Which plants are poisonous to cats, and which are safe?

True lilies (the genus Lilium: Easter, tiger, stargazer, rubrum and Japanese show lilies) and day lilies (Hemerocallis) can cause acute kidney failure in cats. This is the best-known plant danger for cats.

Every part is dangerous: flower, stamens, leaves, stem, roots, pollen and the water in the vase. A cat can be poisoned by chewing a leaf, by licking pollen off its own fur after brushing past a flower, or by drinking vase water. Dried and dead parts stay toxic, and taking the pollen-bearing parts off a flower does not make it safe.

Cats seem to be unusually sensitive to lilies. Dogs mostly get a mild upset stomach from the same plants. The toxin has not been identified, and how badly a cat is hit cannot be predicted from the amount.

Early signs often start within hours: vomiting, drooling, tiredness and not eating. They can ease for a while, but the kidneys may still be failing. Increased thirst and urination, and later little or no urine, follow over the next one to three days.

Treat any possible lily contact as an emergency, even if the cat looks fine. Care that starts early gives the best chance. A delay of about 18 hours or more generally leads to kidney failure.

There is no antidote. Vets commonly give intravenous fluids for days and check blood and urine repeatedly. Hospital stays of several days are usual, and some cats need dialysis. Even with treatment some cats die or are left with lasting kidney damage.

Not everything called a lily causes the same illness. Peace lily (Spathiphyllum) and calla or arum lily (Zantedeschia) contain oxalate crystals that irritate the mouth. Lily of the valley affects the heart. Gloriosa (flame) lily can cause organ failure. Peruvian lily (Alstroemeria) is the mildest. None of them is safe, so check any plant with lily in its name.

Sago palm (Cycas) is among the most dangerous houseplants. All parts are toxic and the seeds most of all. It mainly damages the liver, and any suspected bite is an emergency. Most reported cases are dogs, but the warning holds for cats.

Dieffenbachia (dumb cane), monstera, philodendron, pothos and peace lily contain calcium oxalate crystals. They burn the mouth and cause drooling, pawing at the mouth and vomiting, and swelling can make swallowing or breathing hard. Most bites are mild to moderate, but a swollen tongue or throat is an emergency.

Kalanchoe is a common gift plant with heart-acting toxins in all parts, most in the flowers. Ivy (Hedera), cyclamen and ficus can cause drooling, vomiting and diarrhoea or skin irritation, and cyclamen tubers are more dangerous.

Aloe vera is named as poisonous to cats by several consumer sources (stomach pain, drooling, diarrhoea); check the exact plant in the ASPCA list. Yucca, croton and caladium also appear on insurer toxic lists. Amaryllis, mainly the bulb, can cause drooling, vomiting and tremors, and even the vase water can make a cat ill.

Oleander (Nerium) is poisonous in all parts, including sap and the water a cut branch has stood in. It disturbs the heartbeat and can be fatal. Smoke from burning oleander is also dangerous.

Yew (Taxus) is poisonous in all parts except the red fleshy fruit and can cause collapse of heart and circulation. Fresh clippings left in a garden are an extra risk. Azalea and rhododendron contain grayanotoxins that affect heartbeat and blood pressure, even in small amounts. Foxglove (Digitalis) also affects the heart.

Autumn crocus (Colchicum) is very toxic in all parts, especially the corms and seeds. It causes vomiting, diarrhoea, drooling and collapse, and can lead to kidney failure and death. Do not confuse it with spring crocus.

Daffodil (narcissus) bulbs can cause drooling, vomiting, belly pain and heart rhythm changes. Tulip and hyacinth bulbs are the most toxic part and cause drooling, vomiting and diarrhoea. Hydrangea, arum lily, gladiolus, chrysanthemum and tomato leaves and green fruit are also on toxic lists and can cause vomiting, drooling and diarrhoea. Call a vet after contact with a bulb.

Florists often mix lilies into bouquets without saying so. Check every bouquet and take out lilies, or ask the florist or the sender for a lily-free arrangement. Also take out lily of the valley, amaryllis, daffodils, tulips and chrysanthemum.

Vase water can carry pollen and toxins. A cat that drinks from a vase of lilies, amaryllis or lily of the valley can be poisoned. Keep vases where a cat cannot get to them, or choose safer flowers. Wedding bouquets and keepsake arrangements with lilies stay dangerous even when dried.

Roses, gerbera, sunflowers and asters are listed as safe garden or cut flowers for cats. Roses can still scratch with thorns, and any plant can upset the stomach if a cat eats a lot.

Poinsettia is often feared more than it deserves. Its milky sap irritates the mouth and stomach and usually causes vomiting, poor appetite and low mood. Sources disagree on how strong this is (Cornell lists it as toxic, Penn Vet calls the danger exaggerated), so treat a bite as a reason to call the vet. Sap on skin or in the eyes irritates.

Mistletoe berries are the most toxic part. Vomiting, poor appetite and dehydration are the main problems, and very young or old cats may need treatment. Holly leaves and berries cause vomiting and diarrhoea, and the spines can hurt the mouth. This can be worse than from poinsettia or mistletoe.

Real Christmas trees: one consumer programme says the needles are toxic and your cat can swallow them if the tree stands near the food bowl. The water in the tree stand is not good for your cat either. Needles are not a major poison but can upset the stomach and scratch. Do not leave tree water where a cat can drink it, since it can carry fertiliser or preservatives.

Tinsel and ribbon are not poisonous, but a swallowed piece can block the gut. This is not covered by the plant sources we read, so ask your vet. Lilies are popular around Christmas and Easter: check gifts and arrangements before they come in the house.

Safe houseplants named by veterinary and consumer sources: spider plant, Boston fern, African violet, calathea, prayer plant (maranta), Norfolk Island pine, areca and parlour palm, orchids (Phalaenopsis), Christmas cactus, most cacti, burro's tail and hen and chicks.

Safe herbs and grasses: cat grass (oats, barley or wheat), catnip, thyme and parsley. Choose cat grass with soft blades. Cat grass is a good place to point a cat that likes to chew leaves.

Safe does not mean the cat may eat unlimited amounts: any plant material can cause vomiting or loose stools if a cat eats a lot. Plants listed as non-toxic or mildly irritating are not expected to be life-threatening. The ASPCA list is the standard place to check a plant by its full name, but it is not complete, and a plant can look different from its photo.

Names confuse. Pelargonium is toxic but hardy garden geranium is not. Many plants sold as palms are cycads. “Kamerpalm” (houseplant palm) can mean different plants, so check the Latin name on the tag.

Move the cat away from the plant and keep it calm and warm. Call your vet or the nearest emergency vet straight away, even if the cat seems fine. With lilies, sago palm, oleander, yew, autumn crocus and azalea, do not wait for signs.

Take a photo of the plant, or a sample in a sealed bag, and write down the plant name, which part, roughly how much and when. Use the Latin name if you can: common names differ by region.

Do not make the cat vomit at home. For some plants vomiting is advised, for others it makes things worse, so only a vet decides. Do not give milk, salt water or food unless the vet says so. A vet will decide on fluids, monitoring and blood tests based on the plant, the time since and your cat. Liver or kidney damage can show only one or two days later, so follow-up checks matter.

The safest rule with lilies: no lilies in a home with a cat. Cats jump, leaves fall, vases spill and pollen travels, so out of reach is not enough. Tell visitors and anyone who sends flowers that lilies are dangerous to cats. Kittens and bored indoor cats are the typical cases.

Check the plant name before you buy, and ask the garden centre or florist for the scientific name if the tag does not have it. Keep plants on high shelves, in hanging planters or in a room the cat cannot enter. Offer cat grass as a safe alternative.

Keep cats indoors or in a secure outdoor enclosure if the garden has lilies, yew, oleander or azalea, and keep garden clippings out of reach. Do not use cocoa shell mulch, which contains theobromine, and do not use poisons or cleaners in the garden that a cat can pick up on its paws or coat.