How to Cut Back Dianthus Flowers
- 1). Grasp individual stems between your thumb and forefinger, directly beneath the spent flower head. Pinch the stem to break off the old flower. Pinch of the spent flowers as they wither to prevent the dianthus from forming seeds.
- 2). Cut back all the flower stems once the main flush of blooms have faded. Trim the stems back to the foliage with pruning shears.
- 3). Prune back the foliage by up to a third of its height after trimming the flower stems. Make each cut immediately above a leave or bud on the stem. Lightly shape the dianthus when cutting back the foliage.
- 4). Trim back the stems and foliage a second time after the second flowering period completes. Dianthus may flower a third time in climates that remain warm into the early fall months.
Source...