Butterfly host plants

Bees aren’t the only pollinators — butterflies and moths are as well.

I’ve seen at least a dozen different kinds of butterflies since I created my pollinator garden. Unfortunately, I only have pictures of a few. I’m still trying to remember to keep my phone with me at all times in the garden because you never know what’s going to stop by for a snack.

Monarch on Ontario blazing star
Monarch on ironweed.
They do seem to like purple flowers, don’t they?
This Wood Satyr (I think) narrowly missed being a Robin’s lunch.
A Giant Swallowtail butterfly has stopped by a few times, so I planted its host plant, Hop tree.
A Painted Lady butterfly and a few bumblebees enjoying nectar from Mexican tithonia. This large annual is a favourite nectar source in my garden. This video shows numerous Monarchs and Painted Ladies visiting during their fall 2017 migration.

I also saw butterflies that I never even knew about before; I saw a Spring Azure, a Mourning Cloak, Red Admirals, a Wood Satyr, a European Skipper, and even a Giant Swallowtail.

Nectar for adult butterflies

For butterflies, your pollinator garden must include both nectar for adults, and host plants for their caterpillars to eat. For years, I’ve had common milkweed in my garden for Monarch caterpillars, but I hardly ever saw any. I didn’t have flowers with nectar for the adults throughout the summer and into fall. Now that I have added many nectar plants, I see Monarchs almost daily.

Adult butterflies will drink nectar from the same plants as bees. To drink, they uncurl their long proboscis and use it like a straw. (They look like they’re using a paper party blower, minus the loud honking noise.) I’ve read that butterflies prefer visiting brightly coloured flowers for nectar, such as magenta, purple, red, orange, and yellow. Surprisingly, some types of butterflies avoid flowers and instead feed on sap, rotting fruit, mud, and even dung.

For night-flying moths, you can include common evening primrose with flowers that open late in the day and remain all night. Moths will drink nectar from the flowers, and they will in turn attract bats.

Host plants for butterfly caterpillars

Butterflies need to lay their eggs on specific host plants that their caterpillars can eat. Without host plants, you will not attract many butterflies or help them reproduce.

You probably know already that Monarch butterfly caterpillars can only eat milkweed. However, different butterflies require other, usually native, host plants. The Fletcher Wildlife Garden’s Gardening for butterflies page provides a good summary of the basics and a list of host plants for butterflies found in the Ottawa area. These are some host plants for butterflies in eastern Ontario that I’ve included in my garden:

  • American Painted Lady: pussytoes, pearly everlasting
  • Black Swallowtail: golden alexanders, as well as non-native dill, parsley, fennel
  • Eastern Tiger Swallowtail: wild cherry, wild plum
  • Mourning Cloak: pussy willow
  • Red Admiral, Question Mark: nettles
  • Fritillaries: violets
  • skippers: little bluestem and other native grasses
Can you spot the 2 Black Swallowtail butterfly caterpillars on our bronze fennel plant?

Identifying butterflies and host plants

The City of Toronto’s online PDF, Butterflies of Toronto, is informative and packed with photos of butterflies that are found in Ontario. I use the Butterflies and Moths of North America (BAMONA) web site to help with identification, and for information on host plants. I also like the Halton Butterfly Host Plant List because it is Ontario-based and provides listings by butterfly type as well as by host plant.

Native trees are super-host plants

Don’t overlook native trees and shrubs because they host hundreds of different moths and butterflies. In Bringing Nature Home, entomologist Douglas Tallamy includes tables listing native plants and the numbers of butterfly and moth larvae that they feed. (Here’s a version of Tallamy’s host plant table.) The numbers are astounding! Oaks support 534 different species, willow and cherry support 456 species each, birch supports 413. In this video from EcoBeneficial, Tallamy shows caterpillars on native trees in his yard, and discusses his book. Bringing Nature Home is available at the Ottawa Public Library (not the updated edition). There, you’ll also find The Living Landscape, in which Tallamy joins landscape designer Rick Darke to showcase attractive native plant gardens and the wildlife that inhabit them.

The Ottawa Trees in Trust program will plant a tree in your front yard on city property for free. They offer native and non-native options for large and small trees. Also, Ecology Ottawa offers free native tree seedlings at various events throughout the city each summer. In my pollinator garden, I wanted a native tree that would host caterpillars, and had high wildlife value, so I requested a Hackberry tree from Trees in Trust. It is the host plant for Mourning Cloak, Question Mark, American Snout, Tawny Emperor, and Hackberry Emperor butterflies, as well as some interesting moth species. The Natural Web has a great blog post called Hackberry, Butterflies and Birds.

Interestingly, many native plants do double- or triple-duty in the garden. For example, the Vaccinium family of shrubs, such as blueberry and cranberry, provide flowers for bumblebees, are the host plant for a whopping 288 species of moths and butterflies, grow berries for birds and bears, and rabbits eat the stems in winter. One nice side-effect of letting a native plant spread into a big patch is that it will provide food for everyone.

Host plants for specialist bees too

Did you know that there are even specialist bees that have host plants? Specialist native bees will only collect pollen from one kind of flower to provision their nests. Without that native plant, the bee will not reproduce. I have begun adding plants in my garden for specialist bees. For information on specialist bees and their host plants, see the EcoBeneficial post “Planting for Specialist Native Bees.”

Caterpillar mortality, or being near the bottom of the food chain

Butterfly and moth caterpillars are actually important food for baby birds and other wildlife. Each female butterfly lays hundreds of eggs. Only a small percentage (under 10%) of the eggs will actually survive to become adult butterflies. If you do find eggs, caterpillars or a chrysalis, don’t become too discouraged if they don’t make it. They’ve fed other wildlife.

Take care when raising butterfly caterpillars indoors

Some people actually bring butterfly caterpillars indoors to raise them so they have a better chance of surviving. This practice is popular, but controversial. Read this blog post, “Keep Monarchs Wild!” from the Xerces Society for more information. Raising a few butterflies in clean, uncrowded conditions can be both educational and harmless. If you choose to try raising Monarchs indoors, Monarch Watch provides detailed instructions.

Beetles, flies, wasps, and more

I own Heather Holm’s first book, Pollinators of Native Plants. In it, she covers a broader range of pollinators than in her second book, including wasps, beetles, flies, and hummingbirds. It is a treasure trove of interesting information and amazing pictures. I enjoyed this interview with Holm by Margaret Roach of the A Way to Garden podcast.

In 2018, I attended an enlightening public lecture by Jeff Skevington, an Ottawa researcher who studies flies. I was particularly interested to discover that they are also pollinators. Now that I have learned how to distinguish flies from bees, I can spot them in my garden all the time. There’s an interview with Dr. Skevington about declining insect populations in the Ottawa Citizen. I’m looking forward to his upcoming Field Guide to the Flower Flies of Northeastern North America (available at Amazon.ca).

For more information about lesser-known pollinators, visit this USDA Forestry Service page on Animal Pollination.