Unidentifiable Shrub

(Question)

I planted this shrub five years ago and it has never flowered. Any ideas what it is? It came from Vesey’s Nursery labelled as dwarf Joe Pye weed!

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(Answer)

Your mystery plant challenged a group of us!  Judging by the leaf arrangement, the prominent veins and the small toothed leaf margin, we believe it to be common buckthorn, also known as European buckthorn or Rhamnus cathartica.  One characteristic of this plant that may confirm our identification for you is that buckthorn is usually the first shrub to leaf out in the spring and the last to drop its leaves late in the fall.

What may have occurred is that the dwarf Joe Pye Weed that you purchased and planted in this location died over the winter. In its place the common buckthorn took over. This is an invasive shrub which is seeded by birds, very common in Toronto and sometimes hard to eradicate. With common buckthorn you usually do not see flowers and the fruit for many years, but in the meantime the roots get really well established.
According to Ontario’s Invading Species Awareness Program, this small shrub or tree is native to Eurasia and was originally introduced to North America in the 1880s as an ornamental shrub that was widely planted for fencerows and windbreaks in agricultural fields.  It has since invasively spread throughout southern Ontario as well as other provinces.
Fortunately for you, your buckthorn has yet to go to seed. I would suggest that you dig it out, perhaps after a good rain or soaking it with hose to loosen the roots.  Your original choice of Dwarf Joe Pye Weed (Eupatorium) is native to North America and would be a lovely addition to your home garden.

Sources:

www.invadingspecies.com/invaders/plants-terrestrial/common-buckthorn/

https://mnfi.anr.msu.edu/invasive-species/CommonBuckthornBCP.pdf

https://www.chicagobotanic.org/downloads/planteval_notes/no37_joepyeweed.pdf