It would depend on your zone and climate. A local garden supply would be your most accurate source of information.
I use scissors to cut the flower stem. Much neater then picking it.
I think she meant "choose" not pick. I thought she was asking what you thought too at first.
What zone are you in? Type your zip code in here:
What is the exposure? North? South? East? West?
where are u? shady,sunny,dry,humid,mountains,desert?? All most no plants really bloom all year,it's best to plant multiple plants of different kinds so they all bloom different times giving you year round colors
Roses are a great option, Lantana will begin in the later part of spring but will bloom through fall. Hydrangeas have a long blooming season as well.