If you want to prolong those flowers in your garden which are still blooming, then you need to keep deadheading!
Keep Deadheading
Why would you cut off all the lovely flowers on your Pelargoniums?
Why would you cut off all these lovely flowers on your Pelargoniums when they are in full, glorious bloom?
Should you deadhead your Rhododendrons?
Deadheading prevents the flowers from going to seed and rhododendrons should be deadheaded too in order to give the plant energy for more flower production next year. Deadheading will also give your rhododendron a tidier appearance until next year's flowering period.
The Pink Wheelbarrow 