It is not necessary to remove the mulch before fertilizing. Deadheading After perennials have bloomed, spent flowers and seed pods should be removed. Keep in mind that some perennials do not require deadheading since the seed pods are either not very visible or are quite attractive. Cut the flower stem down to a healthy leaf or side branch. This will keep the plants looking neater and will prevent them from wasting energy by producing seeds.
Some plants produce so many seeds and volunteer plants that they become overcrowded and invasive.
Deadheading will reduce the problem. Some perennials will rebloom if cut back after the first flush of flowers. Pinching Some plants will grow thicker and fuller if the terminal growth is pinched. This reduces the height and reduces the likelihood that the plant will be blown over by wind and rain or from the weight of large, heavy flowers. The result is a more compact plant with more but sometimes smaller flowers.