The Apiaceae or Carrot Family: The Good, the Bad, and the Dangerous

The Apiaceae or Carrot Family: The Good, the Bad, and the Dangerous
By Linda Dietrick, Master Gardener
Eastern black swallowtail nectaring on catmint flowers. Photo: Linda Dietrick

I hope that, for most of you, finding an Eastern black swallowtail caterpillar on your dill or parsley or carrot tops is cause for joy. Within a few weeks, those greenish-yellow caterpillars with the black and yellow stripes will crawl away, pupate, and emerge as one of our most spectacular butterflies. With their black wings spotted yellow, orange, and blue, and the tailed hindwings that give them their name, they are unmistakeable.

Like most butterflies, black swallowtails have specific larval food needs – in this case, plants in the family Apiaceae or, to use the older family name, Umbelliferae. The latter name comes from the fact that most members of the family have umbel-shaped inflorescences, with flower stalks of nearly equal length arising from a common center and forming what looks like a flat umbrella. Think dill flowers. Many kinds of insects feed on these flowers. The foliage, however, contains toxic compounds called furanocoumarins that black swallowtail caterpillars have uniquely evolved to tolerate.

Young black swallowtail caterpillar feeding on parsley. Photo: Linda Dietrick

A large number of vegetables and herbs belong to the Apiaceae family and are therefore potential black swallowtail hosts. Most butterfly books and websites only give a partial list, so here is the most comprehensive one I could assemble: angelica, anise, caraway, carrots, celery, garden chervil (Anthriscus cerefolium), cilantro, cumin, dill, fennel, lovage, parsley, parsnips, and sweet cicely (Myrrhis odorata).

 

 

Black swallowtail caterpillar on a dill plant. Photo: Linda Dietrick

If you grow any of these in your garden, you might have visitors. The butterflies lay tiny, pearly white eggs individually on the host plants. After four to ten days, the young larvae hatch, at first brownish-black with a white band, then becoming lime green and striped as they eat and grow. One caterpillar can clean the foliage off a single parsley or dill plant, so be generous and grow enough for yourself and your visitors.

Other than American angelica (Angelica atropurpurea), which is native to eastern North America, all of these umbelliferous herbs and food plants were introduced to this continent by European settlers. So, you might well wonder what the black swallowtail larvae were eating before that. There are in fact a number of plants indigenous to Manitoba that also belong to the Apiaceae. Not all of them are suitable for gardens because of their toxicity to humans, as I’ll explain. But these three are excellent garden candidates:

Heartleaf Alexanders (Zizia aptera)

Yellow umbels in June provide pollen and nectar for early pollinators. Reaching 30-60 cm in height, they prefer sun or part shade and tolerate dry soil.

Black swallowtail caterpillar on golden Alexanders. Photo: Linda Dietrick

Golden Alexanders (Zizia aurea)

With similar flowers, these are taller (60 cm) and prefer more moisture than heartleaf alexanders.

 

 

 

Aniseroot or long-styled sweet cicely in Assiniboine Park, Winnipeg Photo: Linda Dietrick

Anise root or long-styled sweet cicely (Osmorhiza longistylis)

Not to be confused with the non-native herb Myrrhis odorata, this is a woodland plant for a shady spot, about 60-90 cm. Dainty white umbels appear in June.

 

 

 

Common cow parsnip in Riding Mountain Park. Photo: hannerbanner via iNaturalist, CC BY-NC

In addition, you might consider growing common cow parsnip (Heracleum maximum syn. H. lanatum) as a statement plant reaching up to 2.5 or 3 metres. Lyndon Penner recommends it in his book Native Plants for the Short Season Yard on pages 99-100. It is a black swallowtail host and good for other pollinators. Lyndon doesn’t mention, however, that the furanocoumarins it contains can have an effect called phytophotodermatitis. If the sap gets on your skin and is then exposed to sunlight, it can produce serious burns, especially in sensitive individuals. As a matter of fact, the foliage of any of the Apiaceae, including food plants like carrots, can have this phototoxic effect, though apparently some are worse than others. As a precaution, wear gloves and sleeves when handling them, and wash clothing and skin after any exposure.

You may have heard of giant hogweed (Heracleum mantegazzianum), an invasive non-native plant from Eurasia that is downright dangerous for its phototoxicity. It has not yet been found in Manitoba, where it is listed as a Tier 1 noxious weed (eradicate without conditions), but it could survive our winters. It is already a problem in Ontario and British Columbia. Kristin Pingatore, Selkirk District Weed Supervisor, tells me she has been getting calls from people who have spotted common cow parsnip and worry that it’s giant hogweed. They both have white flowers, but the latter is much bigger – up to 5.5 m tall (see https://ckiss.ca/species/giant-hogweed/ for a photo).

Another non-native umbellifer that has become a weed is wild parsnip (Pastinaca sativa). It is actually the same species as the domestic parsnip grown in gardens, but it has escaped to the wild and become widespread. Reaching 1-2 m in height with yellow umbels, it is moderately phototoxic. In Manitoba, it’s a Tier 3 weed, which means it must be controlled if it is likely to impact the economy, the environment, or human well-being in the area where it is growing. You can report big infestations to your local Manitoba Agriculture office. If you go hiking, in the same way you would avoid poison ivy, stay away from plants with umbels.

Returning to your garden: one of the best known ornamental umbellifers is the annual Queen Anne’s lace (Daucus carota). Essentially, it is wild carrot, from which our domestic carrots are descended, but I don’t recommend planting it. Contrary to popular belief, it is not a native wildflower, but a Eurasian species that has become invasive in many parts of North America. Another annual that is sold as Queen Anne’s lace is Ammi majus, which has a popular red cultivar called ‘Dara’. It too is non-native, but so far, it has not proven invasive. However, it is phototoxic and poisonous to dogs, cats, and humans if ingested, so plant it at your own risk.

Finally, if you have ever battled that invasive plague bishop’s goutweed (Aegopodium podagraria), you will know from the flowers that it is in the carrot family. However, it is not a host for black swallowtail caterpillars, nor is it an exclusive host for any other insects. It is starting to invade woodlands and parks in Manitoba. Declared invasive in Ontario and an “alert” species in Alberta, its sale is banned in several northern U.S. states. It is on the list of Canada’s Unwanted Invasive Plants prepared by the Canadian Council on Invasive Species. Don’t plant it, and if you have it in your yard, please get rid of it.

Good alternatives to goutweed include Canada anemone (Anemone canadensis – native), wild ginger (Asarum canadense – native), fleeceflower (Persicaria affinis), and barren strawberry (Waldsteinia ternata). Or plant some nice parsley for yourself and the swallowtails.

References
Central Kootenay Invasive Species Society: “Giant Hogweed” brochure. https://ckiss.ca/species/giant-hogweed/
Canadian Council on Invasive Species: “Canada’s Unwanted Invasive Plants.” https://canadainvasives.ca/wp-content/uploads/2022/05/CCIS-Unwanted-Plant-List_Updated-May-2022.pdf
Lyndon Penner: Native Plants for the Short Season Yard. Brush Education, 2016.
“Phytophotodermatitis.” Wikipedia article. https://en.wikipedia.org/wiki/Phytophotodermatitis
Manitoba Agriculture: “Look But Don’t Touch: Poisonous Plants of the Carrot Family” brochure. https://www.gov.mb.ca/agriculture/crops/weeds/pubs/poisonous-plants-carrot-family.pdf
“Goutweed,” iNaturalist taxon guide. https://www.inaturalist.org/guide_taxa/670557