United States 
Have A arber That Has Has Two Planter Boxs On Each Side. Looking For A Perennial that will flower from spring To Fall. Live In The south East U.S. Zone 7.
31 Dec, 2011
Answers
Welcome, Whirlybrd02!
How about:
Blanket Flower (Gaillardia aristata)
Lance-leaf Tickseed (Coreopsis lanceolata)
Gaura, tall kinds (Gaura lindheimeri)
Missouri Coneflower (Rudbeckia fulgida)
Assuming that you meant herbaceous perennials
31 Dec, 2011
Most important is how big the planter boxes are - if they're shallow troughs, say, no deeper than a foot, you're restricted to plants which only get a maximum of 2/2.5 feet.
1 Jan, 2012
Some veronicas flower for ages, or if a small shrub would do then potentillas flower longer than just about any other.
1 Jan, 2012
Have you thought of ruddbekia - various colours yellow to deep red, large daisy like blooms and flower forever? Dead-heading not necessary, just as you are passing. Herbaceous perennial, clumps can be split in late autumn after cutting down. Loved by bees. Likes full sun but does need a good water once a week and feed once a month. Can grow up to 2m, including flower head. Surprisingly shallow rooted for such a prolic flowering plant.
2 Jan, 2012
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