Grasp a spent flower between your thumb and forefinger. Hold the flower stem beneath the spent flower in your other hand to help support it.
Pinch off the old flower. Remove the entire flowering structure, including the swollen portion at the base that connects to the flower spike.
Remove each flower as it finishes blooming and begins to wilt. Check the spike every three to five days for wilted flowers and pinch them off as soon as you notice them.
Cut off the entire flower spike at its base with shears once all the buds along its length have finished blooming. Leave the foliage in place until it yellows and dies back in fall.