Plants toxic to cats

What actually happens

Terpenoid saponins are detergents. They break down cell membranes on contact, which irritates everything from the mouth down, and the tuber holds far more of them than the leaves and flowers do. That single fact is the whole risk assessment for this plant: a nibbled petal and a dug-up tuber are not the same event.

Toxic principle: Terpenoid saponins

Which parts: All parts, concentrated in the tuber.

The signs, in the order they appear

1. Salivation
2. Vomiting
3. Diarrhea
4. Heart rhythm abnormalities after large ingestions of the tuber
5. Seizures
6. Death

How fast: Drooling and stomach signs are the usual course. Heart rhythm abnormalities and seizures are documented after large quantities of tuber, and are described as uncommon.

How to recognize it

Flowers with petals swept sharply upwards, as though caught in the wind, on bare stalks above heart-shaped or kidney-shaped leaves that are usually marbled with silver. A winter pot plant across all four of our markets.

What actually happens

Lycorine is an emetic: it makes an animal sick, and in small exposures that is most of what happens. The bulb is a different proposition, holding the alkaloids in concentration alongside crystals that irritate on contact. Bulbs are the part stored in a garage or a cupboard over winter, which is exactly where a cat can find one loose.

Toxic principle: Lycorine and other alkaloids

Which parts: All parts. The bulb is the most poisonous, which matters because bulbs are stored where a cat can reach them.

The signs, in the order they appear

1. Vomiting
2. Salivation
3. Diarrhea
4. Convulsions after large ingestions
5. Low blood pressure
6. Tremors
7. Cardiac arrhythmias

How fast: Vomiting, drooling and retching are the usual picture. Pet Poison Helpline notes that large amounts, and bulbs in particular, can bring on low blood pressure and weakness.

How to recognize it

Six petals behind a protruding central trumpet, one flower to a stem, above flat strap-shaped leaves. Yellow is the familiar form, but white and cream are just as common and just as toxic.

What actually happens

Bufadienolides are heart-active molecules, chemically close to the toxin a toad secretes, and that sounds far worse than the usual outcome. Pet Poison Helpline is clear that in cats and dogs the result is most often an upset stomach, with rhythm changes, weakness and collapse reserved for a large ingestion. Both halves of that sentence matter: the risk is real and it is not the likely case.

Toxic principle: Bufodienolides

Which parts: All parts.

The signs, in the order they appear

1. Vomiting
2. Diarrhea
3. Abnormal heart rhythm, rarely

How to recognize it

A compact succulent with thick, scalloped, glossy leaves and dense flat-topped heads of small flowers in yellow, orange, pink or red. Sold everywhere as a supermarket pot plant in winter.

What it gets confused with

• Mother of thousands and mother of millions

  Different Kalanchoe species, sold under those names, which grow plantlets along the leaf edges.

  Why it matters: Pet Poison Helpline lists them under the same entry. Those dropped plantlets root everywhere, which spreads the plant into places nobody chose to put it.

What actually happens

The name calcium oxalate suggests a chemical burn. It is closer to a mechanical one. The leaves carry specialised cells called idioblasts, packed with bundles of needle-sharp crystals held in a gel. Chewing bursts those cells, the gel swells, and the pressure fires the needles out with real force. They go on firing after the bite, down the throat and into the stomach, which is why the pain does not stop when the mouthful does. A proteolytic enzyme in the same sap then triggers a histamine release, so the tissue swells as well as being punctured. That swelling, and not the toxin, is what can turn this from painful into dangerous.

Toxic principle: Insoluble calcium oxalates, proteolytic enzyme

Which parts: Sap and leaves.

The signs, in the order they appear

1. Oral irritation
2. Intense burning of mouth, tongue and lips
3. Excessive drooling
4. Vomiting
5. Difficulty swallowing

How fast: Fast. Drooling and trouble swallowing come on rapidly, which is the one mercy here: the pain is immediate, so a cat almost always spits the mouthful out before swallowing much of it. Watch the swallowing and the breathing over the next few hours, and call your vet if either changes.

How to recognize it

Large oval leaves, dark green with broad cream or yellow markings down the center, growing from thick upright canes. One of the commonest office and living-room plants.

What it gets confused with

• Philodendron

  Both are aroids with the same crystals, and young plants of each are sold in similar pots.

  Why it matters: Here the confusion is harmless: same mechanism, same verdict, same advice. Not every look-alike pair is a trap, and saying so is part of the job.

What actually happens

The whole difficulty with this plant is its name. Pet Poison Helpline, the one poison service that publishes a dedicated entry for the true crocus, records drooling, vomiting, loss of appetite and diarrhea, and goes out of its way to say that spring-blooming crocuses are not to be confused with the autumn crocus, which causes severe kidney and liver injury. The ASPCA's plant database has no entry for the true crocus at all, which is a silence and not a verdict, so this page rests on a single named source and says so. What is not in doubt is the botany: Crocus belongs to the iris family, Colchicum to a different family entirely, and the saffron of cooking comes from a true crocus.

Toxic principle: Not named by the sources we accept. Pet Poison Helpline describes the effects without identifying the compound.

Which parts: Not broken down by part in the source. Bulbs are the part left within reach in sheds and cupboards over winter, as with any garden bulb.

The signs, in the order they appear

1. Drooling
2. Vomiting
3. Loss of appetite
4. Diarrhea

How fast: Stomach signs. If your cat is unwell after eating any plant, describe what it was and when, and let your vet decide whether it matters. The urgent question with a crocus-shaped flower is which plant it actually was.

How to recognize it

Count the stamens. A true crocus has THREE, a colchicum has SIX with orange anthers. That is the one test that works, and it works in any season. The second tell is the leaves: crocus leaves, narrow and grass-like with a pale central stripe, are present while the flower is open, whereas a colchicum flowers out of bare ground with no leaves at all, which is where its name naked ladies comes from. Both grow from corms and both hold their flower stem underground.

What it gets confused with

• Autumn crocus

  They look alike, share the word crocus, and both push a goblet-shaped flower straight out of the ground. They are not related: different families, different chemistry.

  Why it matters: This is the confusion that kills, and it runs the dangerous way round. Mistaking a colchicum for a crocus turns a lethal plant into a reassurance. Count the stamens: three is a crocus, six is a colchicum.

• Saffron crocus

  Crocus sativus is a genuine crocus that flowers in AUTUMN, and it is also sometimes called autumn crocus. Meanwhile the deadly Colchicum autumnale is commonly called meadow saffron and is not the source of saffron at all.

  Why it matters: The season rule that most lists give you, autumn means deadly, is not safe. Two harmless true crocuses bloom in autumn and one lethal colchicum is named after saffron. The names have been swapped in every direction; the stamens have not.