What is this plant?

I am located in Yellowknife, Northwest Territories, Canada. I found this growing in my garden. I don't recognise it as a wild plant indigenous to the area. And it doesn't look like the ones I planted. Maybe it came from the commercial gardening soil? The bracts are hard and spiny, hence wearing the gloves to handle them. You can see the flowers are tiny, only a few millimetres across. The plants are about 2ft tall.