The Wood Folk Diaries: Volume 3, Chapter 12: Black Swallowtails and Carrots

Dear Wood Folk,

For readers in Haliburton area, it’s not impossible we could see a black swallowtail (papilio polyxenes). Their range mostly stops in southern Ontario, but they are often seen in Peterborough. Because it’s such a longshot and I don’t spend much time to the south, I don’t have a picture of this butterfly. But you can check them out at Butterflies of Ontario. They’re similar looking to the swallowtails we covered earlier in the year, but black of course. Keep an eye out anyway, in open wetlands and roadsides full of the likes of Queen Anne’s lace and its many look-a-likes.

Black Swallowtail Plant Allies

The black swallowtail is mainly attracted to common rue (ruta graveolens) and carrot (apiaceae) family plants. The later of which we have a dozen species around Haliburton.

These carrots include native plants like golden (zizia aurea) and heart-leaved Alexander (zizia aptera), hairy sweet cicely (osmorhiza claytonii), bulblet-bearing water hemlock (cicuta bulbifera) and spotted water hemlock (cicuta maculata). These hemlocks (not to be confused with the tree) are some of our most poisonous plants. So if you want to plant something outside of the vegetable and herb garden to potentially attract a black swallowtail, sweet cicely and Alexanders are local go-tos.

Hairy sweet cicely (osmorhiza claytonii)
Hairy sweet cicely (osmorhiza claytonii)

When it comes to lists of what attracts this butterfly, it’s sad that the Alexanders and sweet cicely that are native here get overlooked for only garden herbs or worse, invasive plants like wild parsnip.

I understand native hemlocks being overlooked, and the nonnative poison hemlock (conium maculatum). Black swallowtail caterpillars are able to detoxify the furanocoumarin chemicals in these hemlocks, but it’s toxic and deadly to humans. Even weed-whacking hemlock once almost killed a man in the States.

You see some of the this butterfly’s invasive host plants getting blasted every year on social media for causing photosensitivity to sunlight, which can cause serious reactions, blisters and burns. The hogweeds and wild parsnips are a general tale of caution to not get any unknown plants sap, juice, etc., all over your skin. There are tons of plants that cause photosensitivity that are not demonized on social media. The carrot family seems to be taking all the heat. (FYI It can be hard to tell carrots apart. There’s a Facebook group called Know your carrots – Apiaceae Identification specifically for trying to ID tricky carrot family plants!)

Bulblet-bearing Water Hemlock (Cicuta bulbifera)
Bulblet-bearing water hemlock (cicuta bulbifera)

In lieu of the native hosts, leaving some wild carrot on the side of the road isn’t the worst idea. It tends to stay on the roadside rather than spread into wilder spaces like the more aggressive wild parsnip.

Vegetable and herb garden plants like caraway, carrot, celery, chives, dill, fennel, lavender, lemon balm, oregano, parsley, rosemary, sage, turnip, and more attract a variety of butterflies. The bolded ones are some of the black swallowtail’s favourites.

In their northern range these butterflies have two generations and overwinter instead of migrating. As adults these swallowtails love milkweeds, native thistle, native phlox and many of the other usual nectar all-stars.

Next month we’re getting Christmas-y with the silvery blue butterfly!

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