To provide a fastening device for a plant capable of fixing and holding stems of a plant upward so that the plant will not have a wicked shape, and capable of cutting runners and the like without specially needing clippers or the like.

The fastening device for a plant comprises holding members 11, 21. Their front sides construct holding parts 12, 22 and rear sides construct operation parts 13, 23. They are swingable with a point placed inside the border between the holding parts 12, 22 and the operation parts 13, 23 as the fulcrum. The holding parts 12, 22 are energized with an energizing spring 41 so that the holding parts close. In the fastening device for a plant, a downward directed insertion pin 15 is placed on the holding member 11, the blades 16, 26 are formed on the operation parts 13, 23 so that the blades 16, 26 cut a runner by closing, and a stopper 27 extending toward the operation part 13 is placed at such an upper sided position of the operation part 23 that the stopper does not hit the operation part 13 even by closing the operation pats 13, 23.