Mistletoe
Phoradendron flavescens
Mistletoe is toxic to cats per the ASPCA. The phoratoxin and viscumin lectins inside cause vomiting, low blood pressure, and difficulty breathing — a Christmas tradition with a real veterinary risk.
Plate IPhoradendron flavescens — American mistletoe. A parasitic plant on oak and other hardwoods; arrives in December, leaves drop on the floor, cats notice the berries.
Three plants that look the part, without the risk.
Seasonal greenery for a cat-safe Christmas — these three give the same red-and-green festive feel without phoratoxin or grayanotoxin.
Christmas Cactus
Brilliant red and pink blooms exactly when mistletoe arrives. ASPCA non-toxic and lives for decades.
Boston Fern
Lush dark-green foliage that reads festive in any season. ASPCA non-toxic.
Orchid
White or red blooms for a holiday vase. ASPCA non-toxic and lasts for months.
What it does to a cat.
Yes — mistletoe is toxic to cats. The ASPCA lists American mistletoe (Phoradendron flavescens) as toxic to cats, dogs, and horses. The toxic principles are phoratoxin and viscumin — lectins that cause vomiting, low blood pressure, and at higher doses respiratory distress.
It rarely kills pets, but it lands in homes during the one season cats are most likely to encounter it: hung in doorways in early December, dropping berries and leaves underfoot for weeks afterward.
Why it matters more in December than any other month
Mistletoe is a seasonal household plant in a way that very few toxic plants are. It arrives at the same time as poinsettias, holly, and cut Christmas trees — the four highest-volume pet poison-control call categories of the entire year. The berries are small, pearlescent, and irresistible to cats. They drop without ceremony onto the floor where the cat patrols.
The most concentrated source of lectins is the berries; the leaves are also toxic but less so. European mistletoe (Viscum album) is in the same toxin family and is treated identically in clinical practice.
What the lectins do
Phoratoxin and viscumin disrupt protein synthesis at the cellular level and act on cardiovascular tone. The clinical picture in cats is usually GI — vomiting and diarrhea within hours — with cardiovascular signs (low blood pressure, weak pulse, slow heart rate) in more serious exposures. Reports of fatal mistletoe poisoning in cats are rare but exist, particularly with concentrated extracts or high-volume berry ingestion.
What to do if your cat ate mistletoe
Call a vet, especially if berries were involved. Most cases that involve a leaf or two resolve with supportive care, but berry ingestion warrants monitoring for cardiovascular signs. Bring a sample. ASPCA Animal Poison Control is available 24/7 at (888) 426-4435.
Cat-safe substitutes for the season
For a holiday plant that blooms in December without phoratoxin, Christmas cactus (Schlumbergera) is the obvious swap — ASPCA non-toxic and lives for decades. Boston fern covers the festive-greenery role; orchids fill the white-or-red flower role for a centrepiece.
For the other seasonal hazards we cover, see our holly, poinsettia, and christmas cactus pages — the December plant census in one place.
What we have actually seen.
Vomiting and diarrhea
First and most common sign. Cats that swallow berries usually vomit within a few hours.
Low blood pressure
Phoratoxin and viscumin act on cardiovascular tone. Cats may present lethargic, with weak pulse and pale gums.
Difficulty breathing
With high-dose ingestion, respiratory distress and abnormal heart rhythm can follow within hours.
Slow heart rate
Less common than expected for a "cardiotoxic" plant, but bradycardia is documented in serious exposures.
- ASPCA Animal Poison Control Center. Toxic and Non-Toxic Plants: Mistletoe "American".Accessed June 2026 · aspca.org · Toxic Principles toxalbumin, pharatoxin viscumin (lectins, phoratoxins)
- Pet Poison Helpline. Mistletoe (Phoradendron and Viscum) toxicity in companion animals.Clinical reference · 2024
- Merck Veterinary Manual. Mistletoe (Phoradendron) toxicosis.Standard small-animal toxicology reference