Why Is New Growth on Hydro Seedlings Yellow?

Potassium

• Potassium deficiency causes yellowing of foliage and curling of the leaves. Stems will be soft and often droop. Older leaves will look spotty or burned.

Magnesium

• Magnesium deficiency is easy to spot in plants. Leaves will turn yellow, but the veins inside the leaves will remain green. Eventually, the leaf will begin to turn brown and dry. Unfortunately, symptoms don't show up until the deficiency is severe, so it often is too late to make much difference.

Iron

• A very common cause of yellowing in new plant growth is an iron deficiency. The problem usually presents as yellowing of new leaves, which may spread to other areas of the plant. Yellowing starts at the tips of the leaves or near their bases.

Manganese

• The symptoms of manganese deficiency are almost identical to that of iron deficiency. Plants will be almost completely yellow, especially in the advanced stages.

Nitrogen

• Nitrogen deficiency causes plants to turn pale green at first. Later, older leaves turn yellow. Finally, the yellowing spreads to young growth. It also causes stunted growth, especially in plant tops and roots.

Sulfur

• Sulfur deficiency is similar to that of nitrogen deficiency. Leaves turn yellow, especially older leaves. The stems become fibrous and tough. Stems grow longer, but do not get thicker.

Other Causes

• If leaves are deformed in addition to yellowing, it is possible that gasses such as ethylene are contaminating plants. If gas heaters are being used inside the greenhouse, provide adequate ventilation and check for leaks. One major problem in many hydroponic gardens is a lack of proper lighting. Insufficient light can cause pale or yellow leaves. Use a broad spectrum UV fluorescent light setup if the hydroponic garden has inadequate natural sunlight.