Why Are the Leaves on My Lemon Tree Losing Color?

Lemon trees

Lemon trees are 60 percent water, and the leaves on lemon trees are 70 percent water. Lemon tree growers should consider utilizing irrigation and rainfall to produce healthy, fertile plants. If your lemon tree is losing color, there are a number of factors that might be affecting the tree and its growth. They range from water requirements and nutrients to pests and root support.

Roots

The roots in a lemon tree are connected to the size and color of the branches and leaves. If the root system is damaged or not developed enough to support the tree, the leaves change color and eventually drop off the tree. Removing some of the branches, or shoots, can restore the balance between the roots and the tree top, allowing the tree to recover and flourish. Be sure to check to see if the roots are being affected by flooding, pests, disease, or over- or under-pruning the roots. All of these can affect the roots' ability to support the tree.

Water

Lemon trees lose color and foliage from both over- and under-watering the tree. Although it is important to utilize both irrigation systems and rainfall to produce healthy plants, a flood might harm lemon trees. Flood water drowns roots, keeping them from drawing the oxygen they need. The roots die without that oxygen, and the leaves begin to lose color and die. Flood damage also makes the roots susceptible to other diseases and pests, such as root rot and root weevils, respectively. Citrus groves need only one inch of water per week.

Winter and Freezing

Lemon trees are unprepared for freezing weather. As subtropical plants, they require temperatures above freezing. Healthy trees--those not affected by disease or insects that have a very strong root system--can recover after a freeze, but they still lose color and leaves. Unhealthy trees, however, in nonirrigated lands, can lose up to 90 percent of their leaves during freezing temperatures. In addition, older lemon trees lose their color during the winter months. The lower temperature prevents root growth and nutrient absorption.

Nutrition

Lemon trees require a balance of nutrients to improve their production and maintain their color. In order to keep their color, lemon trees need the appropriate salinity, gathered from soil fertilization. If a low-nitrogen fertilizer is used, root growth decreases as the top growth increases; however, a high-nitrogen fertilizer provides the opposite results. Choosing a fertilizer based on the individual tree's needs ensures the leaves do not discolor and the tree is healthy. If the tree is already healthy, choose a balanced fertilizer with neither a low nor high nitrogen content. If the veins in the leaves are losing their green color, a lack of zinc may be to blame. Also, iron deficiency and poor drainage affect the color of the lemon tree.

Insects & Pests

Maggots, aphids and other insects can affect lemon trees. Although the damage is aesthetic, the leaves do change color. Black sooty mold is an indication of pest infestation; this can be from aphids, white flies and scales. Although these pests usually do not affect the fruit on lemon trees, you can remove them by spraying the trees with insecticides or a strong spray of water.

References

• UBC Botanical Garden: Leaves Yellowing on My Lemon Tree
• Chron.com: Why Are My 'Meyer' Lemon's Leaves Turning Yellow?
• Master Gardeners San Diego: FAQ, When Should I Fertilize My Citrus Tree?
• University of Florida: EDIS, Citrus Tree Stresses: Effects on Growth and Yield