Answer: Gerbera daisies are most reliably grown from purchased plants set into the garden in full sun with a rich soil and regular watering. They really like long days and hot weather and may slow down by that late in the season.
You might consider dahlias which are very fine for cutting and come in all sorts of colors, shapes and sizes, plus some of the more reliable later annuals such as cosmos (pinks, yellows, white) , tithonia (orange), salvia (red and blue), zinnia (all shapes, colors and sizes), and gloriosa daisies (gold and autumnal tones).
Good luck with the flowers!
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