Swan Plants & Toxicity

Asclepias Swan Plant
  • Botanical Name: Asclepias physocarpa/Gomphocarpus physocarpa

The Swan Plant is loved by many Kiwis, as it’s the host plant of the Monarch Caterpillar, which lives on the plant for approximately 2 weeks eating as many leaves as possible, before transforming into a beautiful Monarch Butterfly.

I have come across many ECE educators who assume swan plants are poisonous and not allowed in pre schools… but how poisonous are they really?? In fact a child has to eat 10% of their body weight in swan plant leaves to actually get sick. That’s quite a lot of leaves! An average 3 year old weighs 15 kg, so thats 1.5 kg’s worth of green leaves that they would have to eat. You are allowed swan plants in ECE places as long as procedures are in place if an incident happens and staff are all aware and knowledgeable beforehand. To put this into perspective, even the daffodil is hazardous as the bulb is poisonous, the seeds from the Kōwhai tree too – even carrot tops (but a child will have to eat a wheelbarrow full of carrot tops greens to become sick). We also have to remain cautious with the seed pods that grow on the plants at the end of the summer, these look like large spiky balls that produces milk sap if squashed. This is also harmful. Always let the seed pod dry out and become brownish before letting the child handle and look at. This is where the swan plant gets it name from too!

Seed Pod – resembles a swan

I know first hand that teachers don’t take their eyes off a pre schooler for even a minute. A child would have to eat for a few hours constantly to ingest enough swan plant leaves to become sick. There is not normally that many swan plants around in pots in classrooms for the child to eat , especially as the caterpillars eat the leaves so quickly, unless your ECE centre has an extremely large Swan Plant bush in the ground outside. From personal experience I even have trouble getting one spinach leaf or other green vegetables into my children let alone a swan plant leaf. I’ve educated my children from a very early age not to eat green strawberries or touch caterpillars etc like most parents. Every pre school I go to there’s an endless amount of activity going on and toys to play with. I’m sure children will not become bored or stupid enough to eat that many leaves. The slight risk of a child becoming sick outweighs the amazing wonderment and the expansive learning opportunities that the child is exposed to with the magical life cycle of a Monarch butterfly. Children learn from a real early age not to eat things out of the garden randomly as they follow our lead. It’s all about educating our young children about their natural environment and everyday plants and creatures, that belong on this earth too.

When I do my talks I teach about the importance of not touching the swan plant just in case the white milk sap of the plant then gets rubbed in your eyes accidentally. which can sting for a couple of weeks and is potentially dangerous. This applies to adults who are gardening in their own back yard Always wash your hands immediately after handling swan plants, as you might wipe your eyes to get your hard working sweat off or the sap could splatter from trimming the stalks.

I’ve seen so many great secure enclosures at pre schools where they have placed their plants. Below are some ideal places that can easily be replicated…(someones handy grandad, or wood work clubs could assemble and make up) The enclosures are also great for the little ones to see the caterpillars and still watch safely, and tempted little hands cannot squash the caterpillars or stop the Monarchs from laying eggs. This is a great bonus, so your plants can become mature and bushy and they can still spot the caterpillars and chrysalides.

Kids First New Brighton & Estuary Rd Pre School
Above is the swan plant enclosure at Kids First Papanui – Lids fold in completely to close

Plants and fungi make toxins to ward off bacteria, insects and animals that may eat them and to protect their area from competitors. The caterpillars are poisonous as this stops them being eaten by birds. This is just nature’s fascinating way.  There may be many poisonous plant in your garden so the list below is really good read. 


Thanks to Manaaki Whenua/Landcare Research which has published two free handouts with information on common plants. These can be accessed below: I will be printing these out and taking them along to my talks for people to read/copy.

https://www.landcareresearch.co.nz/publications/factsheets/poisonous-plants

And always keep the phone number 0800 POISON (0800 764 766) handy just in case you need it!

1 Comment

  1. Thankyou …so so so much for your wonderful insight …the common sense law for adults to find out …the facts .
    Our children need to look up around themselves ..what needs air ,awareness of their changing daily environment as do adults ..we are learning together ..never thought of caging the butterfly ,looks great ….I am fortunate to lease council land ,1/2 acre ..butterflies ,now wild cats raising kittens ,hens hatching chicks ..an amazing experience …our tiny steps working alongside Nature ,here in Methven …those ,yes ..you ..if passing thru METHVEN …PETER RABBIT ,OUR SCARECROW IS AT THE ENTRANCE ….THIS IS A KIDS WORKING GARDEN ..COME SEE WHAT THAT MEANS ,Sue and kids from Childcare@sues

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