I've always wanted to try acorn flour. Acorns can't be eaten straight from the tree, so people developed ways of soaking them and treating them to get the tannins out so that they become edible.
I believe they were a staple part of the diet for many American Indians, so that might have played a part in the decision to make the oak the State Tree of Iowa.
I would be surprised if more states didn't also pick the oak, as it is the National Tree of the USA in general.
But then it's the national tree of quite a few countries apparently, including England and quite a few other places in Europe.
It's a bit ironic really to pick as your symbol a tree that attracts lightning strikes!