Hanging plants safe for cats exist, but the two most common trailing plants are not among them: every plant below is graded S0 Safe for cats against ASPCA or Pet Poison Helpline records, while pothos and heartleaf philodendron — the vines people actually hang — are both S2 Irritant. That is why this list is short and specific. Not one trailing plant in our index is S0; the safe hangers are all leafy or beaded rather than vining. Five below are safe to have swinging over a cat's head — spider plant, Boston fern, hoya, burro's tail, and a Christmas cactus in a basket — with no toxic principle on record for any of them. The three that people hang and shouldn't, including the fern that isn't one, are covered further down.
The two vines people hang most — pothos and heartleaf philodendron — are both S2 Irritant: insoluble calcium oxalate crystals that burn the mouth on chewing. And the feathery asparagus fern sold on the same shelf as the Boston fern above is S2 Irritant too — not a true fern at all, with berries that cause vomiting and skin contact that causes dermatitis. A dangling stem is the easiest thing in the room to bat and chew.