What mechanism does cultivation use to kill herbaceous perennials?

The correct answer highlights that cultivation kills herbaceous perennials primarily by destroying and cutting underground storage organs. Herbaceous perennials have structures such as tubers, rhizomes, or bulbs that store energy and nutrients, allowing the plant to regrow after certain periods. When cultivation occurs, these underground storage organs are disrupted, which prevents the plant from accessing its energy reserves necessary for growth and recovery. Without these organs functioning effectively, the herbaceous perennials can decline and eventually die.

Other mechanisms, such as removing nutrients or promoting competition, may influence plant health but are not the direct cause of killing these perennials. While promoting competing plants may help inhibit growth, it does not directly address the survival mechanisms of the perennials. Similarly, creating a dense cover can suppress some growth but does not specifically target or destroy the underground structures critical for herbaceous perennials' regeneration. Thus, the most effective and targeted mechanism is the physical destruction of their underground storage organs through cultivation.