Answer: Even though the weather has been hot, you have probably been overwatering. Sunflower seeds have large, deep roots and can tolerate droughty conditions and heat. By watering frequently you've encouraged the roots to remain in the upper part of the soil where they become reliant on frequent watering. If you water deeply only twice a week, the roots are forced to grow deeper where the soil is cooler. Try planting seeds again but this time water deeply but infrequently. If you choose the smaller varieties of sunflowers they will still have time to grow and flower for you this summer.
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