Which tool should Hailey use to cut the stem after completing wiring and taping her flowers for a boutonniere?

In the context of floral arrangement, particularly for cutting stems after wiring and taping, using diagonals, or diagonal cutters, is the most appropriate choice. Diagonal cutters are designed to create a clean cut at an angle, which allows for better absorption of water when the flowers are placed in a vase or kept hydrated in their final arrangement. The angled cut increases the surface area of the stem that is in contact with the water, thereby enhancing the flower's longevity.

Furthermore, the use of diagonal cutters provides precision control, reducing the risk of crushing the stem. This is particularly important for delicate flowers used in a boutonniere, where maintaining the integrity of the stems is crucial for aesthetic purposes and the flowers’ health.

Other tools, such as scissors, while they may be usable, do not provide the same level of precision or the angled cut that is optimal for floral work. Cutters and snips, although effective for cutting through tougher stems, might not offer the finesse needed for more intricate arrangements like a boutonniere. Therefore, the precision and effectiveness of diagonal cutters make them the most suitable choice for this task.