When I first saw this duo I thought it referred to marriage, since weddings and partnerships seem to feature prominently in this duo, and it may very well be that this is what it means, but upon further reflection this made me think of my pregnant sister who is having an outdoor baby shower at the end of this month. This still seems to fall under the public couple thing. If you add to that the meaning that, by their own definition, this is something of a belated wedding celebration of their marriage which was done via courthouse, then I think it makes perfect sense!
Ring + garden (20): public agreement, marriage, public couple (e.g., high society, famous)
Garden + ring (25): engagement, public agreement, wedding