Make a simple cut just above a set of leaves or the next stem below a bloom to deadhead -- remove an old, faded flower from -- the annual or common sunflower (Helianthus annuus). You might enjoy the bright appearance of your sunflower plants as they are, but deadheading them may help you enjoy their future blooms even longer.
Why to Deadhead
A simple reason exists to deadhead sunflowers -- and lots of other plant varieties: Doing so keeps the blooms coming. A flowering plant's purpose is to propagate by producing flowers that then produce seeds. When you remove fading flowers before a plant starts producing seeds, it signals the plant to produce more flowers.
Deadheading has other advantages. For example, removing the fading flowers can make the plants look tidier. If you don't want sunflowers growing from seeds on their own in the same garden next year, then deadhead to prevent the seeds from forming and dropping into the garden soil.
When to Deadhead
As a general rule, deadhead flowers when they start to fade, or when they are damaged and no longer attractive, but do so before they produce seeds. When a sunflower's flower head stops looking as vibrant as it once did or when its yellow ray petals have fallen off, select it for deadheading. Also deadhead blooms that were chewed by insects or otherwise look withered. On multistem sunflower varieties, remove less-vigorous blooms to give other blooms more room to grow.
If you want to save the sunflower seeds that form in the center of the flower heads, then don't deadhead the blooms until their backs start to turn yellow, according to the University of Minnesota Extension website. After cutting off such a bloom, leave it in a dry, well-ventilated space to allow its seeds to mature. Depending on how late in the growing season it is, a sunflower plant may not produce new blooms after its seeded flower heads are removed.
How to Sanitize Your Tools
A sharp knife, scissors or a pair of hand pruners should do the job of deadheading sunflowers well. Because you're cutting plants that you want to remain alive and healthy, disinfect your cutting tools before you begin deadheading. If you don't, you could spread diseases from one plant to another. Make a solution that is one part bleach to three parts water, or a solution of that is one part rubbing alcohol to one part water. Soak your tools in the solution for five minutes, and then rinse them with clean water.
How to Make the Cuts
Deadheading sunflower blooms is fairly simple. Look down the stem from a bloom you want to remove, and locate the first set of leaves. If the sunflower is a multistem variety, look down a faded bloom's stem to find the location of a new lateral flower or stem. Make a slightly angled cut about 1/2 inch above the first set of leaves, new lateral flower or stem. Angle each cut so the remaining stem points somewhat toward the sky.
If the growing season is long enough in your area and your sunflowers continue to thrive, then you might get the chance to make yet another deadheading cut on the same plant, once again cutting the old growth back to the first set of leaves, new lateral flower or stem.