Gauge for summer

Canadian Fireweed grows in abundance more north, in Alaska and Finland and I suppose in Canada, judging by its name. Our son once told me that people in Alaska measure the progress of summer by the fireweeds. The flowers open up from the bottom up, when the top ones are done blooming, then summer is over.
This particular plant has faithfully popped up by the front porch all the years we've lived here. I credit God for it; it reminds me of my homeland.