noun / verb
deadhead
DED-hed/dˈɛdhˌɛd/
A faded flower to be removed from a plant.
The clipped deadhead lies beside the plant and a pair of pruning snips.

Etymology
The supplied evidence describes a non-paying passenger or spectator and a Grateful Dead fan. It does not explain the botanical use for a faded flower head removed from a plant.
More examples
- I deadhead the roses once their petals begin to fall.
- We deadheaded the marigolds before watering the garden.
- A few deadheads remain among the fresh blossoms.
Forms
deadhead · deadheads · deadheaded · deadheading