Question
Hello again Dr. Vann:

I live in Southern California where, for many years, as other residents do, I've lined the fence line around my house with oleanders.

In recent years the oleanders in our area have succumbed to a disease that the Dept. of Ag. used to prevent by the periodic release of a beneficial insect. But as of a few years ago, under pressure from people worried about the plant's potential for poisoning horses and pets, they stopped the release program, hoping, apparently, that if enough oleanders died, area residents would abandon them and adopt the use of alternate, NON-poisonous plants.

As a result, along my own fence line, while some of the plants are healthy, many are dead. I'd considered just buying new plants to replace the dead ones, and then I got the idea that I might replace the dead ones with new plants grown from cuttings from the healthy ones.

My reasoning is that the healthy plants might carry some inherent resistance to the disease that the dead ones didn't have, and that by using cuttings from the healthy plants, I'd end up with a disease-resistant population of oleanders.

Does my theory have any merit? Do you think that my healthy plants are more disease-resistant than the dead ones, or is it just LUCK and a roll of the dice that they weren't infected?

In my own yard I don't have entire rows of dead plants. I'll have a single dead plant between several healthy ones, or maybe 3 dead plants between 2 healthy ones; there doesn't seem to be any logical pattern. They all get plenty of water, and the other yards with oleanders look the same.

ALSO, in a recent question, I asked what was killing some trees in my yard, and you answered that they'd been succumbing to stress that could have been cause by several factors.

Though in the case of my poplar, I couldn't figure out the cause of the stress, I found that the English walnut was beginning to succumb to stress from a lack of water.

About a year ago I switched my automatic watering system from daytime to late nighttime operation, and because I hear the sprinklers come on every night about the time that I go to bed, I stupidly assumed that everything was working fine.

Prompted by your answer, I CHECKED the sprinklers, and discovered that the one that provided most of the water to the English walnut was clogged. I cleaned its filter screen, it works fine now, and I'm guessing that will solve the problem.

I'm the author of a popular book on amateur rocketry, and as a thank you for your answer to that question, I'd promised to send you a signed copy. But when I tried to get back in touch with you to ask for your mailing address, I got a message saying that you were overloaded with work and temporarily refusing messages.
If you can now email me your mailing address, I'll send you a copy. Many thanks,

David Sleeter/Moreno Valley, CA

Answer
David:
Your theory does indeed has some merit. It is difficult to say how much, because these "healthy" plants could have merely "escaped" disease so far rather than being truly resistant. More through testing would need to be done on these remaining plants to confirm true resistance or just escapes. As you mentioned, it could be just a roll of the dice.

On the watering/sprinker issue, here in our part of the world, we encourage people to set their sprinkers for an early morning cycle (to run between 4-8 am)rather than a late evening cycle so the lawngrass doesn't stay wet for long periods. This late evening practice encourages a lot of turf grass diseases. We tell folks that the grass needs to be mostly dry by mid day-- so if you water in the late evening, keep an eye out for any turf diseases.  Your watering goal for turf should be deep, but infrequent waterings, rather than frequent and shallow waterings. This will encourage deep roots--by watering deeply but infrequently.  Consider buying a cheap rain gauge so you can monitor how much water is going out at a given time period. Trees should be watered deeply,but infrequently as well.

Thanks for your kind offer in reference to your book, however it is not necessary. I just enjoy visiting with you and hopefully give you some insight with your questions and thoughts.

Keep me posted!

Regards
Steve