Gardens are in high season now and plant maintenance can be a daily chore to keep the gardens in prime condition. Deadheading is a big part of the work during this time of year. Removing old flowers improves the appearance of the garden and in some cases has the added benefit of keeping the plant in flower production.
Annuals such as zinnia, dahlia, and marigold and perennials such as echinacea, tall phlox, and shasta daisy respond well to deadheading. Cutting the flowers for arrangements will have the same result with the added benefit of enjoying the flowers indoors.
Removing old flowers helps to keep plants clean as well. I always try to cut hosta flowers before they get old and fall apart and litter the foliage below. Rose bushes require frequent pruning also. Deadheading here helps to keep the shrub in flower production and keeps the surrounding plants clean from drying petals.