I'm stumped!
The only thing it really reminds me of is lettuce seedlings, there are a large number of different varieties of lettuce some of which have serrate or wavy edging. It doesn't quite look like lettuce but could it be something similar?
At this time of year you would expect a pot full of seedlings which can be planted out in the autumn to overwinter. The plants look like several small plants rather than one.
Does it have a distinctive smell at all when a leaf is rubbed?
http://www.hartnursery.co.za/i...
The leaves appear to be almost serrate, but not quite. I cropped off a part of the photo and enlarged it. There are some lettuce which have very crispy edges, the first leaves might look like these plants. It's an odd time of year for young lettuce plants unless they will be grown on in a greenhouse, there are winter varieties for such growing.
https://www.google.co.uk/searc...
The only other thing which comes to mind is Lobelia, they die back and make new growth which has this sort of habit.
http://www.chicagobotanic.org/...
