Toxic in what way? For pets? Kids? Adults? Do you want to kill someone in some obscure way? Or are you worried about grazing sheep getting in? Or maybe are you worried about what to avoid?
For instance, there's a wild parsnip plant around here (Maine) that you could probably eat all you want an touch without any troubles. But if you get a little of the sap on you and then expose that area to the sun, you get terrible blisters! In theory cultivated parsnip plants have a similar trait at certain periods. I've recently met some people who claim an allergy to any nightshade family, but I've never experienced any issues. Rhubarb leaf is considered toxic, but how much do you need to consume?
That url was helpful, but I think it also highlights how little is published about toxic plant parts, especially the common ones. Pokeweed was only a 2. Water hemlock and apple seeds were both rated a one, but I think a distinction should be made between apple seeds and the most deadly plant native to north america. Physalis spp. contains the ground cherries (which are commonly sold in heirloom seed catalogs); there are some edible ground cherries and some toxic ones. And so forth... Maybe needs more specificity about exactly which members of the genus are toxic and what parts, etc.
I realize toxicity is highly depended on many factors (weight of person, part of plant eaten, amount eaten, allergies, etc.).
Kinda makes me wander...I've never seen a nursery or plant catalog warn against the tomato plant being toxic if parts other than fruit is ingested. However, coffee must be labeled as hot or you can be sued haha.
What landscape company warns those azalea bushes are extreemly toxic and a wisteria seed could kill a kid?
Also, if you did die or get sick from eating certain part of a common edible, I wander if they would put two and two together that that is what hurt you?
Just read the toxins in azalea that can hurt you are also found in honey from azalea flowers but I've never been warned.
Rhubarb leaves are toxic, but not the stems. Rhubarb makes an incredible pie when mixed with blackberries.
Probably the most important thing about growing food is washing it, and keeping manure from splashing up on it so there are no e. coli issues. Even store-bought vegetables need to be washed thoroughly because of handling issues and noro virus.
Toxic/poisonous landscape plants, there are plenty of those, but I have lived with many of them, like oleanders and foxglove flowers (digitalis), and never had a problem.
Don't fall for the My-Place-Is-Special, It-Won't-Happen-Here Syndrome.
In my own food gardens I have....(I'm only listing the edible parts of the plants. Not things like the leaves of the tomato plant, etc.)
...red kidney beans. One can get sick if they are not properly cooked.
...lab lab beans. Must be cooked properly before eating.
...chaya. The leaves need to be cooked before eating.
...potatoes. Any green spots need to be removed before eating. Any tubers overall greenish should not be eaten.
...taro. Must be cooked long enough to break down oxalates crystals.
...wheat. Do not eat grain showing signs of mold (ergot poisoning).
...raw leafy greens (spinach, chard, beet greens, kale, parsley). Persons with medical conditions where they need to restrict oxalate intake may have problems with certain raw leafy greens.
I think that's it for my edible garden plants.
It's never too late to start! I retired to homestead on the slopes of Mauna Loa, an active volcano. I relate snippets of my endeavor on my blog : www.kaufarmer.blogspot.com