Hi. Can anyone tell me if oleander leaves and stems are toxic or allelopathic if used as green manure? I have large lines of it at home and I wonder if I could scatter it over my crop field or orchard. Thanks!
I think you will be fine. I checked the Nerium wikipedia page and GardenWeb. In short, oleander (aka nerium) is only toxic when ingested. You will not be hurt by just touching. Oleander is in the Nerium genus, which is not in the Juglandaceae family, so it does not produce juglone. Most importantly, a user on GardenWeb has personal experience working with oleander and notes that the plants growing where the oleander was are okay.
I was pleased to find out oleander mulch on a pine tree made it healthier than the ones around it.
I tried to take out a large mature oleander and had to cut it down to the ground, so I had several truckloads of cuttings. I piled them at the base of a pine tree that I never thought I would go near, it didn't matter what happened to the cuttings or the tree. But, of course, when you try to find an out-of-the-way place it ends up being exactly where you eventually need to do something.
The pile of oleander cuttings was 10 feet high to start with, not a dense pile, but it was a lot. Nothing else in it, I wasn't trying to compost it. The pile shrunk and shrunk until I almost couldn't tell it was there. Then years of drought happened and all the pine trees around it were showing stress, except that one. That one had more growth and fewer dead needles. There was no extra water from me anywhere near this spot.
I wouldn't think it's a good idea to put it on vegetables, but I will use cuttings on landscape in the future.
For many years I planted a tomato plant next to an oleander. I cut back the oleander to the ground in spring and use the cuttings to mulch the tomato plant. Worked well, I'm still living.
Oleander stems decay quit readily, gone by fall, even in my dry climate.