Getting “Back on Track” with Common Milkweed

Sophie Breitbart, PhD student at University of Toronto Mississauga, tells us about her experience in the field working on milkweed.

I’m sitting in the railway station

Got a ticket to my destination…

-Simon and Garfunkel, “Homeward Bound”

Who would’ve thought that a young Paul Simon could have so much in common with a perennial herb with velvety undersides?

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Samreen Munim collecting floral trait observations.

A critical distinction between Simon and common milkweed is that the latter is homeward bound of it’s journeying towards the railroad. This was clear from the patch upon patch of rail-side milkweed, Aslepias syriaca, sighted around Southern Ontario this summer by my trusty team of field collectors (Lindsay Miles, Samreen Munim, and myself). Our goal was to find 100 populations of common milkweed, the main host of the Monarch butterfly, inhabiting the Greater Toronto Area before the summer’s end.

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Dr. Miles surveying milkweed near a right-of-way in suburban Toronto.

In the coming months we’ll use these populations’ plants to take us one step closer to understanding if and how common milkweed is adapting to city life. We wanted to implement a sampling strategy as heterogeneous as the territory by investigating a wide variety of places where the plant could be found. We’d crane our necks when driving past overgrown parkette gardens, unkempt roadside ditches, and residential neighborhoods. Thriving populations called out from rights-of-way, demonstrating their ability to regenerate after regular mowings. Green spaces were hit or miss, but twice yielded urban farms sporting the distinctive opposite leaves and pale pink flowers of common milkweed. Our constant vigilance amounted to a type of radar that proved impossible to turn off, even now during the off-season.

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Milkweed in bloom along the perimeter of an urban farm in Toronto.

Overall, the strategy worked. We’d often spend only a few minutes surveying a neighborhood in the Evo Eco Lab car before one of us found a pod-laden patch and exclaimed, “THERE!”. The fast-paced hunt for a parking spot began.

Unfortunately, sometimes our milkweed radar went haywire and before we knew it, sixty minutes had passed without a single sighting. We’d pull over and pore over our maps until we had a plan. Parks, like residential neighborhoods, could be promising but sometimes proved fickle. Highway buffers would have been fantastic if not for the fences that often blocked our entry. However, we did always have one trick up our collective sleeve: finding train tracks in our survey area. We’d put the car in drive and exhale sighs of relief, confident that common milkweed was awaiting us. In fact, we had a success rate close to 100% with this method.

After we arrived, the railway sites consistently triggered three specific thoughts:

  1. “More stressed plants.” Plants with wrinkly, tough leaves made regular appearances alongside the steep, gravelly slopes bolstering the railways. We speculated that the thick cuticles could indicate stress in the form of decreased water intake or desiccation caused by the frequent rushes of air that accompanied a passing train. (Have any ideas? I’d love to hear about it in the commends below!)
  2. “What is the relationship between railroads and common milkweed? Common milkweed relies on its fluffy pappus (the white, flossy silk attached to its seeds) to catch the wind and carry its kin to a suitable location. Does this plant have a soft spot for train tracks because it’s a convenient way to ensure a strong breeze when it comes time to scatter their progeny? What are the trade-offs involved in rooting near railroad tracks, such as physiological stress?
  3. “Time is of the essence.” It is imperative to be vigilant of an incoming train when you are doing field work near the tracks! We put in extra effort to complete our tasks and leave if we were sampling near an active railway.
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Usually railside milkweed was much easier to find than this fellow. Can you find it?

Notes taken and coordinates recorded, we again set off to find where the wind had carried the seeds of yesteryear.

 


About the author

Sophie Breitbart is a PhD student at University of Toronto Mississauga studying how urbanization affects gene flow in common milkweed (Asclepias syriaca), the host plant of the Monarch butterfly (Danaus plexippus). Her research aims to inform the construction of sustainable cities that also function as resilient ecosystems for flora and fauna.

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