, December 7, 2014

Pruning Oleander Correctly Is Very Simple

Q. I purchased dwarf oleanders two years ago in five gallon containers. They are doing fine but are about four feet high. It is my understanding the plants can be pruned. I need to know the best time to do so and how far down to go without harming them.

A. Pruning oleander is very simple, much simpler than many other plants. You can prune them any time of the year without any problems. Having said that, they are usually pruned during the winter, late winter or very early spring.

Prune them with a loppers; the one that has two handles and you have to use both hands. Count the number of main stems coming from the base of the plant. Identify the two or three that are the oldest. They will be the largest in diameter.

 Remove these oldest ones within a couple of inches above the soil. You are done for this year! It takes about ten minutes and no mess to clean up! If there are some unusually long ones remove them from the base as well.

Repeat this about two or three years later. Continue this cycle of removing the largest diameter every three years or so.

Please do not use any hedge shears unless you don’t like the flowers. Having said all this, the absolute best time to do this in southern Nevada is February but you can do it any time without damaging the plant!

Euonymus Plants Have White Spots and Dying

Q.My euonymus plants are dying. These are all plants that have been in the ground 8-10 years. Now, they are getting a white spot on their leaves and shortly afterwards the plants die. The plants in my backyard did this last year, and now plants in the front have the same symptoms. Some people said they needed more water. That didn't do anything for the white spot. I tried cutting off the spotted leaves. That might help, but I am not sure. Is there anything I can spray or dust the plants with to stop the fungus?

Powdery mildew and leaf death. Powdery mildew is deeper inside the canopy were it is shady.
A. I am not sure what you mean by a white spot, whether this white spot can be rubbed off or whether it is permanent. These plants do get powdery mildew which looks like leaves have been dusted with white flour in some locations.This disease occurs on plants in shady locations.

If it is powdery mildew it usually means they are not getting enough sun or the canopy of the plant is not open enough for air movement. Powdery mildew, unlike other fungal diseases, requires very little humidity to become a problem. It is spread by splashing water from overhead irrigation hitting the leaves and splashing on others carrying the disease to these leaves and so it spreads.
You can buy a dust or spray to control powdery mildew but that just circumvents the problem and it will come back. The long term way to control it is to get more sun on the plants (move or prune them to open the canopy up), improve their health with fertilizers and appropriate watering. If the plant is under watered the canopy will be very open and I doubt you would have powdery mildew unless it is in shade or partial shade.
A white spot can also mean scorching of the leaves due to direct intense sunlight. This type of damage cannot be rubbed off with your fingers. It is permanent damage to the leaf. If this is the case then the plant may be in the wrong spot (intense sunlight or lots of reflected heat and/or light from windows and a west or southwest exposure and planted in rock.
 If this is the case then you need to move it away from this intense location into one that is more cooling with less intense sunlight. This is not a desert plant and cannot handle this kind of exposure. It does not like rock mulch very much so put it in organic mulch on the soil surface.
If it has only one drip emitter, put two or three depending on its size. If you are watering every day then water deeply every other day or every third day now. Make sure you fertilize this plant in the spring with a good tree shrub fertilizer.

If you want to move this plant, you can move it to a new location in October, moving as much of the soil with it as possible, and mulch it. Predig the hole and move it and plant it in less than 30 seconds once the roots are exposed.
Euonymus does much better with a wood surface mulch.Neem oil is a pretty good organic control for powdery mildew.

Why Does My Orange Tree Have No Fruit?

Q. I have a dwarf orange tree planted a little over a year ago. There have been no oranges on the tree. I have fertilized and I think I've been watering it correctly. The tree appears to be healthy just no fruit. Any suggestions?

A. Dwarf orange is not much help to me. The subject of oranges is huge. I need to know what type of orange it is, whether it has produced flowers or not and no fruit, or no flowers and no fruit. Varieties vary from early ripening - about 8 months from bloom - to late - up to 16 months from bloom.
There are three main groups: The normal fruited, without navels and with light orange colored flesh; the navel oranges, with a distinct navel development at the end; and blood oranges, with red flesh and juice.

There are about 73 varieties but US production focuses on Valencia, Washington Navel, Hamlin, Parson Brown, Pineapple and Temple. For home gardening there are many more than these six available from nurseries.

Remember, in southern Nevada growing citrus is marginal. Our winters or just too cold. That is the major limiting factor. The usual reason for not producing fruit are winter freezes.

Citrus should be planted in protected areas out of winter wind. They should be protected in the wintertime from cold. There is an excellent publication from Arizona on protecting citrus from cold weather.

Discouraging Root Growth Around Irrigation Pipes

Q. Having had several somewhat expensive repairs because of root damage to my sprinkler system, I am wonder if you have any suggestions for preventing/lessening such damage. I was told by one sprinkler technician that putting copper (he suggested pennies) in the ground would discourage root growth in the area. Is there any truth to this?

A. I am guessing the root damage was lifting the pipe out of the ground because roots were growing under the pipes. Roots will not grow into pipes unless there is existing damage to them, allowing for their entry but then there would be water everywhere. The other type of intrusive growth would be in drip irrigation emitters.

The best ways to avoid damage are to bury pipe deep, plant woody plants far enough from irrigation pipe so that it does not become a problem (preferably outside the irrigated zone of the plant) and use the appropriate type of irrigation pipe.

The best way to keep roots from lifting pipe and damaging them is to bury the pipe deep, as it should be. Irrigation laterals (pipe coming from irrigation valves directly to a sprinkler or other type of emitter) should be a minimum of twelve inches deep (0.3m).

Irrigation lines that are under constant pressure (pipes before the valves) should be a minimum of 18 inches deep (0.5m). All plastic pipe used for irrigation should be a minimum of Class 200 PVC when installed after or downstream of the valve. All pipe under constant pressure (before the valves) should be Schedule 40 PVC.

Class and Schedule refer to the internal pressures that these pipes can withstand which is related to the thickness of the walls of the pipe. All pipe installed should be "fresh" pipe, undamaged by the sun.
Class 200 PVC pipe on the left and Schedule 40 on the right
The PVC in most irrigation pipe is rapidly damaged by the sun if left exposed to it. You will see this damage by discoloration of the pipe. In extreme cases it will turn the PVC black from discoloration due to damage. Once this damage from the sun occurs, the pipe becomes very brittle and has no capacity for bending. It will shatter easily if bent.
Sun damage to white PVC irrigation pipe

Do not use, or do not let a professional use, PVC pipe which is discolored. Pipe exposed to the sun should be painted or wrapped. Paint will protect PVC from the sun's damaging ultraviolet radiation.
As far as pennies are concerned. This idea comes from the fact that copper is very toxic to plants.

Copper sprays are used to control some fungal diseases (Bordeaux sprays), copper is used to control mildew which are plants, copper is used to control algae and mosses which are plants, copper will kill plant roots when used as an appropriate pesticide (yes, it is considered a pesticide if it kills plant roots!) and copper nails will kill trees if pounded into the trunk a few inches apart.

The copper that kills is called elemental copper and must be available to react with plant roots. Perhaps plant roots in direct contact with pennies will be killed but plant roots just a few inches away probably will not. This would mean that if you were to protect the pipe you would have to line the pipe with pennies.

Just a side note. Whenever we pound anything into a tree we need to make sure the damage is minimal. Of course pounding anything into a tree damages it but some things are more damaging than others. Zinc galvanized nails will damage a tree more so than stainless steel. Whenever anything is put into a tree it is always best to make sure it is stainless steel if it has to be done at all. 

Oleanders In Containers Not Blooming

Q. I have two pink dwarf oleanders planted in 18 inch clay pots which are healthy looking but very few blossoms. One of my “expert” friends says simply that "oleanders don't like pots". Another "expert" says that I'm watering too much. Are either of these guys right or do you have any suggestions that might get some some blossoms?

Oleander flowers
A. We have dwarf oleanders at the Research Center in containers and they bloom just fine. The usual reasons for a lack of flowering are not enough light and pruning them incorrectly. Oleanders use a lot of water when it’s present.

There might be a couple of things you could try. Oleanders should be in full sun. They love the heat, and they love water and fertilizer to perform their best.

If the container is smaller you might have to water more often. 18 inch containers are not that large and don’t contain a lot of soil. If the soil volume is not large, the plant may not have enough water in the soil to last between irrigations.

Oleanders that are not getting enough water will look normal but have a very open canopy and not bloom well. Containers are not very forgiving when it comes to water. The water in that soil can be used up fairly quickly.

You can try using a soil moisture meter that you can buy from the nursery for about $7 and check the soil moisture before you water. Water when the meter is about half way between wet and dry, do not let the soil go totally dry.

Next, use a fertilizer like Miracle Gro or Peters and water it into the soil about once every six to eight weeks. Oleanders growing in the ground do not need to be fertilized as often.

Next, cover the soil in the container with mulch to help keep the soil moist. About three inches would be enough.

If oleanders are young or if they are pruned with a hedge shears they will not produce any flowers or very few. Don't prune it with a hedge shears if you want flowers, contrary to how you see it done around town. 

Will Eggplant Produce Through Fall and Winter?

Q. Will my eggplant plant continue to produce through the fall and winter?

Thai purple eggplant

A. They are warm season vegetables so they slow down considerably as temperatures drop.
Although eggplants will keep growing and flowering, they are more productive if cut back and allowed to regrow during late summer. Cut plants to about 6 to 8 inches in early August, cut at a crotch, fertilize and allow them to regrow.
Fertilize and keep soils moist to force them to regrow. The second crop will be ready to harvest in about six weeks after cutting them back. In Louisiana, eggplants are sometimes trellised and sheared late in the season for increased yield and quality.
The ideal temperatures for eggplant is 70 to 80 degrees F in the day and 65 to 70 F at night. Very few places, outside of a greenhouse, gives those types of temperatures consistently. Obviously, they do well in temperatures higher and lower than this. Fruit abortion can begin around 95 F even though the plant itself can handle heat.
Eggplant flower

As temperatures drop in the fall, eggplant still sets fruit but fruit set is not as reliable and fruit development is slower. Eggplant is generally more sensitive to cooler temperatures than its cousins, tomatoes and peppers.
Flowers consistently set fruit down to 60 F nighttime temperatures. Eggplants begin to get chilling injury at temperatures below 50 F.
Staking may be necessary if plants get big and full of fruit. Fruit touching the ground will spoil. Harvest fruit when they are one third full size and shiny. Over mature fruit will be spongy, the seeds begin to harden and the fruit surface becomes dull rather than shiny.

Snap fruit off of the plant but they will keep longer if they are cut from the spiny stem. Mulching helps fruit to set and improves fruit quality.