Pretty but Poisonous
Published: Tuesday, 03 September 2013 14:46
Written by Maggie Boriski, Brazos County Master Gardener
Poisonous Plants

Poisonous Plants

Are we putting our pets at risk in their own backyards? We create beautiful landscapes to add value to our property as well as for our family’s enjoyment. For many of us, pets are included as part of our families. When evaluating choices of plants or when dealing with existing plants in the landscape, consider the toxic potential of some plant species. While our children can be warned not to handle or ingest certain plants or plant parts, dogs and cats are usually less responsive to our warnings.

Oleander (Nerium oleander) is widely utilized as an ornamental along roadways, in resi- dential areas and home landscapes (particularly for screening). Used because of its dark green, leathery foliage and showy flowers, Oleander is one of the most toxic plants in wide use (2,3).

Oleandrin, the toxic principle in the Oleander plant, is a powerful cardiac toxin. The ingestion of only a few leaves can cause cardiac failure. Clinical signs can be observed within 4 hours of ingestion and may include weakness, hyper-salivation, and abdominal pain and increased (tachycardia) or decreased (bradycardia) heart rate.

Another plant containing a powerful cardiac toxin is the Kalanchoe 3, 4. These flowering succulents are popular in the garden, in containers, and as houseplants. All parts are poisonous but the flower has the highest concentration of the cardiac glycoside referred to as bufadienolides. Depression, hypersalivation, and gastrointestinal signs can begin within a few hours of ingestion and progress to cardiac arrhythmias, rapid heartbeat and respiratory distress. Cardiac arrest is the cause of fatal ingestions.

Lilies belonging to the genus Hemerocallis (including day lilies) and to the genus Lilium (including Easter lilies) also pose poisoning risks to pets, particularly cats 3. These plants contain a toxin, which can result in kidney failure. Lillies are found in gardens or used as houseplants. All parts are considered toxic but the leaves seem to be the most frequently ingested. Clinical signs can develop within 12 hours following ingestion but might not be seen for several days. Vomiting, depression and decreased or increased urination are seen. Seizures, disorientation, tremors and ataxia can also occur in some animals.

Plant toxicity is not limited to these examples. Numerous references list plants toxic to humans and pets 1. Prompt treatment of plant toxicity is critical and often the clinical signs are not specific enough to determine which plant might be involved. So it is important to look for clues should your pet become sick, particularly if the pet has been seen grazing or chewing on plants. Be prepared to provide the scientific names of any suspect plant species or collect samples of plants that appear to have been chewed. This information on plant identity can be critical to ensure proper veterinary treatmeant 3.

[Read about other common poisonous plants and plant partson Aggie Horticulture]


1. Aggie Horticulture Web page. http://aggie- February 7, 2011.

2. Hart, C. R., Garland, T., Barr, A. C., Carpenter, B. B., Reagor, J. C. Toxic plants of Texas. B-6105, 12/00. Texas Agriculture Extension Service. pp 132-133

3. Milewski, L. M. and Kahn, S. A., An overview of potentially life-threatening poisonous plants in dogs and cats. J of Veterinary Emergency and Critical Care 16(1) 2006. pp 25 -33.

4. Smith, Geof, Kalanchoe species poisoning in pets. Veterinary Medicine. November 2004. pp 933-936.