The delphinium plant blooms in early June and requires pruning to promote a second flowering as well as more blooms.
Removing Faded Blooms
Removing faded blooms from a delphinium not only cleans up its appearance but also interrupts the reproductive cycle of the plant. The fading of a flower is the climax of a plant's growth cycle when seeds are released to propagate the plant. If this process is interrupted, the plant begins its cycle again, thus encouraging repeat blooms. Remove spent blooms by pinching flower tips and gently pulling until released. Cut with pruning shears if they do not come away easily.
Cutting old stalks back will give the delphinium renewed vigor and encourage a second flowering later in the summer. The remaining stalks must be removed at the crowns when the plants foliage begins to turn yellow. Ideally, for the delphinium to reach its full potential, only one flower spike should be allowed to develop in the first year, three in the second year and five in the third year. The delphinium is one of the few plants that will flower to “exhaustion” and this sequence will allow the plant attain its best.
To weather the winter safely and to ensure a full bloom for the following year, the delphinium must be cut back hard. Stems should be pruned to within 1 or 2 inches of the ground.