What is the best perennial flowers to plant to have blooms all season?

Janet, it would help if you let us know what Region you live in since that matters so much. Since I don't know that, I would suggest you ask at your local garden center since they stock plants native to your area for the best success.

What is your location and lighting?

Depends on if you have sun or shade. For sun, I like day lilies, lamium, or balloon flowers. For shade, I prefer a foliage plant with color, like snow-on-the-mountain.

It would help if you gave your location, Janet. However, for Shrubs, Hydrangea are one of the best, in my opinion! They bloom all Summer and into late Fall. As far as flowers, there are so many - again, it depends on your location and where your flower beds are situated ... are they in shade or hot sun. Regarding Perennials, most do have a "blooming cycle" ... in other words, they may not bloom "all season long" as you request but still contribute plenty of color to a garden. One of the toughest plants I like is Russian Sage. It has a tendency to spread but is eadily controlled by pulling up the tiny shoots as they appear. Russian Sage blooms mid Summer right through to late Fall, is a lovely, airy plant with lilac colored blooms and is about 2' to 3' tall. I saw an entire garden bed planted with Russian Sage last year and it was stunning ... it looked like a mauve-colored cloud had landed in the yard! Echinacea starts blooming mid Summer. Rose Campion is a prolific bloomer (it spreads too!). If you Google "bloom times of Perennials" you will see many, many choices too numerous to type here. Again, make sure you know your gardening zone for best results.

Daylillies are my favorite

Need to know how high you want the flowers...or if you want your whole garden in perennials ..and where do you live ??

Hydrangea!