The second flag for map items
Looking at flowers, it seems the only use the second flag has is to be set when the flower has been watered (or rather, when the tile it sits on has been watered). Notably, there's no difference between the three different watering cans or even when it's been watered by a villager- all of these just result in the second flag being set to 40 (0100 0000). I've no idea how gold roses work with this.
At a glance the only other object I can find using the second flag is rocks- the breakable rock has 04 set, while some of the permanent rocks have 08 set with 00-03 set in the first flag- presumably coin rocks + which player character gets it.
- Also, fruit trees that've been shook recently, likely counting days until the fruit spawns again.
To research:
- Watering the tile a rock is on (probably just results in 48 or what have you in the second flag)
- Hack in some wilted black roses to water and see what marks them to turn gold