How dangerous
are holiday plants to pets?

Flowers of the amaryllis are less toxic than the bulb. FLORA DE FILIPINAS

Holiday decorations aren’t complete without ornamental plants. But certain seemingly innocuous holiday plants can be poisonous to pets. If ingested, these plants can induce vomiting, diarrhea, abdominal pain and excessive salivation. Seizures, coma or death may occur in severe cases. In 2009, the Animal Poison Control Center at the American Society for Prevention of Cruelty to Animals received 8,000 calls related to poisonous plants during holiday season.

Holly, amaryllais and Christmas rose are some of the most toxic holiday plants, according to Tina Wismer, the medical director of the ASPCA Animal Poison Control Center. The toxic effects of these plants come from specific bioactive compounds.

“Holly contains triterpenoid saponins; these are soaplike substances that irritate the digestive tract and can cause severe vomiting and diarrhea, sometimes with blood. Fortunately, most species of holly have prickly and leathery leaves that are not normally attractive to pets,” says Wismer.

Cardiac glycosides in the Christmas rose can cause death by affecting heart rhythm. These compounds affect the contractility of cardiac muscles by binding to Na-K ATPase, an enzyme that modulates intracellular concentrations of sodium and potassium ions. Amaryllis contains alkaloid compounds, such as lycorine. Lycorine inhibits peptide bond formation during protein synthesis by interfering with the peptidyl transferase activity of ribosomes (See Wink, M. et al and Kukhanova, M. et al). These toxins can lead to depression, convulsions and tremors.

The severity of the toxic effects depends on many factors. “One important factor is the plant itself. The toxic amounts in a plant will vary with the species and stress the plant was exposed to during growth,” says Wismer. “Another factor is the size of the animal and the amount of plant ingested — did the cat just nibble a leaf or eat the entire plant?”

In the case of amaryllis, the toxicity varies according to plant part; the foliage and flowers are less toxic than the bulb. Some plants are deadly only to certain pets. For example, true lilies cause kidney failure in cats, while dogs experience only mild stomach upset. The reason for this species difference is unknown.

Not all holiday plants are a cause for concern. Contrary to popular belief, poinsettias (Euphorbia pulcherrima) are not toxic to pets. Research indicates that the pulcherrima species lacks diterpenes, a key toxic substance generally found in the Euphorbia genus.

Despite best efforts to keep pets away from plants, accidental ingestion may happen. In preparation for such an event, Wismer recommends keeping a list of all plants in the household and calling a veterinarian in cases of suspected ingestion.

Holiday plants dangerous for cats and dogs (except one)

“Since many different plants have the same common name, knowing their Latin names can come in handy.”
– Tina Wismer, medical director of the Americasn Society for Prevention of Cruelty to Animals Animal Poison Control Center

Hippeastrum

Amaryllis Amaryllis lily, Belladonna lily, Saint Joseph lily, Cape belladonna, Naked lady Flickr Commons user Drew Avery

Ilex opaca

American Holly American holly U.S. Department of Agriculture

Ilex aquifolium

English Holly English holly Flora von Deutschland, Österreich und der Schweiz (1885)

Helleborus niger

Christmas Rose Christmas rose, Hellebore, Lenten rose, Easter rose Flora von Deutschland, Österreich und der Schweiz (1885)

Euphorbia Pulcherrima (safe)

poinsettia Poinsettia Freepixels.com

Phoradendron flavescens

American Mistletoe American mistletoe The National Geographic Magazine (1917)

Viscum album

English Mistletoe European mistletoe Wikimedia Commons user Vizu

Solanum dulcamara

Bittersweet nightshade Bittersweet nightshade Flora von Deutschland, Österreich und der Schweiz (1885)

Solanum pseudocapsicum

Jerusalem cherry Jerusalem cherry Wikimedia Commons user Taragui
Indumathi Sridharan Indumathi Sridharan earned her bachelor’s degree in bioinformatics in India. She holds a Ph.D. in molecular biochemistry from Illinois Institute of Technology, Chicago. She did her postdoctoral work in bionanotechnology at Northwestern University.