I'd like to build an outdoor pen from my Hermann's hatchling but the sunniest and most secure spot is in the middle of a rhubarb patch. Will he eat rhubarb and is it safe?
Rhubarb leaves are toxic, the stalk is edible. Most (if not all) plants contain various levels of oxalic acid. Many of the foods that are commonly recommended as "tortoise safe" on this site and others actually contain what is considered to be high levels of oxalic acid including (but not limited to): Pumpkin, yellow squash, green peppers, various greens (collard, mustard, etc), escarole, dandelion and more! Oxalic acid in large volumes can have some negative health effects associated with it relating to human consumption, based on studies done. No one really knows for sure what, if any effect oxalic acid has on tortoises. May people are presuming that it has effects on tortoises equal to that of humans. I personally have never seen any confirmed study done on the subject with tortoises. I can tell you that I have been feeding the above listed foods, along with many others to my tortoises, including Hermann's, for as long as I've had them, many over 20+ years now. I have yet to see any problem that I can attribute to their diet content. I am a firm believer in feeding them a vast variety and good quality of foods of all types.
Admittedly, I have never tried to feed mine rhubarb. Probably because it just doesn't grow that well here where I live and isn't plentiful. I've tried eggplant on several occasions. None of my tortoises have ever shown any interest in it.