LAUREL CANYON—Oleanders -“Napoleon is said to have lost a hundred troops to a dinner of meat roasted on oleander wood. In some versions of the story, it was a group of American boy scouts in the 1960s.” The Bible referred to them as “desert roses” – that’s how long they’ve been around. One thing is certain, oleanders have a reputation. Despite this, the plants are all over Los Angeles including the hillsides. Their beautiful bloom and their historically easy maintenance have made them a favorite.
Now we’re battling Oleander Scorch Leaf disease (OSL to the pros). Will the oleander plant become a thing of the past?
If you’re not ready to throw in the towel on your oleanders, I have some practical advice for how to fight the battle against the scorched leaf plague. This however means the end of the “plant it and ignore it” management of your oleanders.
The first line of defense is to keep your plants hail and hearty. We have the habit of taking out our bushwhackers and giving the bush a buzz cut. The buzzing, trimming and shaping are part of the problem. But what happens to the trimmings is also a problem. We tend to let the trimming fall inside the plant stalks. Over time this accumulation blocks the circulation of the air at the base of the plant. This is compounded by the quick sprinkling every few days when we water in 3-5 minute cycles. This serves to bring up the salt in the soil which attacks the roots of the plant. Better to give the bush a slow soak. The buzz cut exposes the stalk of the plant which is where the nasty disease gets its start. I’m experimenting with spraying the exposed stalks with Lysol (without bleach).
Our oleanders have a new nemesis out there – the glassy-winged sharpshooter. I used to see these insects around all the time. They feed on a plant which is infected with the X. fastidiosa bacteria. The X factor in the bacteria is the hybrid which makes it so deadly to oleanders. The bacterium does not kill the original host. However, once the sharpshooter feeds on an infected plant the bacteria in its mouth forever, and is transferred to the oleander, depositing the bacteria into the part of the plant that carries water from the roots to the leaves. The bacteria blocks the plant’s xylem so that no water is transported inside the plant, which makes it looks like it’s been under-watered, and the leaves dry out.
I made up a cocktail of Dr. Bonner’s peppermint soap, baking soda and vegetable oil and spray it on my oleanders, especially after a trimming. My theory is that soap tastes nasty and the evil sharpshooter will go elsewhere to feed. Not exactly rocket science, but gardening isn’t always complicated. The sharpshooters come around twice a year, so I’ll have a chance to confirm my theory soon.
My strategy may turn out to be like deferring taxes, eventually you have to pay up…maybe by then DuPont will have come up with an acceptable insecticide.