First, incorporate as much thoroughly decomposed organic material (e.g., compost), as possible into your sandy soil. At least 4 to 6 inches tilled into the top 8 inches of soil will improve your beds immensely. While you are adding material, consider making these raised beds, it will save you lots of work in the years ahead. See this Web site: Raised Beds. You do not say if you desire to plant perennials, annuals, or a combination of each. So here are some of each:
Perennial : Blue Plumbago; Firespike (Odontonema strictum); Texas Gold Columbine; Asparagus Fern; Turk's Cap; Purple Heart (Setcresia pallida); Rosemary; and Mexican Petunia (Ruellia sp.).

Annuals: Impatiens; Begonias; Coleus; Flowering Tobacco (Nicotiana); Caladiums; Johnny Jump-up Violas; and Red Salvia (Salvia splendens).

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