"Puzzle 16 requires four steps completed in healing the tree, and three rolls of cloth. When it says "the Tree of Life is recovering" in your tech menu, you will start seeing a purple hummingbird flying around your village. At this point you can drag a villager onto the crates with the moth-eaten braids in the bottom left corner of the lab. They will take one of the braids and take it to a flat rock by the sea. Drop a villager onto the braid, and they will gather a roll of cloth to repair the rope. When you drop a villager on the finished rope, it will tell you that "the lei needs more flowers". Now watch where the hummingbird is goes. The hummingbird will hover around some flowers to pollinate them, after which you can drop a villager on the flower to pick it. If the hummingbird didn't pollinate a flower it will keep telling you "this flower is not in full bloom yet". You can usually get several flowers from one plant. You need six flowers for one lei and three leis to complete the puzzle. Note that if you interrupt your villager as they are carrying the lei to the tree you will have to make the whole lei again from scratch!"

Taken from Virtual Villagers 4: The Tree of Life Walkthrough & Cheats