The Skyward Gardens in CityVille will be introduced by a new mission in the game, the Upward Growth quest which asks the following from you:
– Place and upgrade Skyway Gardens to Level 2
– Build 3 Skyway Gardens buildings
– Ask friends for 10 Flower Pots
Now, building the Skyway Gardens themselves is a real pain in the behind as you need to collect a lot of items and there are 6 building stages until you reach the 1 million coins reward mark. For the second stage you only need 9 items, but things get more and more difficult as you progress.
Fortunately, the only good thing that appears to be now is that there is no time limit for the Skyway Gardens in CityVille, so you can take your time and know that eventually you will get your items and bag in the reward.