This summer in Ottawa, I saw more Monarch butterflies in my garden than ever before. According to social media posts and news stories, it’s been a great year for the eastern Monarch population (A flicker of hope in the insect world: firefly, Monarch butterfly numbers up).
Common milkweed patch
Throughout July and August, we saw Monarchs daily. They visited the flowers to drink nectar and females laid eggs underneath milkweed leaves. Monarch caterpillars can only eat milkweed.
Common milkweed roots run vigorously, popping up near and far. Since the roots aren’t dense, and don’t choke out surrounding plants, I just let it be. I simply pull out stems where I don’t want it. If running roots will bother you, plant with another variety of milkweed instead.
As summer progressed, the Common milkweed leaves became tough with age, and wilted and dried with the intense heat and scant rain. Recent research shows that cutting down parts of Common milkweed stands in mid-July helps Monarchs by encouraging those plants to sprout new, tender leaves for the caterpillars (Strategic Mowing of Milkweed Can Help Monarch Butterflies, Say U of G Researchers). This strategy may also help control aphids temporarily.
The more Swamp milkweed the better
As the Common milkweed waned, Swamp milkweed became the centre of Monarch attention. Despite its’ name, Swamp milkweed doesn’t require soggy soil; it actually seems fairly drought-tolerant once it has established. Its’ roots don’t run, either, so it stays in tidy clumps. The leaves are narrow, thin, and easy for caterpillars to eat. For a small urban garden, Swamp milkweed is a good choice.
Two years ago, I grew a white-flowering cultivar of Swamp milkweed from seed, and bought some regular pink-flowering plants as well. Both have self-seeded, so I have many small plants around the yard. I’m leaving them all because is such a great plant, attracting many insects that feed on the leaves, seeds, and flowers.
While watching female Monarchs flying around the garden, they seem to have trouble finding the milkweed. Next year, I am going to group some plants, and let others remain scattered, to see which arrangement is easier for them to find. I felt frustrated watching females circling around, searching unsuccessfully.
I do also have orange-flowering Butterfly milkweed. I grow it because it is short in stature and has such vibrant flowers. I don’t find that many Monarchs, or any other insects, visit these plants though. I am also experimenting with Poke milkweed, which grows in forest clearings and edges, so it tolerates more shade.
Nectar plants too
For a decade, there was little activity at the Common milkweed patch in the corner of our front yard. Once I added nectar plants nearby, we began to see butterflies. The Xerces Society has useful table, Monarch Nectar Plant Guide: Great Lakes, that I used to help with plant choices. Most often, I see Monarchs feeding on Anise Hyssop, Liatris, Echinacea, Ironweed, and Cup Plant. I want to grow more Liatris, and different kinds, especially after reading that it is a Monarch magnet (Liatris Ligulistylis: Meadow Blazingstar for Monarch Butterflies). I also grow non-native, annual nectar plants that are popular with butterflies, such as Mexican Tithonia, Brazilian Verbena, and Zinnias.
For the first time, since we had so many Monarchs around, we observed them mating. They don’t have elaborate courtship behaviours. A male Monarch would hang around the milkweed, perched on top of a tall plant waiting for females. Once a female caught his eye, he would pursue. After a lot of chasing every-which-way, if he was lucky, he would attach to the female in mid-air. Then she carried him around, seemingly unconcerned, and eventually landed on a tree branch or leaf, tired of carrying the extra weight. Apparently, they remain together for hours.
We also witnessed a dramatic love triangle with one successful suitor, and another hopeful male hanging on too.
Raising a few Monarchs
Despite all the Monarch egg-laying, we didn’t find any caterpillars — at all. Less than 12% of Monarch caterpillars make it to the 5th instar. Our dismal 0% survival rate, was very discouraging. Monarch eggs and caterpillars suffer from a variety of predators and parasites, such as ants, lacewing larvae, parasitoid flies and wasps, spiders, and so on. (Michelle D. Prysby, “Natural Enemies and Survival of Monarch Eggs and Larvae” in Monarch Butterfly: Biology and Conservation at Ottawa Public Library)
My youngest son and I decided to collect a few leaves with eggs on them to raise inside. (It is better to collect eggs, rather than caterpillars, because caterpillars harbour fewer diseases or parasitoid insects that can spread.) We cut the leaves off and wrapped the ends in wet paper towel. I placed each one in its own plastic container with a lid. Each day, I checked them. Once they hatched, I gave the caterpillars a new leaf daily, and shook their frass (poop) out of the containers. This was a lot of work. I can’t imagine raising dozens of caterpillars as some other people do.
After reading about a controversial study, Monarch butterflies raised in captivity don’t migrate, I ordered a mesh butterfly enclosure and put the caterpillars outside. For one last egg, I dug out the whole Swamp milkweed plant it was on, and put it in the enclosure. This was much easier than replacing leaves every day. If I ever raise caterpillars again, I am only using whole plants in pots, or I’ll cover plants that remain in the ground.
It was fascinating to watch each Monarch caterpillar grow so quickly, transform into a chrysalis, and then emerge as a butterfly. I had never witnessed this month-long process before. I’m glad we were able to help a few Monarchs survive to the adult stage. For more information, visit the Montreal Insectarium’s Mission Monarch Life cycle page.
Monarch migration underway
As early as mid-August, the first Monarchs began heading south. When our last delicate butterfly breaks out of its chrysalis, it will join them on this phenomenal journey. It is the great-great-great-great grandchild of Monarchs that spent last winter in Mexico.
In Ottawa, I see many Monarchs flying South-west along their migration route (red arrows on this Xerces Society map). I’ve also been following their movement throughout Ontario via Facebook groups: Pelee Paradise Sanctuary Monarch Waystation #10275, and Monarchs Migrating Through Ontario. Participants share spectacular photos of Monarchs congregating, feeding in gardens, and roosting in trees. They gather waiting for the wind to carry them southward across Lake Ontario and Lake Erie. Over the past few weeks, the numbers of Monarchs have increasing from tens, to hundred, to thousands. To follow Monarch migration beyond Ontario, you can visit Journey North.
(Interestingly, large numbers of dragonflies are also being seen migrating through Point Pelee National Park as well. I only recently learned that dragonflies migrate.)