Seven bark is a common shrub or bush in the same genus as the hydrangea, but it is a wild variety that originates from the eastern United States. In the wild, it is most often seen growing in large groups and can reach up to 10 feet tall and 5 feet wide. The evergreen leaves are large and oval, with stem bark that comes off in layers, which is why it is called seven bark. The flowers are big round groups of tiny white flowers, similar to the blooms of baby’s breath.

The seven bark plant (also called smooth hydrangea) contains two dangerous substances, which are hydrangin and saponins. If your pet eats any part of this dangerous shrub, chances are high that you will see symptoms within a few hours of consumption. Some of the most common signs of seven bark toxicosis are severe gastroenteritis, irregular heartbeat, and even convulsions leading to death. Hydrangin is a cyanogenic glycoside used in making cyanide and is a natural insect repellent for the seven bark plant, but it can create havoc to your pet’s system if eaten.

The side effects of seven bark poisoning vary greatly depending on what part of the plant is eaten and how much your dog consumed. With more than one type of toxin, it is possible for your pet to only show the signs of one and not the other, but most often have symptoms of both. 

The botanical name for seven bark is Hydrangea arborescens and it is from the Hydrangea genus of the Hydrangeaceae family. This pretty shrub is also known by several other names, including:

Seven bark poisoning is caused by the consumption of any part of a seven bark plant due to the toxic components:

When you arrive at the veterinary clinic or hospital, be prepared to tell the veterinarian everything you know about what your dog ate and how much. Also, it helps if you bring a photograph or sample of the plant for identification. Tell the veterinarian what symptoms your dog has shown and if you have given your pet any medication, vitamins, or supplements lately that may interact with potential treatment. This knowledge is also essential to diagnosis because some drugs may hide symptoms or have side effects that do not fit with seven bark poisoning. 

The veterinarian will do a comprehensive physical examination, including pulse ox (oxygen level), blood pressure, weight, reflexes, pupil reaction time, body temperature, heart rate, and breath sounds. Afterward, she will probably want to do an endoscopy, which is done by using an endoscope to examine your dog’s throat and esophagus to determine if there are any plant particles or other foreign material that need to be removed. Your dog will be sedated during the procedure for safety and comfort. Urine and stool samples will be taken at this time for microscopic examination. Some other necessary laboratory tests may include liver panel, glucose levels, complete blood count (CBC), blood urea nitrogen (BUN), blood chemistry, and packed cell volume (PCV). Also, x-rays (digital radiographs) are usually performed to check for intestinal obstructions and an ultrasound is helpful in determining if the liver, kidneys, or other vital organs are damaged or have signs of inflammation. In addition, an MRI or CT scan may be done for a better look of the damage.

There is an antidote for seven bark poisoning, but it has to be administered before any symptoms begin, so it is usually not used. The best way to treat your dog for toxicity is with evacuation, decontamination, medication, and observation.

The veterinarian can induce vomiting by giving your pet an emetic, such as ipecac or hydrogen peroxide. Also, charcoal will be given by mouth to absorb any undigested toxins.

Intravenous (IV) electrolytes and fluids will be administered to flush the kidneys. This step also rehydrates your dog’s system.

The veterinarian may give your pet sodium nitrite or thiosulfate, oxygen therapy, antacids, H2 blockers, and an antiemetic to control vomiting.

Your dog will most likely be hospitalized for 12 to 36 hours for observation, depending on how much your dog ate and how the treatment is working.

The prognosis may be guarded unless you were able to obtain treatment for your pet  within a few hours of consumption. Any longer than that and the toxins may have already begun to affect the cells and cause irreversible damage to the liver and other vital organs. If your veterinarian believes your pet is fatally ill, it may be more humane to euthanize rather than have your loved one go through the pain of liver failure and other complications.