Re: Dowel Rod ----> Jo?
I'm no expert about wood etc, but here's a thought.
A karate group also uses the dojo I train in. They do some kind of work with a bo, and have half a dozen or so bo stored at the dojo. Only one of these is a genuine oak bo, the rest are all hardware store bought softwood.
As other posters here have already said, if you do any kind of contact, you want real oak or other hardwood jo. If it is a temporary measure for teaching basic suburi etc, softwood may be the way to go for a dojo "pool", while encouraging people to purchase their own proper jo.
All of our dojo have a pool of cheaper red oak jo and bokuto, but folks are encouraged to buy their own weapons, and can do so through the dojo (nice white oak weapons).