Fetching details from the dictionary...
stalk; stem
「茎」 has another reading with different meanings.
core
このバラは茎くきが長くながくて花瓶かびんに飾りかざりやすいです。
The flower's stem is long and beautiful.
この植物しょくぶつは茎くきが太くふとくてとても丈夫じょうぶだ。
This plant has a thick, sturdy stem.