I took Xander to the park across the street last week.
He got about half way up the log ramp which leads up to the slide while I walked along on the ground beside him. He stopped and gave the logs, which had seen better days, a good inspection.
"Granny these logs are poisonous!" he declared.
"No, Xander. They are rotten, not poisonous."
Pretty observant and vocabularily advanced for a 28 month old I think.