mighty good stuff there. pick it when it is young and no purple what so ever, wash is then boil it in three changes of water, throw some bacon in for seasoning and then wonder what happened to it all when it boils down to a small bowl. You can eat the stalk when it is young and no purple showing.
When it matures. like you have there then it is quite poisonous.
The really young shoots are good with scrambled eggs as well. I stopped eating it very much when I found out that it has cancer causing properties.
However, if things got bad it would definitely get rotated into our diet. It does grow all over the place here in SW Missouri - very plentiful.
If you dig up the roots in the winter & move them inside you would get some small greens during the winter. I've tested this & it works. Not too hard to find in the winter because the previous years stalks are pretty tough & take awhile to break down all the way.