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Toxic to dogs. The ASPCA lists hydrangea as toxic to dogs. Hydrangea is usually a stomach plant in practice: vomiting, diarrhea and a depressed dog, and a call for advice. The cyanide chemistry is why large ingestions, especially by small dogs, are still reported rather than waved off.
Hydrangea is the summer shrub of porches and foundations, mopheads and lacecaps in blue, pink and white, planted exactly where the dog's world is: beside the steps, along the fence, under the windows. The ASPCA lists it as toxic to dogs, cats and horses, and it generates more owner anxiety than its usual effects justify, because the word cyanide travels further than the word rare beside it.
The ASPCA names the toxic principle of hydrangea as A cyanogenic glycoside (hydrangin). Hydrangea carries a cyanogenic glycoside, a compound that can release cyanide when plant tissue is chewed and digested. The ASPCA lists Hydrangea arborescens as toxic to dogs on that basis, and then adds the calibration that defines this page: cyanide intoxication is rare, and the plant much more usually produces a gastrointestinal disturbance. The listed signs are vomiting, depression and diarrhea, and honest treatment keeps both facts in view at once.
The clinical signs the ASPCA lists for hydrangea are: vomiting, depression and diarrhea (the ASPCA notes true cyanide intoxication is rare). The realistic case is a dog that chews leaves or strips a low flower head and is sick within hours, with vomiting and diarrhea and a flat mood, settling over a day with advice from a poison line. The cyanide pathway needs a substantial dose of chewed tissue to matter, which is why the ASPCA frames it as rare; the cases that justify urgency are the small dog that ate a large amount, or any dog whose depression deepens rather than lifts. Dried flower heads, kept for arrangements, shed petals and florets indoors across the winter.
Most dangerous part: Leaves and flower buds carry the glycoside. A flowering shrub offers both in quantity at dog height, and dried flowers drop into the bed below it.
Soil and color are a distraction worth dismissing in one breath: the famous blue versus pink chemistry of hydrangea is about aluminum and pH for human gardeners, and it changes nothing about the plant's listing for dogs. Judge the shrub by its genus and its signs, not its color. When you report a case, the useful facts are amount eaten, which part, and the dog's weight, the same facts as every other page in this section.
Call your veterinarian, the ASPCA Animal Poison Control Center on (888) 426-4435, or the Pet Poison Helpline on (855) 764-7661 right away, even if your dog looks fine. Some poisons take hours or days to show their worst effects. Do not make your dog vomit unless a veterinarian tells you to, and keep the packaging, a photo, or a sample of what was eaten to show the clinic.
Plant new hydrangeas behind other shrubs or fence the bed's edge if your dog is a leaf chewer, and pick up fallen flower heads through the season. Keep dried arrangements where their shedding cannot reach the floor in dog rooms. For a shrub already established, supervision during the puppy months usually carries the dog past the chewing stage.
For a flowering foundation shrub, verify candidates on the ASPCA list by scientific name; the ASPCA lists several viburnum and rose options among plants to check, and the genus level check is the deciding step. Whatever you plant next, check it on the toxic plants index approach: confirm the plant on the ASPCA toxic and non-toxic list under its scientific name, Hydrangea arborescens is the name to avoid here, before it goes in the ground or on the shelf.
Yes. The ASPCA lists hydrangea (Hydrangea arborescens) as toxic to dogs. Its toxic principle is A cyanogenic glycoside (hydrangin), and the signs it lists include vomiting, depression and diarrhea (the ASPCA notes true cyanide intoxication is rare).
Call your veterinarian, the ASPCA Animal Poison Control Center on (888) 426-4435, or the Pet Poison Helpline on (855) 764-7661 straight away. Note what part of the plant was eaten and roughly how much, keep any remaining plant material to show the clinic, and do not make your dog vomit unless a veterinarian tells you to.
Leaves and flower buds carry the glycoside. A flowering shrub offers both in quantity at dog height, and dried flowers drop into the bed below it.
Plant new hydrangeas behind other shrubs or fence the bed's edge if your dog is a leaf chewer, and pick up fallen flower heads through the season. Keep dried arrangements where their shedding cannot reach the floor in dog rooms. For a shrub already established, supervision during the puppy months usually carries the dog past the chewing stage.
It contains a cyanogenic glycoside, which can release cyanide, but the ASPCA states that cyanide intoxication from hydrangea is rare and that gastrointestinal upset is the usual outcome. Both halves of that sentence matter.
That matches the usual listed picture. Offer water, note how much was eaten, and call your veterinarian or a poison line; escalating depression or repeated vomiting should be seen the same day.
This page is general information drawn from the published guidance of the organizations listed under Sources below. It is not veterinary advice, and it does not replace your own veterinarian, who knows your dog. If your dog has eaten something toxic, contact your veterinarian, the ASPCA Animal Poison Control Center on (888) 426-4435, or the Pet Poison Helpline on (855) 764-7661 straight away. A consultation fee may apply on the helplines.
Last updated: November 2026. Every verdict on this page was checked against the sources listed above. How we work: our methodology.
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