Who Steals Flowers?

Who would steal flowers? This is a question that's bothered me for awhile.
Several years ago the neighbours two doors down had their front yard landscaped. The next day, two large hydrangeas were missing. They had been dug up and stolen.
I still can't quite fathom it. How much could flowers possibly fetch on the open market? Or who would want plants that badly for their own garden that they'd be willing to steal them?
Then I saw a column in The Star, Who is stealing the flowers of Toronto?, that asks the same question.
The column poses questions, but has no concrete answers.
Additional things happen that shock me, of course. I can't put anything on my porch because it disappears. And I mean anything.
Plus a few years ago, during the night, what I only can presume was a drunken idiot snapped my fledgling, city-planted, lacy-leafed front garden tree in half.
But, for some reason, I can understand stealing furniture or drunken idiocy much more easily than stealing greenery, whose value is more about creating beauty and sharing it with your city than anything concrete.
The sign that a woman mentioned in the column put in her garden sums it up: "Stealing plants is a low and selfish act. What’s next? Punching kittens? You suck.”
What's your theory? Who is stripping Toronto's greenery, one plant at a time?
Vanessa