I accidentally pollarded the silverbeet in my raised, wicked bed out back this summer. We went away for a month over Christmas (I'd been neglecting the stuff for a good month before that, though) and it had to survive on nothing but rainwater and the residual water in the reservoir. Cue at least a week of 35C+ days just before we returned, and the stuff was awfully crispy. To my surprise, it managed to survive the baking and is now shooting all along the length of the stalk.
It's been in the ground and growing for a good 18+ months, so the root system must be pretty huge by now. The stem just keeps getting fatter and fatter and I keep chopping the flower stalks off when they come up. If I remember to grab the camera next time I go out there I'll take photos to post.
You've also just given me the idea to broadcast silverbeet seed around the yard and see if/where it comes up. The packet's pretty old and the yard's tiny, but I'm sure a bit of volunteer silverbeet would do everybody some good.