This Mile High Gardening Conference, which took place in Denver over the weekend, had sessions aplenty about 21st Century growing techniques, with a big focus on aquaponics and a vertical garden installed by the Spanish firm Urbanarbolismo.

What wasn’t on the program? Marijuana — although it was originally supposed to be. The change in plans frustrated representatives of one dispensary, but the organizer says he had to cut it because of resistance from other sponsors.