Are Hydrangeas Poisonous to Cats and Dogs?

Considered by many gardening enthusiasts as "grandmother's old-time flower," there's more to the pretty hydrangea than meets the eye.

dog in front of purple hydrangeas
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Bursting with lush bunches of white, blue, red, purple, or pink flower clusters — the color dependent upon the alkalinity or acidity of the soil — it's hard to resist this gorgeous plant that truly amps up your home's curb appeal. But if you have cats or dogs, think twice about planting or displaying them.

Although they're undoubtedly one of the most beautiful flowers, hydrangeas are inedible, and poisonous to cats, dogs, and horses. For this reason, they should not be planted in areas frequented by these animals. Not only are the flowers and leaves poisonous, but all parts of the plant contain toxic cyanogenic glycoside.

Cyanogenic glycosides and symptoms of poisoning

Cyanogenic glycosides are chemical compounds contained in foods that release hydrogen cyanide during the act of chewing or digestion, and lead to the hydrolysis, or enzymatic breakdown of the substances, which in turn causes cyanide to be released. Some of the more common clinical signs of poisoning include:

  • Diarrhea
  • Vomiting
  • Depression

While cyanide intoxication is rare, it usually causes more of a gastrointestinal disturbance. Always contact your veterinarian immediately if you have observed your dog or cat eating or even nibbling on a hydrangea plant, regardless if they are exhibiting any signs of illness.

Hydrangea (Hortensia)
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Are hydrangeas poisonous to cats?

Cats love chewing on plants to the dismay of pet parents, who enjoy cultivating plants and flowers indoors and out. But aside from their cat destroying plants, unbeknownst to many, cats are sensitive to a host of plants, and in some cases, even a tiny amount of the plant matter can potentially cause major illness, says the American Society for the Prevention of Cruelty to Animals.

Hydrangeas are among those that are poisonous. And while chewing or ingesting hydrangea can make your cat sick, Plant Addicts, a plant-supply house in Nebraska, says that eating hydrangeas is rarely fatal if the incident is handled properly, which means, of course, that you contact your veterinarian as soon as possible.

In addition to hydrangeas, the ASPCA says there are more than 25 plants that are also toxic to cats, including the daffodil, gladiola, iris, azalea, calla lily, hyacinth, tulip, lily of the valley, morning glory, wisteria, and other flowering plants commonly found in gardens.

The symptoms of poisoning in cats will depend on the type of plant and how much was consumed, ranging from minor stomach upset to severe kidney failure, and can even be fatal if not addressed in time. Skin irritations and itchiness around the mouth and face are also common signs that a cat has chewed or eaten a toxic substance.

In addition to the basic clinical signs of diarrhea, vomiting, and depression, the following are some of the common signs of plant poisoning in cats:

  • Rapid heart rate.
  • Panting
  • Difficulty breathing caused by inflammation that blocks air passages.
  • Drooling
  • Dilated pupils.
  • When the kidneys are impacted by a toxic substance, it will cause excessive drinking and urination.
dog in front of white hydrangeas
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Are hydrangeas poisonous to dogs?

Dogs and gardens can happily coexist. And planning a dog-friendly garden not only considers the placement of plants — a huge consideration if you have multiple dogs who run around and play together in close proximity to the garden — but also learning which plants and flowers are toxic to dogs and avoiding them.

Dogs are not as likely to nibble on plants as cats, but puppies will put anything into their mouths. Hydrangeas are among the plants that are poisonous to dogs, but as in cats, it's usually not fatal in most cases if handled properly.

You should always contact your veterinarian to seek guidance if you observe the most common symptoms of poisoning such as diarrhea, vomiting, and depression. Other clinical signs of poisoning in dogs from toxic plants are similar to the symptoms in cats and include:

  • Drooling
  • Panting
  • Excessive drinking of water and increased urination.
  • Increased heart rate.
  • Difficulty breathing.

Are dried hydrangeas toxic, too?

Dried hydrangeas make a glorious floral display with the superb vintage-looking blue hues a favorite of many. But are dried hydrangeas poisonous to dogs and cats?

Unfortunately, dried hydrangeas are just as toxic as fresh ones. In fact, all dried flowers can have adverse effects when eaten since they are usually treated with drying agents, glues, dyes, and other toxic substances.

Getting help if your cat or dog is poisoned

If your cat or dog is poisoned, it's essential to get immediate veterinary attention. But what do you do if your vet is not available when you need her? Planning for a medical emergency for your pets is crucial. Keep the phone numbers of local emergency veterinary hospitals close at hand as well as the National Animal Poison Control Center number: 1-888-426-4435.

Hopefully, you will never need to call, but if you do, have the name of the plant or flower ready and how long ago it was chewed or consumed; the two variables that will dictate the treatment protocol.