The long flower spikes of the gladiolus plant produce a multitude of blooms throughout their life. Each spike features many buds that eventually open and bloom. The buds don't always open all at once, so old flowers become unattractive as they wilt, detracting from the beauty of the remaining blossoms. The flowers near the bottom of each spike open first, and the remaining buds open in succession up the length of the spike. Removing the old flowers prevents the gladiolus from setting seed, allowing the energy usually spent on seed production to instead feed the bulb for next year's flower display.
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.