Kawakawa's holey leaves
"If you're harvesting kawakawa, only pick the leaves with holes."
It's advice you'll hear from almost everyone. In fact, many people believe the holey leaves are the only ones worth harvesting for medicine.
But have you ever stopped to wonder... why?
Those familiar holes aren't caused by slugs or snails. They're made by the native kawakawa looper caterpillar, which feeds almost exclusively on kawakawa leaves.
For years, people assumed the caterpillars must be choosing the "best" leaves. It sounds logical... if the insects keep eating those leaves, surely they must be superior?
Researchers at Lincoln University decided to test that idea.
They lined up untouched leaves, leaves that had already been chewed by caterpillars, and even leaves with artificial holes punched into them. Then they watched to see which leaves the caterpillars would choose next.
The result surprised everyone.
The caterpillars showed no preference at all. They happily fed on leaves with holes, leaves without holes, and leaves with artificial damage. The researchers concluded there was no evidence that previously damaged leaves were less or more attractive to the caterpillars.
So does that mean the "only pick holey leaves" advice is a myth?
Not exactly.
More recent research has shown that when the kawakawa looper feeds, it triggers changes in the leaf's chemistry. Those chemical changes support what mātauranga Māori has recognised for generations, that caterpillar damaged leaves have different medicinal properties. Rather than the caterpillars selecting the best leaves, it's their feeding that helps create them.
One of my favorite teachings from my rongoā kaiako, Donna Kerridge, adds another beautiful layer to this. She taught that all of our tīpuna come from the forest, including the tiny kawakawa looper caterpillar. Before we harvest our rongoā, we first allow our little ancestor to feed. It's a reminder that we're not separate from nature, but part of it, and that harvesting begins with respect and reciprocity.
I love stories like this, where traditional knowledge and modern science don't compete, they complement one another, each helping us better understand the remarkable plants growing around us.
A little harvesting tip, too. When gathering kawakawa, avoid picking the tiny young leaves at the tips of the stems. Instead, look for the "grandparent" leaf, the oldest leaf furthest back along the stalk. You'll notice it has a flatter base where it joins the stem and it snaps off easily with a gentle twist. Leaving the younger leaves allows the plant to keep growing strong and healthy, ensuring there is plenty for future harvests.
p.s. I wrote an article about the Kawakawa flowers last week, you can read it here:
https://www.wildbotanica.co.nz/blogs/articles/kawakawa-flowers-aka-berries
Kawakawa is covered in my online foraging course:
https://www.wildbotanica.co.nz/collections/online-foraging-course
We always discuss Kawakawa in my in person foraging workshops, as it's so abundant around NZ, book a workshop here:
https://www.wildbotanica.co.nz/collections/foraging-workshops/products/wellington
I’ve also written 4 x foraging guides specifically for foraging in NZ.