At a glance
| Plant | Hydrangea (Hydrangea arborescens (ASPCA’s entry); Hydrangea macrophylla (bigleaf)) |
|---|---|
| Cats | Toxic |
| Dogs | Toxic |
| Toxic principle | a cyanogenic glycoside |
| Signs ASPCA lists | vomiting; depression; diarrhea |
| ASPCA page | Hydrangea, checked November 10, 2026 |
What else to know
ASPCA’s hydrangea entry names one species, smooth hydrangea (Hydrangea arborescens). The common blue-or-pink bigleaf hydrangea (H. macrophylla) isn’t listed on its own, so Plamp marks it “not verified” rather than guess.
NC State’s profile for bigleaf hydrangea lists the same kind of compound (hydracyanosides, a cyanogenic glycoside) at low poison severity.
Look-alikes
The plants it’s most often confused with have the same verdict on ASPCA’s list.
Care basics
Light: Dappled sun to shade, out of the afternoon sun (bigleaf hydrangea).
Soil and water: Well-drained soil, though occasionally wet ground is fine. Flower color follows the soil: blue in acidic soil, pink in alkaline. Prune before August 1.
Source: NC State Extension Plant Toolbox: Hydrangea macrophylla.
If your pet ate some
Call your vet, or ASPCA Animal Poison Control at (888) 426-4435, as soon as you can. ASPCA runs the line 24 hours a day, every day of the year, and says a consultation fee may apply.
Call (888) 426-4435 · ASPCA Animal Poison Control
This page is reference information, not veterinary advice. Toxicity facts are summarized in our own words from the ASPCA Toxic and Non-Toxic Plants list; Plamp is not affiliated with the ASPCA.
