Lime trees comprise several species of tree and shrub of the rue family, Rutaceae. These trees are usually grown in tropical and subtropical countries for their edible fruits. Limes are important ingredients in pickles and chutneys, while lime juice is used in cooking, confectionery and flavored drinks. As with most plants, lime trees are also prone to certain conditions that may cause yellowing leaves.
Common reasons for lime leaves turning yellow
Nutrient deficiency
Lime trees need certain nutrients to thrive and stay healthy. Without these essential nutrients their leaves tend to turn yellow, while the veins may remain green. If the deficiency is severe, the veins will eventually turn yellow and the leaves will drop off. This yellowing is referred to as chlorosis, and is caused by a deficiency in nutrients such as iron, zinc and manganese.
To fix the problem, spray the trees with fertilizers that contain chelated zinc, iron and manganese to balance their nutrition. A good fertilizer for lime trees contains an NPK ratio of 2:1:1, where NPK refers to nitrogen, phosphorus and potassium. With a fertilizer like this, the trees will receive essential nutrients at the correct NPK ratio, along with small amounts of supplemental nutrients. Lime trees also prefer acidic soil, and sandy loam soil is ideal for them.
Incorrect soil pH
Incorrect soil pH may restrict the ability of plants to absorb certain essential nutrients. This could lead to yellowing leaves and nutrient deficiency. Lime trees thrive in neutral soil with a pH of seven. To increase soil alkalinity, calcium carbonate can be added to raise the pH. Inversely, to lower the pH if the soil is too alkaline, add sulfur or organic matter.
Overwatering
Overwatering could lead to nutrient leaching which may result in chlorosis. To ensure that you are not giving too much water to your in-ground plants, wait until the top four-to-six inches of soil feels dry to the touch. For container-grown trees, the top two-to-four inches of soil should feel dry before you provide enough water to soak the soil. Sandy loam is the ideal soil for lime and other citrus trees.
Pests
Lime trees could also turn yellow due to pest infestations. Whiteflies could invade the trees and feed on the sap of plant tissue. As they feed, they excrete a sugary substance called honeydew. The honeydew eventually grows mildew, blocking light from the leaves and resulting in yellow leaves that eventually fall off.
Asian citrus psyllids can also damage lime trees by attacking ripening fruits and resulting in blotchy yellow leaves. To exterminate these pests, spray them with strong jets of water or use insecticidal soaps and neem oil. You can also use their natural predators, like the Tamarixia Radiata wasps that prey on psyllids.
Diseases
Lime trees could turn yellow due to diseases such as root rot and Alternaria. Root rot is caused by the Phytophthora fungus, which lives in the soil. It can be triggered by overwatering, excessive rainfall or splashed dirt, but most often root rot is caused by poor soil drainage and overwatering. As the rot spreads to other plant parts, it causes yellowing leaves. Root rot can be treated by repotting the trees and adjusting the watering schedule as necessary.
Alternaria affects the trees’ young leaves and may cause brown and yellow spots. To prevent this fungal disease, the trees should be properly spaced apart to allow adequate air circulation.
Lime tree care
Lime trees are drought-resistant, but they do need regular care and watering. If they are left dry for long periods, their leaves may become droopy. These trees must be watered consistently; however, too much watering could also endanger them. Thus, establish a consistent watering schedule without watering obsessively.
These trees should be fertilized frequently since they are heavy feeders. Fertilize them every few months with a nitrogen-rich fertilizer or compost. Make sure to keep them warm, as they cannot tolerate temperatures below 50 degrees Fahrenheit.
Conclusion
Lime trees are drought-resistant plants that originated from India and some other regions of Asia and, like most plants, they can also be prone to conditions that cause yellowing leaves. The reasons for yellowing lime leaves could include nutrient deficiencies, pest infestation, overwatering, incorrect soil pH or fungal diseases such as root rot.
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