I've not yet read all of the threads, but perhaps one subject needs consideration when deciding to eat or not eat a plant. What products have been used on the plants by the grower...to feed and to handle insects.
We have commercial greenhouses which supply garden centers, landscapers and organizations.
All of our sweet potato vines are sold as ornamentals but in reality all the tubers/sweet potatoes are edible...and I find them VERY tasty. However, what a grower uses as fertilizer and pesticides could have bearing on whether the plant should be eaten. We use a soy-based fertilizer so the residuals are safe.
That's a good point Eleanor and presents an interesting question.
I would also think growers of ornamental plants would be prone to using more (and perhaps stronger) pesticides, as it is important for their plants to present well. However, I am not familiar with the actual legal restrictions that ornamental vs culinary growers face. Are distributors who grow plants for ornamental purposes allowed to use stronger pesticides, since the assumption is that their plants will not be eaten? Might be something worth investigating for a future article!