Last week I told you that certain vegetable plants have edible leaves and stems — like carrot tops and beet greens. I forgot to mention something much more important: Only eat plants that you ABSOLUTELY know are non-toxic.

Rhubarb is an important example: stems are the only part of the plant suitable for human consumption. Leaves and roots contain high concentrations of oxalic acid known to cause stomach irritation and kidney problems. Death from consumption of oxalic acid is rare, but possible.

Pokeweed is another plant that deserves some discussion. The smooth leaves and glossy purple berries of this tall, herbaceous “weed” contain toxins known to cause vomiting, diarrhea, and convulsions in mammals. In extreme cases, paralysis of respiratory organs can occur.

The debate about pokeweed comes because young leaves are sometimes consumed. In 1970, Elvis sang a cover of “Polk Salad Annie” which was written and also performed by Tony Joe White, about a Southern girl who lives on poke greens. (Polk is the spelling on the album.)

Researchers agree that tender young shoots of pokeweed contain less of the toxin than mature leaves, but there is not a hard and fast rule about the height or age of the plant. I also have heard many stories about pouring the water off the boiling greens multiple times before eating, but cannot find research to support the claims.

The bottomline with pokeweed is the same as many other plants: If you aren’t sure, don’t eat it. If you are sure, always make the first try in small quantities.

Other things to keep in mind about poisonous plants:

• Castor beans, sometimes planted for their ornamental beauty, contain ricin in their beans. Castor plants are often considered the most toxic plant known to man.

• Birds’ digestive systems are different from mammals, so consumption of fruit or berries by birds should never be a consideration when trying to determine the toxicity of a plant.

• Only pick from plants that you know are grown for food production.

• Poinsettias are not toxic to you or your pets. The plants contain a milky sap which is known to be a skin irritant and which may upset the stomach if ingested. At the worst, your curious kitty may vomit from eating the leaves.

• Always get plant toxicity information from a trusted source. There is a lot of information out there, but unless your friend of a friend of a friend is an expert, double check what you hear.