Lemon tree leaves turn yellow in temperatures lower then 50°F and due to a nutrient deficit in the soil. Both under watering and over watering can turn leaves yellow, as can spider mite infestations which cause small pin sized yellow dots on the leaves.
Yellowing lemon trees leaves is often associated with leaf drop but the tree can often be revived with the right care practices.
Keep reading to learn how to prevent leaves turning yellow and how to revive your lemon tree…
Over Watering Causes Lemon Tree Leaves to Turn Yellow
If there is too much moisture around the roots of your lemon tree, this can cause the leaves to turn yellow as a sign of stress.
Lemon tree leaves turn yellow as a result of:
- Over Watering. Lemon trees grow best when the top two inches of the soil becomes somewhat dry before watering which typically means watering once per week with a generous soak. If you are watering too frequently so that the soil is consistently moist then this causes the leaves to turn yellow (and potentially drop) and promotes the conditions for the fugal disease root rot which can kill the lemon tree.
- Pots without drainage holes in the base. Lemon trees should be grown in pots with drainage holes in the base so that excess water can escape after watering and the soil can dry somewhat between bouts of watering. Some decorative pots do not have drainage holes which causes the soil to become saturated and cause s the leaves to turn yellow.
- The use of trays underneath pots to prevent water spilling indoors. Trays that are placed underneath lemon trees should be emptied of excess water regularly as the water can keep the soil damp and prevent proper drainage.
- Slow draining soils. Lemon trees require well draining soils to prevent leaves turning yellow and leaf drop. The optimal soil mix for potted lemon trees is 1/3 multi purpose compost, 1/3 garden compost and 1/3 horticultural grit or perlite for nutrients and to ensure good drainage so that the soil can dry somewhat around the roots to prevent the leaves turning yellow.
Lemon trees may require more or less frequent watering, depending on the climate.
In dryer climates it may be necessary to water more often whereas in humid climates or climates with more rainfall lemon trees require less frequent watering.
Adjust the frequency of your watering so that the top two inches of the soil dry out somewhat between bouts of watering and the lemon tree should revive as this is the correct balance of moisture.
The yellow leaves may drop off but with consistent care and good watering practices, the leaves should regrow.
(To learn how to establish the correct watering frequency for lemon trees for your climate, read my article how to water lemon trees).
Drought Can Cause Lemon Tree Leaves to Turn Yellow
Whilst lemon tree leaves more often turn yellow from over watering as they prefer soil conditions more on the dry side, leaves can also turn yellow as a reaction to drought.
If the leaves look shriveled as well as yellow then this is a clear indication that drought is the cause.
Drought that results in lemon tree leaves turning yellow can occur for several reasons:
- Indoor lemon trees leaves turning yellow. The air in houses is typically much dryer then outdoors with sources of heat, air con and forced air all sapping moisture way from the lemon trees leaves causing them to turn yellow as a sign of stress. Locate your lemon tree away from draughts or sources of heat, (ideally in a sunny window) and mist the leaves regularly to improve the micro-climate for your lemon tree.
- Watering lemon trees too lightly. If you water the lemon tree too lightly then the surface of the soil may be moist but the water does not infiltrate the soil to the roots where it is required, causing the leaves to turn yellow. Water the lemon tree with a generous soak once per week so that a trickle of water emerges from the base of the pot.
- Intense heat and sun can drive evaporation. Potted lemon trees in particular have a limited capacity for soil and therefore less moisture so they are prone to drying out in intense heat. Careful monitoring of soil moisture is required during heat waves to prevent drought and if necessary, water the lemon tree more frequently to prevent leaves turning yellow.
Water your lemon tree generously at least once per week in the growing season, misting the leaves regularly to maintain some humidity and your lemon tree can recover.
For lemon tree that has suffered from significant drought, I recommend submerging the entire pot in water in a basin or wheel barrow full of water for around 10 minutes.
When soil become very dry it can bake hard and cause water to run off the surface rather then reach the roots which exacerbates the problems associated with drought.
If your lemon tree is planted in a garden boarder, use a soaker hose to thoroughly water the ground, so that the moisture can reach the roots.
(For more information read my article why are my lemon tree leaves curling?)
Yellow Leaves due to Lack of Fertilizer
Lemon trees are relatively heavy feeders and grow and produce fruit to their best when with regular feeding throughout the Spring and Summer.
If the lemon tree has a deficit of nutrients then the leaves start to droop and turn yellow sometimes with retaining green veins with the rest of the leaf yellowing (chlorosis).
This is particularly common for lemon trees in pots as pot have a limited capacity for soil and therefore less nutrients for the roots to uptake.
The solution is to apply a specialized citrus fertilizer once per month during Spring and Summer to keep the leaves looking healthy and to promote flowers and developing fruits.
Regular applications, of fertilizer, good watering practices and full sun should help the lemon tree recover from a drooping appearance with yellow leaves over the following weeks.
However do not be too heavy handed as too much fertilizer can also cause the leaves to turn yellow, so always follow the manufactures instructions diligently.
Low Temperatures can Cause Lemon Tree Leaves to Turn Yellow
Lemon trees are native to warm tropical climates and do not tolerate cold Winter temperatures or frost. (USDA zones 9-11)
Stress from low temperatures can turn the leaves of your lemon tree yellow and drop off. If the lemon tree experiences frost it can die back.
Mature lemon trees tend to be more cold hardy then younger trees so, a smaller lemon tree is more vulnerable to cold and their leaves turning yellow and dropping.
However lemon trees of all varieties should be brought indoors or to a heated greenhouse when the night temperature is as low as 50° F (10°C) and placed in a sunny window for protection and to retain the leaves.
This however can lead to problems such as leaf drop when they are brought indoors, so I wrote another article explaining how to mitigate leaf drop when bringing lemon trees indoors for Winter.
With reduced hours of sunlight and at a lower intensity, lemon tree leaves do tend to lose their green color and some may drop off.
However if the lemon tree is in a sunny window with good watering and you regularly mist the leaves, it should make a recover with new growth emerging in the Spring in response to more light.
Yellow Spots on Indoor Lemon Trees
If you notice small pin sized yellow spots on your lemon tree leaves and perhaps some leaf drop then this is because of spider mites.
Spider mites thrive in homes due to the lower humidity and can be a common pest for house plants.
If left untreated spider mites can defoliate your lemon tree, but fortunately the are a relatively easy pest to deal with.
Misting with water is a good disincentive as they thrive in dry homes and moist foliage can help to displace them.
However to get rid of them all you have to do is wash your leaves with soapy water and you can rid the lemon tree of the infestation.
This may take several applications to completely eradicate them but it is a very effective treatment.
Trim back any several affect leaves and the lemon tree should recover without a problem.
Lack of Sun can Cause Yellowing Lemon Tree Leaves
Lemon trees are native to tropical climates and are cultivated extensively in countries such as Spain and Mexico in full sun.
Lemon trees can be cultivated by gardeners outside of their usual range but it is essential that they are grown in full sun or they may fail to flower, fruit and the leaves can turn yellow and drop off due to stress.
So it is important to locate your lemon tree in the sunniest area of your garden to get the best yield of fruit and for the plant to stay healthy.
Problems frequently occur when the lemon tree is brought indoors for protection from frost as it has to contend with:
- Less hours of sun.
- Lower intensity of light.
- Lemon trees indoors are more shaded and need to acclimate to the indoor conditions.
All of these factor can cause leaf drop or a yellow of the leaves.
The best place for a lemon tree in Winter is a heated green house as it has a consistent temperature and the maximum amount of natural sun.
However they can survive as long as you put them in a sunny south facing window with lots of light.
Some yellowing of leaves and leaf drop may still occur due to the seasonal change an reaction to less light in Winter but if the lemon tree is in a sunny window then it should recover with new leaves emerging and any yellow leaves should look much healthier in the spring.
- The reason lemon trees turn yellow can be because of under watering or over watering and as a reaction to low temperatures. A lack of nitrogen or sunlight can also be responsible for lemon tree leaves turning yellow.
- Yellow pin sized spots on lemon tree leaves are caused by a spider mite infestation.
- Yellow Lemon tree leaves with green veins are due to a lack of fertilizer.
- Locate lemon trees in full sun, mist the leaves regularly, protect them from temperatures colder then 50° F (10°C), feed them in the Spring and Summer and water once per week with a good soak and the lemon tree leaves should recover from a yellow appearance to a healthier green leaf.