Plants to avoid

By Rebecca Jepsen
for the Mercury News
July 4, 2009

With school out and summer in full swing, many of us are enjoying the great outdoors and our own backyards. Since quite a number of commonly used plant species can be harmful for not only adults and children but furry family members as well, it's a good time to take stock of the flora and fauna around you.

If you do have potentially dangerous plants, you can move them to an area less accessible to children and pets.

Or you trim plants up off the ground and out of easy reach, or create barriers using fencing, garden art or other plants. You won't have to worry that a child or pet who is in the habit of putting anything and everything in their mouth will be hurt (though you should always keep a watchful eye on both when they are in the garden, yard or anywhere outdoors).

It is important to be able to identify the plants that may pose problems:

  • For example, I was surprised to learn that my prized sago palm (Cycas Revoluta) can be extremely toxic to dogs and cats. All parts of the plant are poisonous, but the seeds, or "nuts," contain the largest amount of toxin. Serious illness can result from ingesting just one or two seeds, including vomiting, diarrhea, depression, seizures and even liver failure.
  • Oleanders are considered to be one of the deadliest plants in the world; every part of the plant is toxic. The leaves and woody stems contain concentrated amounts of saponins and cardiac glycosides that when ingested Advertisement cause severe digestive upset and heart palpitations that can lead to death.
  • Azaleas and rhododendrons contain grayantoxins, substances that can cause weakness and depression of the central nervous system in humans and pets. Symptoms, when ingested, may include vomiting, drooling and diarrhea. Severe azalea poisoning could lead to coma and death from cardiovascular collapse.
  • Castor bean (Ricinus communis) contains ricin, a highly toxic protein that can produce severe abdominal pain, diarrhea, excessive thirst and loss of appetite in both humans and pets. Extreme cases can result in dehydration, tremors, seizures, coma, and death.
  • Lilies (Lilium) are highly toxic to cats. Severe kidney damage can result from ingesting even a small amount of the plant.
  • Mushrooms can be extremely poisonous, and unfortunately many of them look alike. In general it's best to avoid eating any mushroom that you find in your backyard or the wild unless you are with a professional who knows what they are doing.

Common indoor houseplants are not necessarily safer. Toxic varieties include daffodils, dieffenbachia, elephant ear, philodendrons, peace lily, English ivy, cyclamen and amaryllis.

For more information, or if you suspect your child or pet has ingested any of these poisonous plants, call the California Poison Control System at 1-800-8-POISON as soon as possible.

Knowledge and caution are the keys. The more you know and the more care you take to make sure there will not be problems, the more you can relax in your garden or enjoy being outdoors.

Rebecca Jepsen is a Santa Clara County Master Gardener.