In my garden I have several of the plants shown below. At first I thought it is a weed, but then it was quite robust against cold weather and continued to grow slowly:
The leaves are long and sharp, the example shown below is about 30cm high and the leaves are 8-12cm long. I haven't seen a flower or anything for 8 months and the temperature has varied from -3 to 35 C over this period (including rainy and dry times) and the plant hasn't died yet.
Click to enlarge