Datura, aka Thornapple and Jimsonweed, is a member of the Deadly Nightshade family.  It grows in a lot of warmer climates, including southern Arizona.  They are attractive plants with trumpet-like white flowers and large, dark green leaves.  The plant is a potent hallucinogenic and can be fatal if ingested.   People sometimes ingest or smoke it to get high, often with nasty results.   Livestock and other animals seem to realize this instinctively and avoid eating it - except Lysander.
One evening after work, we noticed that Lysander was having difficulty walking and seemed "out of it."  While Chris took him to the vet, I searched the geese's enclosure for clues as to what might be the matter with him, and soon noticed a datura plant that was just within goose range.  There were a couple of telltale nibbles out of one of the leaves, so that solved the mystery of Lysander's odd symptoms.
We provided supportive care, including tube feeding, while he wandered around in a fog for several days.  After about a week, he was back to normal.  What possessed him to eat the datura in the first place, we'll never know.  We now make sure none of the plants are within nibbling distance of the geese.

We're hoping this was our first and final experience with a hallucinating goose!