What Are a Sunflower's Preferred Conditions?

Soil Conditions

• Sunflowers tolerate a variety of soils well and will grow in anything from sand to clay, so long as the soil is well-drained. Insufficient nitrogen can limit growth, so home gardeners should ensure that there is an adequate supply of nitrogen, as well as potassium and phosphorus, in the soil. Sunflowers also prefer slightly alkaline soil, according to William L. Halvorson, principal Investigator for the U.S. Geological Survey based at the University of Arizona. Sunflowers do not tolerate salt well so care should be taken to test soil for high levels of salt prior to planting.

Water

• Sunflowers do not like wet or waterlogged soil, but they do require sufficient watering, as they are not efficient in their uptake and storage of water. Jill MacKenzie of the University of Minnesota Extension Service recommends that home gardeners ensure deep watering of about 1 inch per week for best growth.

Temperature

• Sunflowers grow best in temperatures ranging from 70 to 78 degrees Fahrenheit but will germinate at temperatures as low as 39 F and will continue to grow satisfactorily at temperatures as high as 91 F, although high temperatures may affect seed production.

Sunlight

• Sunflowers should be planted in full sun, well after the danger of frost. Once the plants are established, you will be able to observe their trademark characteristic: phototropism. The leaves and flower heads will follow the movement of the sun from east to west throughout the day.