Every garden needs a planning center: a place where notes are kept, schedules are posted.
We built our greenhouse on the south end of our garage, and there was already a window there. So we have a window - which we never open - between the garage and the "toolroom" portion of the greenhouse. (A lovely view, though! NOT!)
But the window makes a fine whiteboard. And we've posted the "When to Plant What" information. We've also got post-it notes and some pens.