It's possible to plant seeds (both normal and druid) in locations where it's physically impossible to reach, destroy or harvest the plants. If the power could only be used where you are standing, these accidents and exploits would be preventable.
It's not possible. It was, but is no longer and likely hasn't been for some time. All such seeds are self-only and plant at the PC's feet.
Well, for druidic seeds specifically, which seems to have been the vast majority of annoyances.
Ah, well you can plant normal seeds like this, which is why they can end up inside walls and bushes.
You can't sow normal plants (which are harmless and bear fruit) outside of a specifically designated gardening zone.
Consequently, you are better served bug reporting the specific gardening zone that allows the creation of inaccessible harvest plants.
You can plant them inside the gardening zone, in such a way they are inside one of the objects within the gardening zone.
For example the whole Secret Garden is a gardening zone. You can plant the seeds inside one of the walls.