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Index : Landscape Plants
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- 26. Common Oleanders Are Uncommonly Tough - Top
I recently heard an account of a man who was "shocking" his pool with high concentrations of chlorine and acid. He let the fill hose run too long, and the "plant toxic" brew overflowed and oozed out into his surrounding landscape. Of course all the plants were burned to a chemical crisp including; lantana, verbena, Texas ranger, and oleander. He thought he would at least try pruning back the plants to see what might happen. The large oleander were trimmed to the ground. In a short time the oleander started sprouting out new leaves. All the other plants were dead. But the oleanders came back looking stronger, fuller and greener than ever!
Although it is possible to kill oleander, it takes a special technique (which I will divulge), but why would you want to? Oleanders are among the most beautiful of all of our flowering shrubs and trees. No other plant blooms with such profusion or over such a longer period of time - April to November. The large bloom clusters, over 8 inches in diameter, blanket the dark green foliage in a range of colors; red, shades of pink, coral, yellow, and white. Flowers may be single or double - some are even scented.
Although most varieties of oleander grow to a height and spread of 20 feet or more, there are two excellent dwarf varieties, that is if you consider 5 feet to be dwarf. They are Nerium oleander ‘Petite Pink' and ‘Petite Salmon'. These are commonly available at most Garden Stores. Of more limited availability are Petite red, light yellow and deep pink selections. Petites can be maintained with regular pruning to a height of 3 feet, so they can be used in a variety of landscape situations. The larger growing oleanders seem to work best when used as trimmed or untrimmed hedges for screening along property lines or trimmed to form a single-trunk tree.
Oleanders can be pruned nearly anytime during the year. Spring pruning may reduce some flowering as buds develop on the branch tips, but it will not hurt the plant. In fact, oleander respond well to severe pruning. Even large plants (except tree oleander) can be cut to near the ground and they will regrow. This severe, rejuvenation pruning may be necessary if plants have grown to large and leggy.
Oleanders require little in the way of care. One fertilization with a nitrogen containing fertilizer in March is sufficient for the year. For established plants, deep-water one or two times each month during the heat of spring and summer. This will give the plant it's best appearance.
All parts of an oleander plant are extremely poisonous - to people and pets. Be careful letting your little dog out in the yard where oleander are planted, especially if he's not too smart or just likes to chew. Ingestion of green or dried leaves or chewing on stems could cause serious consequences. In one report with horses, it was indicated that approximately 1/4 pound of leaves (about 30 or 40 leaves) could deliver a lethal dose to an adult horse. With that being said, reports from the University of California indicate that during a 20 year period, no human fatalities in California were attributed to oleander poisonings, although animals are frequently poisoned each year. Fortunately, the plant is not very palatable, but could be eaten if animals are hungry enough.
In addition to ingestion of plant parts, the smoke from burning oleander is also toxic. But contrary to popular belief, oleander is not toxic to other plants. The reason many plants will not grow underneath or near oleander is not because of a toxin, but rather because of the inability to compete with the thick mat of oleander roots for water and nutrients.
Concern has also been expressed that composted oleander leaves and stems could be poisonous if used in vegetable gardens or around other edible plants. Studies in California indicate that nearly all of the toxin is broken down in the composting process, and regardless the toxin in oleander is not absorbed by plants.
If you must rid yourself of over-grown or out-of-place oleanders, there is an easy way to do it that doesn't involve digging. You'll need to purchase Roundup concentrate weed killer. The concentration of ‘glyphosate', the active ingredient in Roundup should be at least 18%. You can find out by looking on the product label.
Have a good quality pruning saw ready to cut off the stems of the oleander to within a few inches of the ground. In a plastic or Styrofoam cup, pour a small amount of the concentrate Round-Up. Also, have a paint brush, small enough to dip in the cup, handy.
Cut the stems, and within a few minutes of making the cuts, paint the cuts with the concentrate Roundup. The moist stem will absorb the Roundup and move it through the cambium tissue down and distribute it through the roots. This method is guaranteed to prevent the oleander from sending up any more shoots. You can simply let the roots rot in the ground.
The Wednesday Gardening Demonstrations are now in recess but will begin again on September 3rd. Until then, for answers to gardening questions , phone the Extension Plant Clinic at 626-5161. Clinic hours are from 8:30 a.m. to 4:30 p.m., Monday thru Friday. Green Valley residents may call our Sahuarita Plant Clinic at 648-0808, Mondays, Wednesdays, and Fridays for assistance.
Written by John Begeman, College of Agriculture and Life Sciences, the University of Arizona, 520-626-5161. - Updated: June 1, 2003
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