Q: I have had oleander trees for many years. Lately, they lose their leaves but one tree still look healthy. I water them every day in the summer. Is there any way I can bring them back to health again? I’m not sure these trees need lots of water or less water.
A: It is a misconception that oleanders do not need much water. We get this idea because they are very tolerant and can survive when there is not much water available.
As less and less water becomes available to them, they start to look bad. Usually they begin to drop their leaves and their canopies become very open. The nice thing is that when water becomes available to them they respond nicely, having survived a potential death blow and continue growing again, eventually becoming full.
Oleanders, contrary to some popular opinions, like to be watered deeply and about as often as you would water your shade trees. Watering every day is too often. At this time of year you should water them deeply about every three days. They enjoy a fertilizer application in the early spring and winter pruning, when necessary.
We try to avoid pruning them during their flowering period in summer. So, get your size control done with pruning during the winter months. If your shrub looks scraggly, then go ahead and prune out the tallest stems (usually the oldest and biggest in diameter) to the ground now as they will probably not look very good once the plant begins to show healthy growth.
These longer stems without many leaves will probably begin to bend toward the ground as vigorous growth resumes and the plant may look floppy. As you get this plant on its proper irrigation schedule you will want new strong, healthy and erect growth to come from the base.
Q: I’m having problem with roses and shrubs. The leaves turn brown and seem to have some sort of fungus. I have attached pictures for you to look at. I appreciate it if you could tell me what is the problem and possibly how to take care of it.
A: Thank you for the pictures; they were very helpful. This is what happens to roses frequently in our climate and our soils. The principle problem is a lack of soil improvement. It is also similar to a lack of water, so make sure each plant is receiving 2 to 5 gallons at each watering.
The leaves are scorching and the plant is dying back because the plant is losing its good health. This is most likely not due to insects or biotic diseases. Roses do not like our desert soils unless the soils are amended.
Amended soils are more similar to the soils where the roses originated. Soil improvement is a continual process that starts when the roses are planted and continues throughout their lives .
As the years go by, the amended soil begins to disappear and become more mineralized . Unless we continue to apply organic soil amendments and cover the soil with organic amendments that continually break down, desert soils will revert back to their native states.
I suggest that if these plants are more than 50 percent dead or dying you should replace them. Use plenty of compost mixed with our native soil when you replant them. Try to incorporate this compost into the surface of the soil around existing plants.
You can try applying some organic fertilizers and amendments around the plants, such as guano or composted manure. In late December, apply either some Miracle-Gro or Rapidgrow around the base of the plant. Also apply an iron chelate that contains the acronym EDDHA in the ingredients. Follow the label directions.
Apply an organic surface mulch that will continually decompose back into the soil. Use coffee grounds or used tea bags (without the bag) on the surface of the soil as well. Continue to replenish this surface mulch as it decomposes and work it into the soil. You will see improved plant growth and health and a dramatic change in soil color in the first one to two years.
Q: I live in Anthem and get a lot of strong winds. I’ve attached pictures of the multitrunk palo verde tree in my front yard, which has always done very well and still appears to be fairly healthy. It was a 24-inch box tree that was planted six years ago. Earlier this week, I noticed that the front part of it was leaning toward the street. Upon closer inspection, I saw that the trunk is splitting away from the rest of the tree. I raked away some of the rock mulch and saw several worms, so there must be many more down there. They don’t look like the pictures of palo verde grubs that I saw online, but I’m sure they’re causing damage to the tree, whatever they are.
A: The trunk is splitting at soil level and it looks like debris and soil has accumulated in the split.
I think what you are seeing is a splitting of the trunk at a narrow crotch angle. I can’t tell for sure because the attachment at the crotch is at soil level or below ground. When trees have limbs that are poorly attached to a trunk they begin to weaken at this point as they get bigger and heavier. As it weakens, the poorly attached limb begins to split from the trunk.
The point of attachment of this major limb is so close to the ground it appears that soil and debris have accumulated on the top of the split. This accumulation of dirt and debris may have caused some decay in the limb and trunk.
I don’t recognize the insect or worm in the picture. I don’t believe it is damaging the healthy parts of the tree but is co-existing with the rotting parts of the wood. I think you would be fine if you just remove the limb that has split from the trunk, pull the soil away from the trunk and let it heal in the open air for a several days to a couple of weeks before replacing the soil against the trunk.
It will be a question of whether the loss of a major limb like that is going to be acceptable to you visually since the tree will be out of proportion for quite a long time.
Bob Morris is an associate professor with the University of Nevada Cooperative Extension. Direct gardening questions to the master gardener hot line at 257-5555 or contact Morris by e-mail at [email protected]
If you have fertilised too much, don’t be afraid, oleander deals with this a lot better than other blossoming plants, only the leaves can grow brown from the outside. If that’s the case, you have to wash out the excessive nutrients from the root ball with a lot of water.
If you want to successfully cultivate your oleander over many years, you cannot go without a trimming from time to time. But remember, this Mediterranean bush should only be trimmed cautiously. We recommend spring time. Since the plant’s roots are active during the whole year, trimming them during autumn would evoke another budding.
- wear gloves (the plant juice is poisonous)
- don’t trim blossoms!
- on the blossoms’ tips new blossoms can develop
- remove seed capsules
- trim cuttings to 15 cm during early summer
- long and branchless shoots should regularly be trimmed
- always cut shortly above a leaf pair or bud
- older and bare plants can be trimmed down to its base frame
- always cut all shoots that are thinner than a finger
While trimming Oleander keep this in mind: if you cut into old wood, ne and long shoots will occur. If you cut into blossom regions, you will get shorter shoots that will bloom quickly. You have to find a good ratio.
Pot plants need a cool but bright location during the winter. The brighter the oleander overwinters, the more blossoms can be created. Before putting the plant into its winter location, you should check for pests and, if necessary, treat the plants. Let you plants be outside as long as possible, most plants can tolerate a bit of frost.
- only put them in their winter location if temperatures drop to ca. -5 degrees celsius
- until then, keep it in a protected location near your exterior wall
- put it into a cold house if there’s permanent frost
- Temperature: 5 to 10 degrees celsius
- as bright as possible
- the colder a plant is, the lass it has to be watered
To keep oleander in a warm room during winter is not the greatest thing, since even the brightest place inside the house will not suffice and the plant will create long and thing shoots (etiolated). These shoots will take too much from the plant and they will also not be able to survive outside. If you have a conservatory, or greenhouse, you can keep the oleander warmer starting in March and water it generously. All other pot plants have to get gradually used to outside light and temperature starting at the end of April.
Nerium oleander can be bred with cuttings, or seeds.
The oleander’s cuttings are quite easily take root. To do this, cut of a few fresh shoot tips during the spring or early summer and put them into a pot filled with soil.
- Shoot length: 15 cm
- at least three pairs of leaves
- remove lower pair of leaves
- lightly scrape off the bark
- put it into moist substrate
- Substrate: breeding soil with clay
- always keep lightly moist
- Location: half-shaded and warm
After approximately four weeks new shoots or leaves show themselves and make clear that the cutting has created roots. It can now be put into the same substrate as grown plants. After the cutting has reached a height of ca. 20 cm, the shoot can be shortened to two to three nodes, to encourage branching.
It is possible to breed oleander by seeding, but these plants mostly only bloom after a few years. If you do this, you will have to be really patient until the plant has reached a presentable height.
- Point in Time: Spring
- Substrate: breeding soil, cacti soil
- spread seeds
- don’t cover them with soil (light germinators)
- keep substrate lightly moist
- cover with foil or freezer bag
- Location: half-shaded
- Temperature: over 23 degrees celsius
- Germination time: ca. 2 weeks
- after another two weeks singularise the germ buds
- slowly accustom them to the outdoors
Even if you keep your oleander in great condition, it can become diseased. The most common cause for that are care mistakes.
During hot days a sudden falling of leaves can occur. In most cases, this is normal, since an oleander leaf only ages up to approximately 2 years and the plant doesn’t mandatorily lose its leaves during the winter. Another cause can be water deficiency. Check the root ball, if it’s good dry that’s the cause.
Brown Leaf margins
If the leaves grow brown from the outside and become dry, this can indicate a sunburn, or too much fertiliser. These damages cannot be repaired, but they also won’t really damage your oleander. That’s why you should keep sun protection in mind, especially during the spring. Overly fertilised substrate has to be flushed with a lot of warm water.
If leaves colour themselves in a pale green or if the leaf-veins can easily be seen since they are too dark, an iron deficiency can be the cause. The most common cause is not lacking fertiliser, but a wrong ph-Value inside the ground. In this case fresh soil and fertilising chalk will help.
To keep oleander healthy, you will have to carry out some steps during its lifetime. The biggest problem in this case is a winter quarter that’s too warm. If that’s the case, an infestation with sucking insects like mites or scale insects is inevitable.
Oleander is especially prone to spider mates, if it’s in a location that’s too warm or without good ventilation. The plant should therefore be checked regularly during the year, especially before taking it to its winter quarter and during the colder months. A great remedy is a repeated spraying with a mixture of rapeseed oil, soap and water. By doing that you have to focus on the underside of the leaf as well.
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Deep soak would help oleanders bloom
Question: We bought a house in Sun City about four years ago. In the backyard, we have some old oleander bushes next to 6-foot-high concrete fences. They have seldom bloomed, only a few dark red blossoms. In February, we had them cut down to about 2 feet and had the old wood cut out. In the beginning of May, we fertilized them. They still only have a couple of blooms on each bush.
Should they be hooked up to our irrigation system? Should we have them cut back again? They are about 4 feet high. What can we do to get them to bloom?
Answer: Oleanders, or Nerium oleander, really don’t need to be pruned as much, unless you want them to stay extremely low. This plant is used for hedging and screening, so I don’t recommend pruning so severely, if that’s what you are trying to accomplish. Oleanders do not need fertilizing; they will do well in almost any soil unless they have contracted oleander blight. I think you need to hook them up to your irrigation system or provide them a deep soak at least once a month during the summer. Watering will create more lush growth and possibly more abundant flowering. You can rely on rainfall in the winter.
Q: We have a very tall eucalyptus tree that the tree trimmers said is about 100 feet tall. We have hired several arborists for their opinions about the tree. One said it was a dying weed that should be cut down immediately. Others said it just needs to be thinned out properly to allow the wind through the upper branches. In the past two years, it has been dropping rather large branches. During the warm/hot months of the year, the bark on the tree sheds, and the mess all over our property is prodigious and very hard to clean up. Do you know why the bark is shedding like this? Could it mean the tree is sick? It is not watered. It is a gorgeous, mature tree (30-plus years old) that provides beautiful shade; it would be heartbreaking to have to cut it down. What do you think?
A: With great eucalyptus comes great responsibility. Many species shed and drop their leaves a lot, especially as a response to extreme heat. Any loss of a nearby water source will affect a large old tree. Deep watering or direct injection of water into the root zone will help it get through the summer. Eucalyptus grow fast and provide shade, but the trade-off is the litter.
Q: There is a grass that grows well in the shade. It is St. Augustine. I live in a townhouse, and the yard was bare because of the shade of the trees. I asked the homeowners association to please get me some St. Augustine, and they refused. So I bought two loads myself and planted it. I was 70 at the time. It looks great still — after nine years. This is the grass my mother had in Texas, and she suggested it for my yard. In my other house, I brought home a shoebox full way back when and got my yards up and running. It doesn’t take much water since the roots are close to the surface. Just a thought.
A: St. Augustine is an alternative for the shady lawn, but it comes at a cost. It takes more water and more fertilizer, and it goes dormant in the winter. This grass is popular in the Houston area where rainfall is much greater.
Brian Kissinger is director of horticulture at the Desert Botanical Garden. E-mail your garden questions to [email protected] Read previous columns at home.azcentral.com.
Maintenance of oleander plants?
Your plant looks as if it could do with a good prune, it’s got a bit ‘staring’, that is, too much stem and not enough leaf. I grow these in London, UK, outdoors in sheltered spots, and the one I saw last week is now so bushy, thick with leaves and large, despite a good prune last year, it could do with pruning now – but it’s about to flower. It’s in this condition despite technically being too tender for outdoors in the UK, and having come through what passed for winter this year, so it’ll be twice the size it is now in 3 months. I don’t feed it at all, nor give it compost – but it’s planted with its roots in shade, behind a low wall, and its upper parts in sun, which means it’s probably always got access to moisture deep in the soil under the wall and paving. I’m guessing yours probably could do with a lot more water from late spring throughout summer to get good, bushy, green growth and more bouts of flowering. When pruning, don’t get the sap on exposed skin – some people have a strong dermatological reaction to it. If you decide to prune, you can either do it now and sacrifice the early flowers, or wait till the usual, early crop of flowers is over.
In response to your comment, I almost mentioned the fact that your plant appears to be a ‘standard’ but I find many people don’t understand the term even in the UK, and it confuses the issue! So what you’re describing as ‘a long step’ means you have a straight stem with all the growth coming from the top, often grafted at that point, on the top of the stem, but sometimes a plant is simply trained to grow that way, and that is called a standard. A half standard is similar, but has a shorter stem. I can’t see from the pic whether there’s a graft at the top of the stem, but either way, you can’t cut back past the top of that stem, so shorten all the growth down to 5 or 6 inches if you want, always cutting just above a leaf node, but no lower than that. This might encourage more unwanted growth elsewhere because yes, when you have a ‘standard’, you do remove any growth coming from the ground or off the long straight stem, to keep the form and shape. Even so, if you rub out or remove the unwanted growth as soon as it appears, the topgrowth should still grow thicker and bushier.
To Oleander or Not to Oleander
This is the first article in a series of reports on local poisonous plants.
Area gardeners/landscapers have an important decision to make:
1. To permit the oleander in their yards.
2. To keep the oleander out of their yards.
Why should one have to decide this issue? The oleander is both very beautiful, and at the same time, extremely deadly.
Flowering oleanders with their striking color range of white to red and shades of yellow, pink, and salmon make exceedingly attractive borders and hedges as they easily reach 8 to 20 feet in height. It is no wonder that many Cochise County landscapes feature them.
Besides their good looks, oleanders tolerate all types of soil, as well as heat and cold temperature extremes, plus they grow easily and rapidly.
A super plant for your yard? Remember that ALL parts of the oleander are poisonous if eaten. Exercise extreme caution with both children and animals regarding its leaves and flowers. Horses experience a bloody diarrhea after consuming minute amounts of this plant and it proves to be fatal to them almost 100% of the time. Also, oleander fumes are dangerous, so don’t use the wood for barbecue purposes.
The decision to permit the oleander in your yard is your decision.
If Oleanders are diseased, consider these alternatives
Question: I live in central Phoenix in a neighborhood that dates back to the early 1900s. Many of the plantings are substantial; my neighborhood is surrounded by large oleander hedges that were planted at least 50 years ago. Today, most of the oleanders are dead or dying. What is causing this? What can I safely plant to replace the screening my oleanders provided?
Answer: The death of your oleanders is most likely from oleander leaf scorch. This disease was first noticed on oleanders in Southern California in the early 1990s and has spread across warm regions of the southern United States.
Oleander leaf scorch is caused by the bacterium Xylella fastidiosa, which is spread by the glassy-winged sharpshooter. Once the bacteria has entered the plant, it moves through the xylem and eventually kills the plant. No current insecticides are effective in controlling the disease, but early removal of infected plants will reduce the spread. I would plan on replacing all oleanders in areas that are showing the die-back. It usually takes three to five years for the plants to die once you start seeing the symptoms. In hot desert regions, symptoms can progress more rapidly.
Now that I’ve shared the bad news about oleander leaf scorch, let’s explore some viable options to replace your dying oleanders. First, remove all of the plants and their stumps. If your plants are old and established, I would have a professional attack this one. You will probably need to do some serious backfilling of soil once your oleanders are removed. I would use a well-draining soil mix containing 50 percent clean fill dirt and 50 percent sandy loam. Before replanting, make sure the newly exposed bed drains well.
Now you can explore planting options. Remember what you are trying to accomplish when selecting options for your missing screen or buffer. The oleanders probably hid a myriad sins and also provided privacy. These are my recommended plants for oleander replacement:
• Vauquelinia californica pauciflora, or Arizona rosewood. This is an extremely tolerant, rugged plant that is a good evergreen replacement for the oleander in the lower deserts. Arizona rosewood is used for informal screening and can grow to 25 feet tall and 15 feet wide. The leaves are leathery and shiny. Small white flowers appear in late spring.
• Quercus virginiana “Cathedral,” or the Cathedral live oak. This columnar hybrid live oak has proven itself as a great replacement for areas where large oleanders have been lost. The Cathedral live oak has the dense foliage and glossy leaves of the live oak but in a less spreading form. This live oak can be left growing full to the ground, and I would recommend planting it on 15-foot centers for maximum screening. Eventually, these will grow together and create a full, drought-tolerant screen. This would be a good choice for areas that need more “instant” replacement screening.
• Dodonaea viscosa, or hopbush. Another drought-tolerant alternative replacement, it can create an informal hedge to 12 feet. Hopbushes are evergreen and commonly found in the green and bronze form. Purpurea from Australia is a purple form and is less hardy than the native green forms from Mexico.
• Laurus nobilis, or Grecian laurel. It is a large, multitrunked evergreen shrub that grows up to 25 feet by 15 feet. The leaves are dense, leathery and aromatic. If you leave all the growth to the ground, I think this makes a nice alternative replacement for the oleander in small garden areas. Deep watering in the summer and planting in well-drained soil are essential.
• Ligustrum lucidum, or glossy privet. A large, multistemmed tree from China, it does remarkably well in our lower deserts as a screening plant. The leaves are glossy and 4 to 6 inches in length. This plant is messy but will grow rapidly. I suggest not planting this near a patio but as a backdrop screen for a buffer.
• Citrus, or sour orange. These are being used as screens in place of Oleanders. These are decorative and can grow to 25 feet. If you need screening fast, this may not be your answer. The sour orange grows slowly and needs citrus fertilizer annually to keep its deep green color in our soils. I have seen this plant looking good if it is cared for properly and not over-pruned.
• Elaeagnus pungens, or silverberry. It is a little-known, drought-tolerant screening alternative for the lower and intermediate deserts. The silverberry is a fast grower and can reach 12 feet in as little as five years. The foliage is evergreen, with a shiny, glossy green character above and a silver look on the underside. The flowers are extremely fragrant and appear in late winter. I like this plant for its spicy aromatic quality.
Brian Kissinger is director of horticulture at the Desert Botanical Garden. E-mail your garden questions to [email protected] Read previous columns at home.azcentral.com.
Oleanders: Plant Care and Collection of Varieties
An attractive evergreen shrub for warm climates, oleander produces heavily scented, colorful flowers all summer and fall.
Oleanders bloom from summer to fall, with fragrant flowers in shades of apricot, copper, pink, lilac, red, purple, salmon, yellow, and white, depending on variety. The plants are best adapted to the west coast, southern states, Florida, and Texas and will withstand dry conditions and wind, as well as salty, marshy soils, making them popular in coastal regions. Oleanders grow 6 to 12 feet tall and wide, and some varieties can be trained to grow into small trees up to 20 feet tall. The flowers are very fragrant.
All parts of plant are poisonous to humans and animals if ingested; the plant’s sap can cause skin irritation in some individuals.
Special features of oleanders
Choosing a site to grow oleanders
Ideally, select a site with full sun to light shade and well-drained soil. However, oleanders are adaptable and will withstand dry conditions as well as marshy soils.
Apply a layer of compost under the plant each spring, spreading it out to the dripline (the area under the outermost branches). Add a 2-inch layer of mulch to retain moisture and control weeds. Water plants during the summer if rainfall is less than 1 inch per week. Prune oleander after the main bloom period to encourage bushier growth and more flowers, and to reduce the size of the shrub.
Plant in spring or fall. Space plants 6 to 12 feet apart, depending on variety. Dig a hole only as deep as the root ball and 2 to 3 times as wide. If your soil is in very poor condition, amend the soil you’ve removed from the hole with a small amount of compost. Otherwise don’t amend it at all. Carefully remove the plant from the container and set it in the hole. Fill the hole half full with soil, then water it well to settle the soil and eliminate air pockets. Let the water drain, then fill the remainder of hole with soil and water thoroughly.