Leavanny is a thin, yellow, bipedal insectoid Pokémon. It has a broad, split leaf around its large, round head and it has long antennae that end in semicircles. Its eyes are red with no apparent sclerae. Its tiny thorax is dark green, and its long abdomen is yellow and covered in a green leaf. Its hands are long and leaf-like with a "bite" taken out of each. Its upper arms are also leaf-like, but with a vein of yellow at the top. Its thin legs are yellow with dark green, thick segments around its upper legs, making them appear armored.
Leavanny lives in forests. It is very parental and uses its cutters and a sticky silk it produces to create clothing made of leaves for small Pokémon. It also warms its eggs with fermenting fallen leaves.
Leavanny has the characteristics of several insects. Primarily, it appears to be based on a bipedal Phylliidae, but like its pre-evolved forms, it may also be based on the silver-spotted skipper and weaver ants or leafcutter ants. It also shares some characteristics with a praying mantis. Its leafy "dress", "collar", and "paned sleeve" arms may be based on fashion in the early 1600s. Because of the way it acts towards smaller Pokémon and its baby Sewaddle, it could also be based on a human mother. Its general body structure is also similar to that of a Choeradodismantis, which also have laterally expanded thoraxes and abdomens.
Leavanny is a combination of leaves and nanny. It may also derive from Levana, the ancient Roman goddess of newborn babies.
Hahakomori may be a combination of 葉 ha (leaf), 母 haha (mother), and 子守 komori (babysitting).