Answer: Unfortunately I can't think of any perennial that will really bloom all summer. Most of them bloom for only a few weeks at a time. I suspect you would be happier with an annual instead. However, for a sunny location, the verbena "Homestead Purple" is very short and spreading, will bloom for months and months until frost, and can also be planted in containers. Its drawback is that it is not always hardy north of zone 7.
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