Answer: For all summer bloom, you will probably prefer to plant annuals. These bloom all summer long in a sunny location: petunia, zinnia, ageratum, red, blue, and white salvias, annual dianthus such as "Valentine" and marigolds. Some annuals that begin to bloom a bit later but continue very strong into the fall include cleome, cosmos, dahlias, and nicotiana.
Peonies are long lived perenials that bloom in late spring only; mums are often planted as seasonal plants and may become perennial but they will bloom in the fall only; narcissus bulbs will bloom in the spring and then go dormant until the following spring; and lotus are perennial but must be grown in water and bloom only at the height of summer. You could consider using some of these as accents to your annual plantings.
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