Deadheading is the removal of spent flowers before they go to seed. Some people refer to deadheading as pinching. The reason for doing it varies with the plant but, in any case, it conserves energy that the plant can direct elsewhere.
Removing spent flowers from most annuals will often result in a new flush of flowers. Keep doing it as long as the plants keep pushing new flowers and you may be able to enjoy blooms from the same plants all season long. Annuals live for only one season so the main reason for their being is to flower, drop seed to continue the species and then die. Deadheading may extend their life by encouraging them to reflower over and over until their flowers successfully go to seed.
Bulbs are different. Removing the flowers when they begin to wilt but before they go to seed won’t result in a new flush of flowers. They’re one and done for the year. However, they need energy to produce next year’s beautiful floral display. Removing spent flowers will let the plants direct food being made by the green leaves to the roots, rather than to the seed making process. That’s why it’s important to keep the leaves in place for as long as they’re green. The food being made through the process of photosynthesis will be stored in the roots (bulbs) until next spring when it will direct its energy to once again welcome spring with beautiful flowers.
When the leaves turn yellow or brown, that’s the time to remove them. It’s a good idea to identify where your bulbs are planted with tags stuck in the ground. The more information you can put on the tag the better. At least identify what the plant is and the color of the blooms. This will reduce the chance that you’ll inadvertently dig them up while working in the garden. It’ll also keep you from mistakenly mixing up colors if you plant more bulbs in the same bed this fall.
What about flowering shrubs? You can deadhead these, too, but don’t expect a second flush of flowers. Most shrubs only bloom once a year. A few, such as Buddleia (butterfly bush), have a long blooming period so they’re in flower continuously from spring to fall. Deadheading flowering shrubs will keep them looking tidy and encourage them to direct the energy that would be used in the seeding process to other life-enhancing purposes.
Some gardeners interpret the term “pinching” as the only way to remove spent flowers. However, some plants have very thick stems, making pinching difficult, resulting in a ragged stub. Using pruning shears, or even kitchen shears is perfectly acceptable. Scissors will give you a nice, clean cut rather than looking like a leftover from a critter’s dinner.