What method is generally needed to kill the growing points on established perennials?

To effectively kill the growing points on established perennials, using translocated herbicides in combination with mechanical methods is typically necessary. Translocated herbicides are designed to be absorbed by the plant and move through its system to target the growth points, which may be located underground or in difficult-to-reach areas. This ensures that the herbicide reaches and affects the entire plant, including the roots and rhizomes, where perennials often store energy and are capable of regrowth.

Mechanical methods, such as cutting or digging out the plant, can be effective in reducing the number of plants, but when used alone, they may not sufficiently kill the plant or eliminate all parts capable of re-sprouting. Therefore, combining these two methods enhances the likelihood of complete control over established perennials, as the mechanical action can help to disrupt the plant structure while the herbicide works to kill the remaining parts.

Contact herbicides, while useful, only affect the parts of the plant they come in direct contact with and often do not adequately penetrate to kill the entire plant, making them insufficient on their own for established perennials. Soil cultivation techniques may assist in controlling growth, but they also may not specifically target the growing points effectively without the aid of herbicides.