While there are a few varieties out there that promise endless flowers without the trouble of deadheading, most plants require you to dead-head them for a for a reliably long bloom period. Picking off flowers that have passed their peak stops seed heads from forming and prevents the plant from receiving a signal that its work is over. Snap off large flowers with your fingernails. For small blossoms, or hanging plants gone straggly, shear them back by half with scissors. Wait a week, and cut off the remainder. You’ll be rewarded with a new crop of flowers and tidier plants, especially if you follow up with a light feeding.