Begonia - Toxic to cats!

Begonias – How to safely showcase these potentially toxic, but definitely beautiful, plants

Safe Or Not?

NOT! The sap of begonias can be toxic or irritating to nearly everything, including humans.

There are few flowers as recognizable and beautiful as begonias. From a distance, some of them – like the Begonia Reina (begonia x hiemalis) pictured here in my makeshift potting bench – look to me like miniature roses, and the color and bounty of blooms they put out in the spring and early summer really perks up any landscape.

Begonia - Toxic to cats!
Begonias – Toxic to cats!

A blooming begonia adds a bright welcome to any home, and up here in the north where our lawns will still be brown and covered with winter’s detritus for a few more weeks it can transform a drab and sad front lawn into a welcome, bright, and colorful home. Begonias grow well in containers, and depending on the variety may tolerate full sun or total shade.

Planting And Care

Read the plating recommendations for your begonias carefully before potting them or placing them in your yard, because they do cover a wide range of conditions, but they are fairly hardy in most conditions.

I find that begonias seem to do best in partial shade, especially on a west side of the house so that they don’t get any full noon sun, and the common wisdom is that any temperatures over 80°F are quite bad for them. So – if it’s hot where you are, shade with perhaps some morning or evening sun to help them dry out each morning or evening would be best.

Allow a fairly large pot for them – 10″ or larger seems to keep them happiest (although as in the picture above they also seem to be ok with very small pots, if you are very careful with the watering). Having a good draining soil for them is very important, so I use a 50-50 mix of potting soil and sphagnum moss to help make sure that the roots have access to water, but aren’t sitting in it.

These plants are particularly sensitive to water on their leaves, so always water them around the base of the plant, and avoid watering them at night if at all possible – they like to go to sleep with no more than a moist bed.

I’ve read that a feeding them with a 15-30-15 fertilizer every month is helpful in getting them to bloom, but I’m a lazy gardener and have found that just adding a little Miracle Gro to their water every other week seems to be both efficacious and fairly painless both for me and the plant. If you do add fertilizer to the water, remember to be careful to not get any water on the leaves.

However – no matter how beautiful they are, we never have begonias in our house.

We plant our begonias outside, in containers or hanging pots, and keep them well up and away from ourselves and companion animals. Here’s why.

Toxicity Information


In cats and many small mammals including dogs, ingesting begonias usually results in an intense burning sensation in the mouth that can lead to irritation of the throat and stomach. Vomiting and excessive salivating,  plus swelling of the lips and tongue can develop. The degree of irritation ranges from mild to severe depending on how much of the plant the animal consumes. Severe cases may prevent cats and other animals from being able to eat. Age and the overall health status of the animal may  potentially cause complications.

All parts of the plant are dangerous, but the tubers and stems contain the greatest concentrations of the toxins. Horses and livestock are more likely to be affected due to the large quantity of plant material they can consume.

Exposures of cats and other animals to begonias should be investigated by a veterinarian. Toxicology veterinarians are standing by 24 x 7 for your poisoning questions at Pet Poison Helpline (800-213-6680; a modest fee applies. Disclaimer: Dr. Kia Benson is an employee of Pet Poison Helpline).


The sap of begonias contain needle-shaped crystals of calcium oxalate called “raphides– the same stuff that forms most of the bulk of kidney stones in humans. One study found that as much as 6% of the plant’s dry weight can consist of these crystals. Like tiny shards of fiberglass, these crystals cut and destroy cell boundaries, including skin cells or the linings of digestive tracks if eaten.

If eaten, the crystals embed themselves in internal tissues and break down into oxalic acid, which is a powerful irritant. This can cause vomiting and excessive salivating as the body tries to purge or dilute the irritant.

All parts of the plant contain these crystals, but the tubers and stems are particularly dangerous.

Most cases of begonia poisoning in cats are mild to moderate and result in side effects such as vomiting and excessive salivating. Older cats may be at greater risk for dehydration and other complications such as secondary kidney failure if their fluid losses are severe or if they are not able to eat for several days.

Horses and livestock ingesting large amounts of the plant may consume enough to cause systemic toxicity – bloody diarrhea, kidney failure and low calcium levels can result leading to serious injury or death.

Even in humans, getting the sap on your hands can cause itching and swelling (dermatitis).

Despite the toxicity of the plant, some people eat the flowers – they are edible, and add a tartness. The flowers have also been used to treat fevers and other diseases.

How we integrate begonias into our lives

Although they can be toxic to our cats and their sap can be as irritating as a kidney stone, begonias are such a beautiful and bright flower that we love to have a couple of them in our landscape, so we just make sure that we are handling and presenting them in the safest possible way and always wash our hands thoroughly after handling them.

Working with begonias either bare-handed or with normal cloth gardening gloves always leaves me feeling like I’ve been handling nettles, so when translating or pruning begonias I always wear rubberized gloves. Despite the gloves, after working with begonias I always wash my hands with soap and water before touching my feline friends.

We don’t want to risk our cats or the neighbor’s pets to be getting into them, so we never plant begonias directly into the soil, either in borders or in the garden, or anyplace where a cat or dog or a horse might be able to sample a bite of them.

We plant our begonias in hanging pots or in containers and planters that keep the plant above chest height, to make sure that curious cats and visiting puppies can’t reach them. Here’s one example of how we display begonias in our homestead, hanging from our porch rafters:

Begonias - bright and beautiful but can be irritating.
Begonias bright and beautiful in the early spring sunshine.

And although they are amazing at brightening up a stable, if you have horses make sure that you don’t put begonias anyplace where a curious horse could sample a nibble of them.