Baby Groot's head has been hollowed out so he can be used as a planter for Tillandsia sp. "air plants". Air plants are widely available at retail and via the internet. They're very hardy and fairly low-maintenance, and as their name suggests, they need no soil.
Thanks to the original artist Byambaa for sharing this wonderful sculpt.
Shown here printed in colorFabb WoodFill
Yes, it could use some post-printing work, maybe I will find time...