For flower beds with large amounts of plants, like with cosmos, the best way to deadhead them is to cut back the entire group of plants at once. Again, you will want to wait until most of the blossoms on the plant has begun to die back.
With large areas of deadheading, where precision isn’t as important, you can use larger tools to make light work of it, such as a pair of grass clippers or handheld hedge trimmer.
Deadheading your garden can be a delightful task to take on during the summer. You can spend as much, or as little, time out in the garden just pottering about and tending to your plants in this way.
It’s vital work that helps to keep your garden plants vibrant but it’s not backbreaking and can actually be quite a relaxing pastime at the beginning or end of your day.