You are assuming a level of toxicity for oleanders that only exists in bad TV shows. I have two tomato plants growing right next to the oleander hedge, and no one has dropped dead yet from eating the tomatoes.

Oleander toxins are "glycosides", they are readily decomposed by almost any fungus, mold, or bacteria. Shredded oleander branches degrade quite nicely in a compost heap just like all the other plant matter. Just don't eat the compost while it's fresh.

Cut it down, shred the branches for compost, dig out the roots down a foot or so with whatever works. After 30 years, backhoes and high explosives may be necessary. At the very least, a mattock or pick-axe will be needed.

The roots will decay where they are, and the fruits and veggies and chickens will do just fine.

Oleander is poisonous to humans if ingested because of the cardiac glycoside in it. Never read anything about allelopathy from Oleander, and it is not a known juglone producer in any literature I've ever read.

http://www.employees.csbsju.edu/SSAUPE/biol106/lectures/poison.htm

and it is not a known juglone producer in any literature I've ever read.

Oleander CAN'T produce juglone, since that's a hormone only exuded by the Juglandaceae, the walnut family and its related species. Allelopathy is an ongoing field of study and many plants produce allelopathic chemicals but few in concentrations serious enough to warrant attention, like the walnut.

Removing the oleander and as much of the stump as possible - same as you would do for any large shrub - is sufficient to assure safety of the soil for edible crops and your livestock.

FWIW, I have never read any evidence that so-called "toxic" substances -like the oleandrin glycosides - can be translocated or drawn up from the soil into other, non-specific plant tissue. Even heavy metals are typically not absorbed by plants in any significant or possibly harmful concentrations.

Thank you for the clarification and expansion, gardengal.

Charcoal has been used to remove toxic from the soil.
As I understand it char works like bio-char, only it takes up toxic. Never heard of using it on Oleandrin.
Tomato plants are toxic, more so in new/young growth.
Many of the plant around you will Kill you, when ingested.
I think that you do not need to worry about the soil.
I agree with other posters.
I worked with a Landscaper when I was in school. At 10 year old I drug large oleandrin limbs & trunks to the curb & have never felt better the next day. I was taught from a very young age NOT to PUT any thing in my MOUTH, unless I knew what it was.

Ah, so those who told me to worry about it without giving me more specific instructions have been watching some bad TV, eh? ;-)

So glad to see a consensus on this - I got warnings from a few different people that I had to be very careful, etc. And then on the chicken forum I googled, there were very mixed opinions about whether the chickens would even bother to eat a toxic plant or if they somehow know better. (My dog isn't too bright, and he seems to know to leave it alone, but I have no idea how much dumber than a chicken he is, or isn't...)

Thanks for the feedback! Now to decide on citrus v pomegranate.....

Animals are amazing that way. Humans have pretty much lost touch with that genetic knowledge of plants.