From this page:
https://garden.org/special/aco...
You get an acorn for each photo you post to each specific gallery of each plant.
So if you post 3 photos of a "Bloom" of a particular plant, you get one acorn.
But if you post 1 photo of a bloom, one photo of the leaves, one photo of the trunk, one photo of the seeds, you would get one acorn for each of them.
In this case, you posted three bloom photos of
Dragonfruit (Selenicereus monacanthus) and got one acorn for the first photo.