tom thumb
noun

1. [usu. as modifier]a dwarf variety of a cultivated flower or vegetable
   矮生花卉，矮生蔬菜
   Tom Thumb lettuce.
   矮生莴苣。
   
2. a small wild flower, especially bird's-foot trefoil
   小野花（尤指牛角花）
   

语源

1. late 19th cent.: from the name of the hero of a children's story, a ploughman's son who was only as tall as his father's thumb