Water and Sunflower Growth

Basic Water Requirements

• The sunflower typically uses about 22 inches of water during its growing season. This is 15 to 20 percent less than corn. The sunflower can flourish in dry conditions due to its deep, aggressive root system, which is very efficient at drawing moisture from the soil.

Increased Watering During Flowering

• Although the sunflower can survive drought, water is critical for the plant in the weeks leading up to and following flowering. The sunflower is most dependent on water 20 days before and after flowering. Sunflowers that don't receive ample water during this time may become stressed.

Greater Water Extraction Ability

• The sunflower crop's water use can vary widely, from a paltry 8 inches to 38 inches per year. Due to their deep root systems, sunflowers can extract more water from the soil than many other crops. One National Sunflower Association study comparing the sunflower to proso millet -- which is primarily grown for feed grain or birdseed -- showed that while proso millet extracted about 4 inches of water from the top 3 feet of soil, the sunflower extracted about 7 1/2 inches of water from the top 6 feet of soil. The sunflower also has a unique water-trapping tool at its disposal. Its tall stalk, which grows to about 30 inches, traps snow during the winter which can add up to 9 inches of water to the surrounding soil.

More Water Equals Higher Yields

• The relationship between water use and sunflower yield is quite clear, according to the National Sunflower Association. For every inch of water use after the first 7 inches, the sunflower yields, on average, between 100 and 150 lbs. of seed per acre. Sunflowers growing in consistently dry conditions produce lower yields.

Too Much of a Good Thing

• While the sunflower needs a generous supply of water leading up to flowering through seed-head development, too much water during the plant's vegetative growth can lead to problems such as increased susceptibility to disease and a taller, weaker plant. Rainfall usually provides enough moisture for the plant, except in extremely dry conditions. The home gardener should take note and water the plants during extended dry periods and in the weeks leading up to and following flowering.