FARGO — If you see it on the internet, it must be true, right?

That makes for a good chuckle, but it can be problematic if you need accurate facts, such as whether the plant your cat just chewed is poisonous or not.

When researching material to support our gardening columns, I rely heavily on internet material from universities whose research backs the recommendations they make. That’s reassuring for important topics like whether or not indoor plants are toxic if a pet or child consumes part of a houseplant.

The University of Connecticut defines a poisonous plant like this: “One that contains a chemical substance which produces a harmful reaction in humans or animals when taken in small or moderate amounts. This could include allergic reactions, skin irritation, or internal poisoning. Individuals can react in different ways after contact with poisonous plants, depending on their sensitivity level.”

It’s important to emphasize that poisonous does not necessarily mean deadly. A plant that causes skin rash fits the broad definition of a poisonous plant.

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The national Animal Poison Control Center classifies houseplants into three groups based on toxicity. Mildly toxic plants that cause slight gastrointestinal distress with possible vomiting and diarrhea include fiddleleaf fig, spider plant, pothos, dieffenbachia, peace lily, philodendron, calla lily and Chinese evergreen. Exposure to these is not considered life-threatening, but if pets show more severe distress, see your veterinarian.

Moderately toxic houseplants, according to the APCC, include dracaena and jade plant, causing slightly more severe gastrointestinal irritation. Vomiting and diarrhea are common.

Considered severely toxic are cycad sago palm and Easter lily, which can cause liver failure, kidney injury, gastrointestinal irritation and seizures. Consumption of plant parts in sufficient quantities can be fatal, and cats are especially vulnerable.

The Universities of Utah and Connecticut expand the list of plants containing toxic compounds to also include amaryllis, anthurium, English Ivy, schefflera, kalanchoe and monstera. Although reactions can vary with individuals, the most common effect is irritation of the mouth or stomach.

The University of Connecticut lists plants that are considered safest around pets and humans: African violet, aluminum plant pilea, bamboo, Boston fern, cast iron plant, wandering Jew, zebra plant, Christmas and Thanksgiving cactuses, coleus, geraniums, aralia, hoya wax plant, orchids, Norfolk Island pine, pepperomia, prayer plant, Swedish ivy and maidenhair fern.

When researching this article, I noticed discrepancies even between reliable sources. Part of the confusion seems to stem from our interpretation of the term “poisonous.” The belief that the poinsettia is deadly poisonous was debunked decades ago. However, the milky sap can cause skin irritation in some individuals, so it appears on some poisonous plant lists, even though it’s only a mild skin irritant. Because of this reaction in certain individuals, it can fit a broad interpretation of a poisonous plant.

The Canadian Poisonous Plants Information System says, “Much literature on poisonous plants is anecdotal and therefore of limited reliability. Many plants are only mildly poisonous or cause symptoms in unusual circumstances such as when prodigious quantities of material have been consumed.”

Most reliable sources are quick to point out that their lists are not meant to be comprehensive, but include the current best recommendations.

The University of Connecticut offers the following wise advice:

  • Be aware of the identity of your houseplants and learn if they pose potential threats to children and pets.
  • It is also important to realize that many plants need to be consumed in considerable quantities for poisoning to occur. Often, toxic plants taste bitter or acrid, and children and pets may not ingest large amounts.
  • Young children, especially, should be taught not to put unknown plants or plant parts in their mouths.
  • Any plant may cause a reaction in certain people or pets.
  • If a plant is eaten, remove the rest from the mouth and rinse the mouth with water.
  • If a houseplant is ingested by children or pets and poisoning is suspected, call your family doctor, nearest emergency room or veterinarian immediately.
  • The number for the National Poison Center is 800-222-1222. They can tell you if a plant is poisonous and what symptoms might be expected with a particular toxin. You will need to provide them with the identity of the plant.

Don Kinzler, a lifelong gardener, is the horticulturist with North Dakota State University Extension for Cass County. Readers can reach him at kinzlerd@casscountynd.gov or call 701-241-5707.