We removed an Oleander bush about a year ago, roots and all. Now we would like to plant an avocado tree in the same spot but would the avocado fruit be safe to eat?
Can I Plant an Avocado Tree Where I’ve Removed an Oleander Bush?
This is a question about which there is still scientific debate. This article might shed some light for you: http://www.wildflower.org/expert/show.php?id=9536
If you have doubts, the only sure way is to have the soil tested. Dig up samples from several spots around where the oleander was, you can then mix them together for testing. Your local Extension Service should be able to test for you, or tell you where to send the sample. Explain to them that you're concerned about the presence of Oleandrin in the soil. This link will help you locate an office: https://www.gardeningknowhow.com/extension-search/