Boxwood

What it does to a cat.

Boxwood is toxic to cats. The ASPCA lists Buxus spp. as toxic to cats, dogs, and horses. The toxic principle is buxine alkaloids — a class of steroidal alkaloids present throughout the plant in leaves, stems, and bark.

The ASPCA's verdict, verbatim: Scientific Name: Buxus spp. · Family: Buxaceae · Toxicity: Toxic to Dogs, Toxic to Cats, Toxic to Horses · Toxic Principles: Alkaloids · Clinical Signs: Dogs and cats: vomiting, diarrhea; Horses: colic, diarrhea. The verdict is genus-wide — Buxus sempervirens (common boxwood / English box), Buxus microphylla (Japanese / Korean box), and the named cultivars are all covered.

Why boxwood matters more than most toxic plants

Most toxic houseplants get into a cat's life because someone bought one and put it in the living room. Boxwood is different: it's the most-planted hedge shrub in suburban America. Every property line, every corporate landscaping bed, every formal garden has it. An indoor-outdoor cat or a cat who escapes onto the porch walks past more boxwood foliage in a week than they'll meet of any houseplant in a year.

The toxin is mild — vomiting and diarrhea, resolving in a day or two — and that's the second reason it doesn't get the attention it deserves. There's no dramatic clinical sign. A cat that grazes the hedge on the way home is sick the next morning, the owner doesn't connect the dots, and the cat goes out again. Repeat exposure is the realistic harm pattern.

What it does to a cat

• Vomiting (most common): onset 1 to 4 hours after ingestion. Self-limiting in light grazing.
• Diarrhea: often follows vomiting. 24–48 hour course.
• Anorexia: cats may refuse food for a day after a moderate dose.
• Cardiac effects (very rare): the steroidal-alkaloid mechanism can produce cardiac signs at high dose. Documented in horses (which eat much larger quantities of hedge); rare in cats.

If your cat is lethargic for more than 24 hours, dehydrated, or shows any neurological or cardiac signs, go to the vet. Call the ASPCA Animal Poison Control Center at 888-426-4435 for dose-based guidance.

The clippings trap

A specific risk worth flagging: boxwood hedge clippings. Trimmed boxwood foliage is more accessible than the standing hedge — cats can graze a pile dumped at the back of a bed without having to push past the dense outer leaves. If you have outdoor cats or wandering neighbour cats, bag clippings and bin them. Do not compost in an accessible heap.

Cat-safe alternatives to a boxwood hedge

The "formal evergreen hedge" role is hard to substitute on the ASPCA non-toxic list — most candidates (yew, holly, privet, laurel) are also toxic. Options that work at smaller scales:

• Rosemary for a low informal hedge — ASPCA-safe, clips well, aromatic.
• Lavender for a low scented edge.
• Bamboo (true bamboo, Bambusoideae) is ASPCA non-toxic and works as a tall screening hedge in the right zone — but check the species, since some so-called "bamboos" (sacred bamboo, Nandina) are toxic and unrelated.
• Catnip for a wilder garden border at planting-bed scale.

For the full toxic-plants reference, browse the toxic plants list.