Does Growing Sunflowers Require a Lot of Watering?

Water Needs

• Sunflowers are known to use more water than most other crops, including corn. According to the Purdue University Alternative Field Crops Manual, sunflowers used an average of 228 grams of water per gram of soil more than corn in a single growing season. The plants do not distribute water efficiently. The long stem ending in the large flower heads create an uneven surface over which the plant has to distribute its water intake, so the plant needs to push more water upwards constantly. Because it grows best in full sun, the plant also tends to inhabit high temperatures and therefore needs more water.

Drought Tolerance

• Despite its need for constant watering and inefficient use of the moisture it has, the sunflower is considered highly drought-tolerant. This is because the plant produces long, thin roots that can flow far out and down from the base of the plant. These roots allow the sunflower to absorb moisture from areas of the soil almost 7 feet from the plant, enabling it to provide itself with the water it needs. The 20 days before and 20 days after flowering are the most important for water stress. During this time, the sunflower needs irrigation; otherwise, it can generally fend for itself.

How to Water

• Always water the soil before sowing a sunflower seed, and keep it consistently moist until you see sprouts appear. Under proper conditions, a sunflower seed will germinate within 10 days. Beyond this period, dig a moat 18 inches out from the base of the plant and 4 inches deep. Fill this moat once per week until the water stops absorbing into the soil; the excess water will be absorbed as the sunflower uses up what it's already taken in. Keep the watering at least 18 inches away from the base of the plant, however, as soaked soil around the base can lead to rotting and fungus.

Other Tips

• If you use a liquid fertilizer, mix that into the water every time you fill the moat to apply the necessary nutrients to the soil. This is especially important in early spring, when most of the growth is taking place. A 3- to 4-inch-layer of organic mulch around the base of the sunflower will help the soil retain moisture and insulate it from temperature changes that can evaporate some of the moisture.