Here are my two bibles, both available used at Amazon.
Taylor’s Guide to Annuals
Rodale’s Illustrated Encyclopedia of Perennials
To be accurate, there is both an annual geranium (pelargolum) and a perennial one (cranesbill).
Start reading; start admiring your neighbors’ gardens; start to talk to other gardeners, dig a small bed and plant something or several somethings.
Your sunflowers are annuals and planted yearly with seeds.
I found some perennial sunflowers, growing wild by the side of the road and adopted a few. Now I have hundreds and have to weed them.Here
I find myself on the verge of rewriting and illustrating a garden book so will reluctantly stop.
One of my perennial spring gardens here
Sunny spring garden here and here and here
Front garden in early summer: here