Yellow Seedling Sunflower Leaves

Infections

• Viral and bacterial infections are among the most common causes of leaf yellowing in young and established sunflower plants. They are frequently most problematic during periods of heavy rain or when growers over-water. If soil doesn't drain well enough, standing water will damage roots and make it difficult to transport nutrients and water to the plant, most often causing yellow leaves. Root rot is a common result of too much water and is caused by bacteria entering the root system. Sunflower rust is another bacterial infection and is indicated by cinnamon colored pustules on the leaves. In the early stages, these spots may give the leaves a yellowish hue.

Nutrient Deficiency

• Shortages of both nitrogen and iron will cause leaf yellowing. Both elements are essential in chlorophyll production, which is necessary to maintain overall plant health and food production. Iron chlorosis will present with yellowing that starts at the edges and moves inward, while nitrogen deficiency will have a more uniform, all-over yellowing. The treatment for iron chlorosis involves amending the soil with iron chelate, and both can be addressed with a heavy mix-in of organic matter compost.

Fertilizer

• Liquid chemical fertilizers are a cause of leaf yellowing. If over-used, fertilizers may damage roots, which leads to leaf scorch. This yellowing will occur around the edges of leaves and grows over time. The amount of damage depends largely on the amount of damage done to the roots; some cases will present with only minor yellowing on parts of the plant, while more serious damage will cause all leaves to change. Growers should closely follow application instructions for fertilizer to prevent damage and consider using compost to amend soil drainage and fix nutrient deficiencies.

Water

• Over-watering, particularly in soils that don't drain well, will create ideal conditions for overgrowth of bacteria and fungi. Standing water also causes root suffocation, which may cause leaf yellowing and plant death. Under-watering increases stress, which may turn leaves yellow and make them drop prematurely and, if left untreated, will cause death of the plant. Sunflowers should be provided nutrient-rich soil that drains well. The soil should be kept moist, not wet, a factor that is especially important during the summer because sunflowers require full sun to thrive.