I picked up a second-hand copy of Andrew Dalby and Sally Grainger's The Classical Cookbook cheaply and am reading. (A copy of The Flavours of Byzantium is en route).
Much honey and liquamen, as one might expect. Also a good bit of lovage, which pleases me because I grow it and am always looking for new uses for it.
One thing I didn't realise is that ancient Greek and Roman cooking seems to have used rue (Ruta graveolens) as a seasoning.
I know what rue is, what it looks like, and that one can grow it in Maryland. But I had picked up the notion that rue is poisonous as well, so I was a little surprised by the book's assertion that it's perfectly safe to eat.
(I love Research Time).
And the answer is ... it depends on what part of the plant you're talking about, how much you're using, and who you ask. Hurrah for indeterminacy.
Everyone agrees that 'people with sensitive skin' should avoid contact with the leaves on sunny days. The combination of the oils from the leaves and ultraviolet radiation can result in skin lesions and blisters. However, you need both the leaves and the UVA exposure to trigger the phytophototoxic reaction, and it seems you can forestall it by scrubbing well with soap and water and staying out of the sun for 48 hours.
As a culinary plant?
Most sources agree that pregnant women or women trying to conceive should not consume rue because it may induce miscarriage.
Provided you are not in those two categories, British and European sources tend to say it's fine to use it as a seasoning. They point out that people have been using it as a seasoning for thousands of years to no ill effects and, because it's bitter, you're unlikely to overdose yourself on it anyway. The consensus outside North America seems to be that a leaf in your bundle of pickling herbs, or included in your recreated moretum is not going to harm you.
American sources, however, tend to treat the whole plant as being potentially deadly and not to be eaten under any circumstances. Most of the European sources laugh this off as typical ridiculous American overreaction, unless (as at least one ponders) rue produces different metabolites in North America than it does in Europe. This is possible, but I am not sure how likely it is.
So, do I plant rue in my garden next spring, if only on a cloudy day and while wearing gloves and long sleeves? Possibly; it's a host plant for the larvae of the Giant Swallowtail and Eastern Tiger Swallowtail butterflies. Do I cook with it? I'm not sure.
Elizabeth Barrett Browning