I used fresh water and put the yellow flowers in (and I have 32 villagers) but it just says 'An unfinished stew is cooking'. Am I missing something, or do I need to wait?

Have you put food in your stew?

1. Make a stew containing three yellow herbs and one bowl of food from the food bin (use fresh water)

2. Place 20 villagers on the stew. They will take the stews to the tree and sit down and honor it.

Note: You must have level 2 Dendrology to complete this event.

Requirements: Puzzle #1, #3, #7, #8, Level 3 Dendrology
Action: With extra cloth made, drop villager on sick tree limb. He will go get the cloth and return to bind the tree limb. Then drop him on the cutting tools and he will cut off the branch. Make a stew with 3 yellow herbs and fresh water. Drop all villagers, even children and nursing mothers, on the pot. They will carry a plate to the tree.
Description: "Your villagers have honored the tree."

Complete Puzzles 1, 3, 7, and 8. Attain Level 3 Dendrology. Make a stew with fresh water, 3 yellow flowers, and 1 bowl of food. Place at least 20 villagers at the pot. They will take the bowl to the tree and then contemlate.

Actually, they are 'honoring the tree', not contemplating. All I can think of is that you haven't used enough villagers. How many do you have (not counting babies)?

babes in arms don't count.

don't count the babies.