I consulted my new iBook’s dictionary (complete oxford) as to what an arboretum is. This is what I got:
arboretum |ˌärbəˈrētəm| noun ( pl. -retums or -reta |-ˈrētə|) a botanical garden devoted to trees.
Which is good to have cleared up amid ABC Online’s reportage of some very fancy footwork by Our Brave Leader on the subject of just how much it’s going to cost to build a second botanic garden in a city of 300,000.