HI Caroline glad you are enjoying the articles.
There are several plants that are toxic to honey bees such as laurel, Rhododendron and apple but unless those are the only source of nectar and pollen available bees will generally avoid these plants.
Here's a link to a blog that has a list (scroll down to find them) of good and bad plants. Keep in mind that not all of the plants in the bad list are bad for the bees just certain cultivators in some categories and in others all of them.
Also in some cases there would have to be a lot of the plants present to cause harm to the bees or humans. Some beekeeping articles on the subject say a little bit of the toxic nectar mixed with good nectar does not cause much of a problem.
