The Leshy Warden and Treesinger archetypes allow you to have a leshy or plant familiar respectively.
I don't think that the bogun was ever made Open Game Content, so you won't ever see that exact creature in Pathfinder. However, the leshies from Bestiary 3 fill almost exactly the same role (small magically cultivated plant ally), with a lot more flavor and variety.
The Leshy Warden archetype that Dasrak linked to gives a druid a leshy familiar, which improves as its master advances in level.
The Tree Singer druid gains the option of a plant companion instead of an animal companion. However, leshies are not on the list of available companions. (See Advanced Race Guide and Ultimate Wilderness for the existing options.)
Leshies seem perfect. You can grow them, one's a PC race and there are familiar and archetypes using them.
Not sure if you're looking for a PC option, a pet or just a setting information so...
It's been too long for me to remember Boguns, but other than leshies, Ghorans fit. Humanoid-ish plant creatures, created by a powerful druid to help in a war that ended long ago.
On a "more construct - less plant" approach, Wyrwood are intelligent constructs made of, well, wood.
Created to fight and die in their wizard masters' private wars, until they decided this was in fact not a good deal, and liberated themselves.
The various ways to get plant companions open options like a young treant, what is basically a Piranha Plant, an actual puffball or other planty things.
Summoner also has ways to get plant eidolons, leshy or not.