Smooth Hydrangea

Hydrangea arborescens

Family: Hydrangeaceae

US Native
Cold Hardy
Blooms on New Wood

Pet & Human Safety

People: Not researchedPets: Toxic to pets

People: not researched yet.

Toxic to pets

ASPCA's page (additional common names: Hortensia, Hills of Snow, Seven Bark) states directly: 'Toxic to Dogs, Toxic to Cats, Toxic to Horses,' toxic principle cyanogenic glycoside, clinical signs 'vomiting, depression, diarrhea. Cyanide intoxication is rare: usually produces more of a gastrointestinal disturbance.' NC State independently states this species is 'poisonous to humans, dogs, cats, and horses.' This is the strongest-sourced of the four hydrangea toxicity verdicts in PlotAndPetal, since it's a direct match rather than a whole-genus inference.

PlotAndPetal cannot tell you whether a plant you found can be eaten. Only someone who can see the plant can identify it.

Poison control

If someone has collapsed, cannot be woken, is having a seizure or has trouble breathing, call 911 now. For any other possible poisoning, call Poison Help: 1-800-222-1222.

Emergency number source: U.S. federal law (47 U.S.C. § 251(e)(3)), read 2026-10-07.

Naturalist Lore

Historical Background & Breeding Lore

The history of this plant and its name, and how it was bred, where we have them.

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Care

Hardiness zones: USDA 3a-9b: very cold-hardy but also adaptable to warmer climates, reaching the edge of central Florida (NC State Extension).
Mature size: 3-5 feet tall and wide (NC State Extension): notably more compact than panicle or oakleaf hydrangea.
Where it comes from: Eastern United States, from New York to Florida, west to Iowa, Missouri, Oklahoma and Louisiana; native to moist or rocky wooded slopes, ravines, streambanks and bluff bases (NC State Extension): like oakleaf hydrangea, a species actually native to the Southeast.

Soil & Drainage

Pruning & Flush Rhythm

Feeding Schedule

How to prepare the soil, when and what to feed, and how and when to prune where that applies.

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