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Everything You Need to Know About Hydrangea Plant Toxicity

If you haven’t experienced the cool summertime beauty of hydrangeas in bloom, well let’s just say you’ve been missing out. And while these shade-loving hedge plants offer a laundry list of benefits for the gardens and gardeners alike, they do have one setback to be aware of: If eaten in large enough quantities, hydrangeas have the capacity to make you or your pets very sick. So what precisely about hydrangeas makes them toxic to most mammals (including humans, dogs, cats, and horses)? We’ll dive into that next. 


Are Hydrangeas Poisonous?

Are Hydrangeas Poisonous?

The short answer is yes, hydrangeas are in fact toxic when ingested by humans or pets. This is because hydrangeas contain a compound called amygdalin, which turns into a form of cyanide when ingested by most mammals, including humans, cats, dogs, and even horses. 

Although it would take quite a bit of hydrangea flower or leaf to produce any adverse effects, some common side effects of cyanide poisoning in humans and pets include: 

  • Vomiting 
  • Nausea
  • Diarrhea
  • Difficulty breathing
  • Loss of appetite
  • Stiffness
  • Abdominal pain
  • Increased heart rate or temperature
  • Seizures 

If you suspect you or your pets have ingested toxic levels of hydrangea flower (or any other garden plant), contact a medical professional immediately. A 24/7 Pet Poison Helpline can be reached by calling (855) 764-7661. 

About Hydrangeas

About Hydrangeas

Hydrangeas are a shade-loving woody perennial that can be found the world over in growing zones 3 to 7. A popular choice in coastal gardens of the Northeast, Hydrangeas will equally thrive in gardens of the west or central United States. Depending on the acidity or alkalinity of your soil, hydrangeas will bloom in a variety of colors: From blues and whites to pinks and even tinted shades of green. 

Like many spring and summer blooms, hydrangeas contain high levels of toxic constituents that can be dangerous if consumed in large quantities. While eating just one petal isn’t likely to threaten your life or well-being, eating a lot of blooms certainly could. Like most things, toxicity in plants is relative to the size of the person or animal ingesting them. Although a petal is unlikely to produce symptoms in a full-size adult, it may be more serious if ingested by a child or small pet. 

The main source of toxicity in hydrangeas is called amygdalin, which is a naturally occurring constituent found in a variety of flowers and seeds, including apple seeds, and the pits of cherries, apricots, and peaches. 

The concern with amygdalin is that it metabolizes into a form of cyanide when ingested. Cyanide poisoning can manifest differently in different mammals, meaning that cats, dogs, humans, or even horses could show various symptoms if they eat a large enough quantity of the plant material. Key things to watch for if you suspect hydrangea poisoning include: Nausea, vomiting, diarrhea, heightened temperature or blood pressure, and seizures. Don’t delay in contacting a medical professional in cases of suspected poisoning. 

Are All Types of Hydrangeas Toxic?

Are All Types of Hydrangeas Toxic?

While the exact levels of toxicity in various types of hydrangeas haven’t been extensively recorded, suffice it to say that all common garden hydrangeas are thought to be reasonably toxic to mammals. No matter what kind of hydrangea you have in your garden, the safest protocol is to keep young children and pets away from them if you think they might try and take a bite. 

Are Dried Hydrangeas Poisonous?

Yes. Much like fresh hydrangea blooms and leaves, dried hydrangeas contain concentrated forms of amygdalin, a cyanogenic glycoside. Commercially preserved hydrangeas sometimes contain other chemicals as well, making them even more toxic if consumed. 

Can you smoke dried hydrangeas?

Can you smoke dried hydrangeas?

The real question here is should you smoke hydrangeas. And the answer is definitely not. Being a toxic plant, smoking the dry leaves or flowers of a hydrangea presumably delivers a toxic dose of cyanide (via amygdalin) which leaves your body deprived of oxygen and the smoker feeling light-headed. According to Nature’s Poison’s, “Inhaled cyanide, in sufficient doses, can cause coma, cardiac arrest, or death within minutes.”

Considering the numerous non-toxic smokable plants out there, this one is best avoided. Consider drying your hydrangeas for a lovely flower arrangement instead. 

What Happens to Your Pets If They Chew or Ingest Hydrangeas?

Although unlikely to be fatal to either cats or dogs, eating any amount of hydrangea buds, flowers, or leaves can lead to signs of toxicity in pets. If you’re concerned your pet may have ingested parts of a hydrangea plant, the best course of action is to contact your veterinarian immediately. 

Tips and Considerations for Safely Handling Hydrangeas

Tips and Considerations for Safely Handling Hydrangeas

Because hydrangeas aren’t toxic unless eaten in large quantities, there’s no reason to be overly careful when handling them. When planting hydrangeas in your garden, the most significant safety consideration is to put them away from small children and pets. Since hydrangeas tend to be border hedges or planted in shady areas at the edge of a garden or up against a house, this should be pretty easy to accomplish. 

When planting, propagating, or transplanting hydrangeas in high-traffic areas (such as long walkways), you might consider adding in a small fence or some other deterrent to keep children and pets out. You can also invest in a pet-safe bitter deterrent spray to discourage your animals from taking a bite. 


Hydrangea Plant Toxicity FAQs: 

How poisonous are hydrangeas to humans?

All parts of hydrangea plants are toxic to pets and humans when ingested, including the leaves, stems, and flowers. Symptoms of hydrangea toxicity include nausea, vomiting, and diarrhea. Seek medical attention immediately if you suspect hydrangea poisoning.

Are all hydrangeas toxic to dogs?

Yes. All garden hydrangeas are toxic to mammals (including dogs and cats) when eaten. Common signs of hydrangea toxicity in dogs include vomiting, diarrhea, nausea, fatigue, loss of appetite, and heightened body temp or heart rate. You should contact your veterinarian immediately if you believe your pet has eaten any part of a hydrangea plant.

Can hydrangea flowers be eaten?

Hydrangea flowers, stems, and leaves should not be eaten under any circumstances since they contain a toxic constituent known as amygdalin which is metabolized into a form of cyanide when ingested by mammals (including humans, cats, dogs, and even horses).

Is there cyanide in hydrangeas?

Hydrangeas contain something called amygdalin, which gets metabolized into a cyanogenic glycoside when consumed by humans, cats, and dogs. Cyanide poisoning is fairly severe, and common symptoms include nausea, vomiting, and diarrhea. Seek medical attention immediately if you suspect cyanide poisoning.


Hydrangea Toxicity- The Final Word

Given their toxic nature, hydrangeas are best enjoyed cautiously and out of reach of small children or curious pets. Although you’d have to eat quite a bit of these blooms to experience dangerous levels of toxicity, this plant is definitely one that’s best enjoyed visually at a distance—and nowhere near your salad bowl.


Author

Larissa is a writer, gardener, and herbalist living in the San Juan mountains of Colorado. Her writing has been widely published in lifestyle and personal finance publications all over the country, and she's also the creator of the weekly newsletter @rootedintribe.

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