This is part 35 of my 100% Super Mario 3D World Walkthrough. This part includes World Flower-1, World Flower-2, and World-Flower 3. See the description below for the times for each of the green stars in these stages.
00:05 World Flower-1 - Switch Shock Circuit
00:12 - Green Star #1
01:54 - Green Star #2
02:45 - Green Star #3
03:48 World Flower-3 - Piranha Creeper Creek after Dark
04:04 to 05:00 - Green Star #1
05:46 to 07:40 - Green Star #2
07:54 to 08:07 - Green Star #3
08:49 World Flower-2 - Floating Fuzzy Time Mine
09:07 - Green Star #1
09:35 - Green Star #2
10:17 - Green Star #3