Tinkster, my Pink Cups took over too, but I let them.
Sometimes you just have to step back and leave well enough alone.
I will never grow Silk Stockings with Baby Doll again though.
Silk Stockings almost choked my Baby Doll to death.
MCP, can you bring the container into a garage, or shelter of some kind?
Or start some in another pot, and do an experiment:
Sink one pot and bring another into an indoor cold shelter.
I am constantly pulling runners of my Pink Cups and literally dropping them into other aquatic pots for 'groundcover'.
Sue, where do you live where it is so dry?