The emotional rollercoaster of raising butterflies

Re: News journalist Baz Macdonald shares the emotional rollercoaster of raising butterflies from swan plants every summer.

Last summer I went into my local gardening store and asked a salesman where they kept their swan plants.

I remembered having a swan plant in my primary school and loving watching how the monarch butterflies that lived on it would transform from caterpillars to butterflies, and I was convinced it would be a lovely part of my summer gardening.

The gruff fortysomething-year-old man looked at me and said, "You better be ready to make some hard choices".

"What do you mean?" I asked.

Dead serious, he looked me in the eye and said, "They can’t all live, mate".

I shrugged off his comments and proudly took my swan plant home for what I thought would be a magical summer of watching caterpillars grow into butterflies.

I should have listened.

If you've never had a swan plant before, let me explain.

Swan plants are the host plant of the monarch butterfly. While monarch butterflies aren’t native to New Zealand, they are thought to have migrated here by themselves in the mid-1800s and have become part of Aotearoa's ecosystem.

Research has shown that internationally the population of the monarch has dropped by 99.9% since the 1980s because climate change is impacting the very particular species of milkweed, including the swan plant, that monarchs need to survive.

In New Zealand swan plants don’t naturally grow frequently enough to support the monarch population, and so there have been efforts over the past several decades to have gardeners grow them at home.

If you place a swan plant in your garden over the summer, it won't take long before you see monarchs landing on the plant to lay their eggs.

Five days later the eggs will begin to hatch into adorable little caterpillars.

This is where the trouble begins.

The problem is the number of caterpillars that will hatch on your plant.

Within days, there were dozens. Within a week, I had almost 50.

And those little caterpillars absolutely devour the leaves on your plant.

Doing the maths on how many caterpillars I had and how much food it would take for them to make it to chrysalis, I started to realise the wisdom of what that salesman said to me.

"You better be ready to make some hard decisions."

If all of these caterpillars remained on the plant, then all of them would starve, and none of them would become butterflies.

It was clear what needed to be done, but that didn’t make it any easier.

I picked off all but the largest caterpillars and placed them in the garden – hoping they would find a new home, but knowing they wouldn’t.

What makes it worse is that every day I would come back and more baby caterpillars would have hatched, so I had to do the whole cursed process over again.

In total I culled over 40 caterpillars and kept seven to try and grow to butterflies.

But even that was a challenge.

With the caterpillars having decimated my plant, there just wasn’t enough food left to get them all the way there.

I wasn’t the only one having these problems. A bunch of my friends said the caterpillars on their plants had already stripped the leaves bare and reached out to me asking if I had any leaves I could give them.

At this point in the summer, all of the swan plants were sold out in my local gardening stores and the range of plants monarch caterpillars can eat is very limited.

Googling around, I could only find mention of one alternative food – pumpkin.

But this is only an option for caterpillars right at the end of their growth. And sadly, as I was to discover, it is not a good alternative at all.

While large caterpillars will eat pumpkin, it can cause a deformity in the cocoon phase which means they will either fail to produce a proper chrysalis, or will produce butterflies with weak wings.

After having seen this first-hand with a few of my butterflies, I now know that the Moths and Butterflies of New Zealand Trust strongly recommend you not feed caterpillars pumpkin because we don’t know the impact these deformities might have on the overall butterfly population.

Ultimately, only four of my caterpillars successfully hatched into monarch butterflies. And getting to that point took way more attention and emotional energy than I had expected.

This summer, I kept my swan plant in the garden and largely ignored it.

Coming back from two weeks away over New Years, I found it stripped bare with just a few empty chrysalises hanging from its stalk.

While it can be an emotional rollercoaster, we actually need New Zealanders to grow swan plants.

The Jane Goodall Institute New Zealand encourages people to have swan plants in their gardens, as the plant is not common enough in the wild to support them.

However, the Moths and Butterflies of New Zealand Trust have warned that the pesticides on some store-bought swan plants may be killing monarchs – so they recommend you either grow them from seeds, or keep them indoors for a few months if they're bought full-grown before placing them outside.

If you do, I'll give you the same advice I was given – you better be ready to make some hard choices.