I am located in Southern Ontario, Mississauga. I found this plant growing in a shady spot in a client garden. The soil is rich and there is a watering system in place, and the whole garden gets well watered. It was very sturdy and healthy looking. The leaves were quite attractive and neat, and until it flowered this week, producing many tiny pink flowers, I thought it might have been an actual desireable perennial planted previously by the owner Once it flowered, all semblences of "neat and tidy" were gone. The flowering stems shot about in all directions, and although pretty, this was clearly not a showy garden plant When I dug it up, the thick, sturdy roots went down beyond a foot and I was unable to get all of it out. I managed to get several shots of the plant in place, and later got my partner to use his closeup lens to get the flowers and partial root. We tried to photograph it from several angles and as close as possible. The flower size is roughly a 1/8 of an inch. the plant height before flowering was roughly 24". Once the flowers appeared it reached 36". None of my wildflower books had anything like it. A lot similar, but none exact.
Gypsophila paniculata?? I'm not entirely satisfied with this ID, as the flowers on it seem to be white, not pink. But Gypsophila paniculata in Flora of North America @ efloras.org says they can be " rarely light purplish pink". Gypsophila paniculata photos Saskatchewan Wildflowers (saskwildflower.ca) It's a known weed in Ontario: ard-weeds-babys-breath.pdf (alberta.ca)
Leaves look a little bit broad for Gypsophila paniculata, though I suppose there could be cultivars (or cultivars of similar species). Definitely in the Caryophyllaceae.
Thanks to both Wendy Cutler and Daniel Mosquin for your responses. It certainly does bear a strong resemblance to its domesticated relative, but without the charm (in my opinion). I suspect that this plant will probably reappear because I was unable to get all the root out. It was growing between some sprinkler lines and I really could not get in there effectively with a spade. Thanks again for your responses.
