How do you kill the roots of a conifer after cutting it down?

To kill the roots of a conifer after cutting it down, you can apply a systemic herbicide containing glyphosate directly to the freshly cut stump. This allows the herbicide to be absorbed by the roots, effectively killing them. Alternatively, you can use a mixture of salt and water or vinegar poured into the cut surface, though this may take longer and could affect the surrounding soil. Additionally, covering the stump with a plastic tarp can help to prevent regrowth by blocking sunlight.