Reasons for Yellow Leaves and Leaf Drop in Lemon Trees and How to Fix Them

Don't panic if your lemon tree (Citrus limon) has yellow leaves and is dropping them! Find the cause and treat it accordingly, and it will soon recover its vigor~Here are some very practical solutions, easy enough even for beginners!

1. Water Problems 

1. Waterlogged roots and root rot

Symptoms: lower leaves turn yellow first and drop at a touch, leaf tips turn brown, potting soil is sticky and wet

First aid: stop watering, take the plant out of the pot and cut off the rotten roots (the blackish-brown, mushy ones), and repot in fresh leaf mold soil+perlite at 3:13:1), lay a layer of clay pebbles at the bottom of the pot to prevent waterlogging, and let the plant recover for 1week without watering.

2. Underwatering and drying out
 
Symptoms: leaves curl and become brittle, new leaves turn scorched yellow, potting soil is dry and cracked

First aid: first water lightly around the edge of the pot, then water thoroughly after 10minutes; mist the leaves 1-2times a day to raise humidity; in summer, water whenever the top 2cmof the potting soil is dry.

2. Nutrient Deficiencies

1. Iron deficiency/Magnesium deficiency

Iron deficiency: new leaves have green veins and yellow tissue between them (like a yellow net pattern); spray with a 0.2%ferrous sulfate solution (1liter of water+2g), once a week.

Magnesium deficiency: edges of old leaves turn yellow in an inverted “V”shape; water with a magnesium sulfate solution (1liter of water+3g), or bury well-rotted bone meal in the soil.

2. Not repotting for a long time

Symptoms: the whole plant has dull yellow leaves, grows slowly, and the potting soil is compacted.

Solution: repot every spring, using nutrient soil+well-rotted sheep manure (5:1), bury slow-release fertilizer as a base fertilizer, remove 1/3of the old soil while keeping the soil around the roots.

3. Environment, Pests and Diseases

1. Insufficient light

Symptoms: leggy branches and leaves, thin yellow leaves, few flowers.

Solution: move it to a south-facing balcony and make sure it gets at least 6hours of direct sunlight a day, with slight shading at noon in summer.

2. Spider mites/Scale insects

Spider mites: small white spots on the undersides of leaves+curled leaves; spray with bifenazate, covering both sides of the leaves.

Scale insects: white/brown bumps on the branches and trunk; spray with buprofezin, or wipe the insects off with an alcohol swab, then repeat once after 5days to reinforce the treatment1more time.

4. Key Points for Daily Care
 
1.For fertilizing, use monopotassium phosphate (1:1000), applying weak fertilizer frequently; never use unrotted organic fertilizer, which burns the roots.

2.In northern regions, water with citric acid water once a month (1liter of water+1ml) to acidify the soil, or bury ferrous sulfate to prevent alkalization.

3.When new leaves turn yellow, stop fertilizing first; once acidity is adjusted and watering is under control and the plant has recovered, resume fertilizing; for severely affected plants, prune weak branches+change the soil and disinfect.
 
In short, if you follow these methods, the yellowing and leaf drop will soon improve.