Another good thread LilRose! Many plants have already been covered, so I'll just back up what Windy Ridge and Onebyone said about finding out about poisonous plants. Along with a description, advice on using it, and a good book in hand, it's important to know that different plants have different uses at different times. The same plant can have an edible part and a toxic part. It's important to know which is which.
Someone mentioned Pokeweed. While it can be used early in the spring, it's best to boil, pour off water and boil again. Later in the year, that tasty plant can kill you. Even getting poke juice in an open cut can cause problems. It takes few berries to kill a child or animal. Same plant, different season.
Same thing with the strawberry. Everyone knows strawberries are delicious and nutritious and the dried leaves make a good tea. Some don't know that though the leaves can be eaten green, and are good dried, BUT halfway through the process of drying, a chemical is manufactured in the leaves that could kill you.
Those delicious mullberries are another one. Good to preserve the juice, makes a good cough syrup, excellent pies, jams, and all kinds of goodies, but it only takes a handful of green mullberries to go on a trip you'd rather not be on. It's hallucenogenic, much like LSD, and can cause serious harm or death to a child.
That rhubarb pie is another one with good stalks and poison leaves.
I mention these just to stress that it's important to learn all you can about the plant.
It's easy to say that the entire cattail plant is useful. From the pollen to the roots.
It's also easy to describe. But, if in the description, I forget to tell you that the cattail rhizome has an outer "peel", you could just as easy be digging the toxic wild iris. Lives in the same location, and has the same description.
Unless you've watched them through a whole season, and seen them flower, many plants can be mistaken for another. Because plants are divided into classes, sub-classes, orders, families, genus and species, you might find a perfectly safe genus with a poisonous species.
Havent' seen anyone mention yet about only taking what you need, and leaving more than you take, and replanting seeds of what you take. It may end up being important to future survival of the plant and human plucker.
Generally speaking, a toxic plant can be tried, but NOT swallowed. If you wonder about a plant, it would be good to break the leaf, rub a little on your skin, and see if, after a few min. you have redness, itching, swelling, or irritation. If not, you might touch the leaf to your tongue and wait a couple seconds for any burning, numbness, tingling, etc. If not, you might try chewing the leaf but NOT swallowing it. After chewing, spit it out. Wait a few minutes and see if there's any reaction. If not, you might want to try the plant. In a very small amount. Wait a day and decided if it's something you want to try again. Remember though, these are very general rules and not hard and fast, I swear it won't hurt you rules.
Guess this post wasn't very helpful in learning what to use, but hopefully it will help in knowing what not to use. There are a lot of good books with illustrated pictures, and everyone can learn to gather safely and responsibly. Happy learning and hunting.
