Decay

My brother-in-law's name has the initials D.K. and he was sometimes called that when he was young. As a schoolboy he sat in fear and trepidation as the dental nurse described to him and his fellow classmates how they should do all they could to avoid the terrible decay that would rot their teeth and make their lives a misery, given half a chance. He couldn't imagine why he would want to do that, or why anyone would think he might.
If you leave a sunflower unpicked right through winter, it will look like this.