Do you put wedding attire on invitations

Barn + rustic = does not equal formal attire. Based on your wedding location and theme, it would be completely understandable for your guests to assume that they don't need to dress formally.

Since formal attire seems to be important to you, I guess you have to tell people how to dress to your standards ("no Wal-Mart and no jeans!"). But I think you should still be prepared for guests to arrive dressed in a range of styles. It will be OK and will not ruin your wedding unless you let it.

I personally didn't put any of that on the invitations, because I wanted to keep it as short and sweet as possible, but if you feel like you should, then go ahead. You don't want to make the invitations messy and confusing though, so you should pick a simple design. We wanted to keep ours formal and elegant, so we used Magnet Street because they have all different styles/types of invitations which are all customizable: https://www.magnetstreet.com/wedding-invitations