Janet wrote:
I have heard (on here, I think) that the later in the season, the less
unpoisonous they become.

The later in the season, the higher the level of oxalic acid.
People with gout, rheumatoid arthritis or kidney stones may want to
avoid that.

http://oxalicacidinfo.com/

But. I'm curious if this is the case, because this isn't long-season
rhubarb, this is "grew in March, died off by May, decided to start growing
again in July". It's almost like it's gone into next year's growth early
due to the odd weather (which I wouldn't at all put past it, but it'll
probably be very tired by next year!)