Speaking of this pie, It's rhubarb. We have a massive rhubarb plant outside, that is pretty much eating our little garden space. I've taken a ton off of it three times already, and it's still up to my waist.
I don't know if you've ever had the stuff plain, but it's bitter nasty (side tip: the leaves are poisonous). I had little faith it would taste okay in anything...but I guess if you put just about anything in a pie it's going to taste good.
And it really is.