My Lemon Bush Leaves Are Turning Yellow & Falling Off

Nitrogen Deficiency

• A lemon bush that does not receive sufficient nitrogen exhibits symptoms of the problem on its oldest leaves, causing them to fade from green to yellow and gradually fall off. A bush that loses many of its leaves typically sees a reduction in fruit production. Although a soil test conducted before planting the bush indicates the nutrients it lacks, test the soil again when you encounter foliage problems. Ideally, you should provide each mature plant 1 1/2 pounds of nitrogen every year, split into three or four applications.

Magnesium Deficiency

• Magnesium deficiencies in the soil cause the lower ends of older leaves to turn yellow. The leaves feature yellow blotches on the foliage that gradually spread upward near the fruit unless remedied. Leaves that lose most of their color become susceptible to falling off during wind or rain. Because lemons thrive in soils with pH between 5.5 and 6.5, add 40 to 50 pounds of dolomite lime per 1,000 square feet to raise the current pH level and adjust the level of magnesium. Magnesium deficiency is also corrected with commercially produced magnesium sulfate.

Over watering

• Over watering a lemon bush is a common reason for leaf discoloration and premature leaf drop. The additional water around the roots prevents them absorbing oxygen, causing root rot that gradually causes foliage discoloration and drop. The problem is exacerbated when the lemon bush is planted in poorly draining soil. Transplant the bush to a spot with good drainage, if possible, or install underground drainage pipes that direct excess water away from your yard. Ideally, you should deeply water the root area of your lemon tree every seven to 10 days. Irrigate container-grown lemons when the top 2 inches of soil feels dry.

Other Factors

• Direct exposure to eight to 10 or more hours of direct sunlight causes the leaves of a citrus bush to pale, appear yellow and fall off. Because lemon bushes cannot stand temperatures lower than 20 degrees Fahrenheit, their leaves turn yellow when exposed to a sudden freeze. Diseases such as greasy spot and alternaria brown spot cause the leaves, in parts of in full, to turn yellow and fall off. Both the diseases favor damp conditions. However, you can control greasy spot with two applications of copper fungicide sprays -- in early summer and again during midsummer. Treat alternaria brown spot with three fungicide applications -- during early spring, when leaves fully expand and soon after petal drop.