Lemon trees and their fruit are, for me, the highlight of any Summer. I use my homegrown lemons for cooking and making a refreshing glass of lemonade, which is a hit with every BBQ guest!
But, in the very first 2 years of growing lemon trees, to my horror, my potted lemon tree leaves turned yellow despite watering diligently and thoroughly every week. What had happened?
Even more embarrassing is that I work at a garden center! So, I launched an investigation to diagnose exactly why my lemon tree leaves were turning from green to yellow, and I was eventually able to adjust the care and conditions for my lemon tree so that their leaves stayed a healthy green (just FYI, if the leaves have already turned yellow, they typically fall off as mine did before regrowing in the Spring).
In this post, I’ll share with you all my tips to help you diagnose the problem with your lemon tree and guide you step-by-step to the solution to prevent your leaves from turning a sickly yellow.
Want to cut to the chase? Lemon tree leaves turn yellow in temperatures lower than 50°F and due to a nutrient deficit in the soil. Both underwatering and overwatering can turn leaves yellow, as can spider mite infestations, which cause small pin-sized yellow dots on the leaves.
I have now personally identified and dealt with all these problems for my own lemon trees and my customers.
Keep reading to learn how to prevent leaves turns yellow and how to revive your lemon tree…
Is the Soil Damp? Overwatering Causes Your Lemon Tree Leaves to Turn Yellow
So, I think it is important for us to remember that our Lemon Trees are native to warm climates with full sun and prefer the soil to dry out somewhat between bouts of watering.
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.
From my research, The technical reason is that too much moisture around the roots of your lemon tree excludes oxygen from the soil, which prevents root preparation.
If the roots cannot respire, then they cannot update moisture (ironically!) or nutrients from the soil, and without nutrients or moisture, the leaves turn yellow and eventually drop off!
But you might be thinking, “But I am only watering my lemon trees once every week…overwatering cannot be the problem!” But there are some other considerations that we need to think about that may be keeping the soil too damp (and therefore causing your lemon tree to turn yellow):
- 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 causes the leaves to turn yellow.
- The use of trays underneath pots to prevent water from 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 from 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 from turning yellow.
Lemon trees may require more or less frequent watering, depending on the climate.
How do you know if your lemon tree needs watering? As I said I typically water my potted lemon trees once per week in Spring and Summer, but I don’t like generic advice as how often you water your lemon trees should depend on how quickly the soil dries out rather then a specific timeframe.
I personally use my finger to feel the top 2 inches of the soil. If the soil is damp, I’ll leave watering for a few days, but once the soil feels as if it is just drying out, I give my lemon trees a generous soak.
This means I can strike a balance between meeting the lemon trees’ watering requirements whilst avoiding the problems associated with overwatering and risking the leaves turning yellow.
I should emphasize that 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.
So what you need to do is to 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.
Whenever I have had to do this, the yellow leaves drop off, but with consistent care and good watering practices, the leaves regrow in the spring.
For any boggy, low-lying gardens with slow-draining clay soil, I recommend that you plant your lemon trees in pots. With pots, you can customize the soil to meet the lemon trees’ preferences. I can tell you from experience (and a bad back!) that this is much easier and more effective than trying to amend garden soil for your lemon trees.
Expert Tips: Struggling with yellow leaves due to damp potting soil because of high rainfall? Replant your lemon tree into a clay or terracotta pot and be more heavy-handed with the horticultural grit (I’ve used as much as 40% grit to 60% compost before). For people growing lemon trees in rainy climates, I always recommend planting the trees in clay and terracotta, as the pots are breathable and allow your potting soil to dry out more evenly. I can say from experience that this is a very effective way to mitigate root rot and keep your lemon tree leaves a healthy green rather than a sticky yellow!
(To learn how to establish the correct watering frequency for lemon trees for your climate, read my article How to water lemon trees).
Is The soil Too Dry? Drought Can Cause Lemon Tree Leaves to Turn Yellow
So we’ve discussed what happens when the soil is too damp. But what if the soil is too dry? Whilst lemon tree leaves more often turn yellow from overwatering as they prefer soil conditions more on the dry side, leaves can also turn yellow as a reaction to drought (this is what happened to me!).
If the leaves look shriveled as well as yellow then this is a clear indication that drought is the cause.
As we discussed with overly damp soils, dry soil that results in lemon tree leaves turning yellow can occur for several reasons rather than just underwatering:
- Indoor lemon tree leaves turning yellow. The air in houses is typically much dryer than outdoors, with sources of heat, air con, and forced air all sapping moisture away from the lemon trees’ leaves, causing them to turn yellow as a sign of stress. What you need to do is to 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 or use a humidifier (which is what I use as it is much more convenient).
- 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 from turning yellow.
When I lived in a much hotter and dry climate (Southern California), my lemon tree suffered in Summer because it was backed in the sun every day with little rainfall. The sun was so intense that the soil dried up before the lemon tree’s roots could draw up the moisture it needed, so even watering more regularly wasn’t really working. The leaves were turning yellow and curling.
So what was the solution? I replanted my lemon tree into a larger pot. The larger pot has a greater capacity for soil and, therefore, can hold moisture so that it doesn’t dry out as quickly.
I usually pot my lemon trees with 1/3 garden compost, 1/3 leaf mold (composted leaves), and 1/3 grit, but being in a hotter climate, I decided to experiment and repot my lemon tree with a higher proportion of leaf mold (probably about 50% leaf mold with 25% compost and 25% grit).
As I was in a particularly hot climate, I decided to increase the proportion of leaf mold as leaf mold can hold up to 500 times its own weight in moisture (more so than any other potting medium), so my lemon trees potting mix didn’t dry out instantly in the sun as it once did.
The results were that the soil took 5-7 days for the top 2 inches of the soil to dry, which was great! My lemon tree was much healthier and the leaves didn’t curl up to anywhere near the same extent even in the hottest days of the year!
I would etsablish how long it takes for the top 2 inches of your lemon trees potting mix to dry and then water your lemon tree generously (usually at least once per week in the growing season). For indoor lemon trees misting the leaves regularly to maintain some humidity can help your lemon tree recover.
My friend had a lemon tree with curling leaves due to drought stress and what I noticed when they watered it, is that far too quickly, the water trickled off the surface and down the side of the pot, emerging from the drainage holes in the base of the pot.
I felt the soil’s surface, and I discovered it had baked hard, and water was repelling off the surface rather than infiltrating. I picked up the pot to assess its weight (it should feel nice and heavy if the soil is evenly moist), and the pot was very light, indicating the soil was just not absorbing the water properly.
So what we did was to fill a wheel barrow half way with water and lift the lemon tree into it and left i t there for 30 minutes.
By the time was came back it was clear from the weight of the pot that the soil had a chance to properly draw up the moisture and the soil around the root ball felt evenly moist which is exactly what we are looking for.
I understand that it may not be the most practical thing to do but it worked and once the soil had been soaked, as long as you water it consistently (and avoid it drying out altogether), the soil shouldn’t bake hard in the same way and moisture should infiltrate the surface more effectively. How do you stop this from happening again?
Pro tip: To prevent the sun from baking the soil dry again, I recommend regular watering and placing a 1-inch layer of pebbles over the surface of the soil. This prevents the sun from beating down on the soil directly, keeping it cooler, lowering evaporation, and preventing it from baking hard again. I personally prefer to use white stone mulch, as this reflects light, increasing the brightness around the tree and absorbing heat off the soil.
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?)
Not Enough Nutrients? Your Yellow Leaves Could be due to a Lack of Fertilizer
Our 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).
I only really see this with lemon trees in pots, as pots have a limited capacity for soil and, therefore, less nutrients for the roots to uptake, but it can happen in sandy soils.
Has your lemon tree been in the same pot for a long time? Then, it has probably exhausted the soil’s nutrients, which is why the leaves are turning yellow. If it is in early Spring or fall, I would recommend repotting your lemon tree in a larger pot with new soil, which should have lots of nutrients.
Important tips: Always plant your lemon trees in a nice deep pot. Lemon trees have deep roots and, therefore, prefer to grow in a nice deep pot.
As we discussed, my favorite potting medium is equal parts garden compost, leaf mold, and perlite to create the optimal balance of nutrients, soil structure, and drainage.
If you’re already in the late Spring or Summer, then 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 fruit development.
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.
When I’ve done this myself, often I find the yellow leaves fall off, but new growth soon emerges and the tree looks green and healthy.
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 Your Lemon Tree Leaves to Turn Yellow
As we talked about, our lemon trees are native to warm tropical climates and do not tolerate cold Winter temperatures or frost. (USDA zones 9-11)
What happens is that 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.
What I have personally observed is that if the temperatures are only slightly too cool (under 50 degrees f (10 degrees C), then leaves turn yellow, but if there is a sudden drop in temperature, the leaves tend to just fall off.
Mature lemon trees tend to be more cold hardy, than younger trees so, a smaller lemon tree is more vulnerable to cold and their leaves turning yellow and dropping.
Pro tip: Whenever you buy citrus trees or even olive trees, choose the most mature tree with the thickest trunk. The trunk thickness is directly correlated with resiliance to cold. Skinny spindly trees tend to fare worse in cold temperatures.
However, we need to remember, 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, in my experience, it should make a recovery with new growth emerging in the Spring in response to more light.
Do You Have Yellow Spots on Your Indoor Lemon Trees?
If you notice small pin-sized yellow spots on your lemon tree leaves and perhaps some leaf drops, 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, from experience 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 affected leaves, and the lemon tree should recover without a problem.
My best tip is to use a humidifier if this is a consistent problem for you. As soon as my friend started using a plant humidifier, they stopped having issues.
If you wait until Spring, then new green leaves should regrow if the yellowing leaves have dropped off.
Is Your Tree in the Shade? 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.
But do we need to live in these hot climates to grow lemon trees? Fortunately, no! Lemon trees can be cultivated by gardeners outside of their usual range, but they must be grown in full sun. Otherwise, they may fail to flower or fruit, and the leaves can turn yellow and drop off due to stress.
So, it is important that we locate our lemon trees 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:
- Fewer hours of sun.
- Lower intensity of light.
- Lemon trees indoors are more shaded and need to acclimate to the indoor conditions.
All of these factors can cause leaf drop or a yellow of the leaves.
Are your lemon trees planted in the garden? In that case, I would look to trim back any overhanging tree limbs or shrubs that could be casting shade on your tree.
In my experience, the best place for a lemon tree in Winter is a heated greenhouse, as it has a consistent temperature and the maximum amount of natural sun. But this can be very expensive.
However, they can survive as long as you put them in a sunny south-facing window with lots of light. Mine grows very well in a glass porch at the front of my house.
Some yellowing of leaves and leaf drops may still occur due to the seasonal change and reaction to less light in Winter, so I wouldn’t worry about it too much, 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.
Mine always looks a little worse for wear when it has been inside all winter, but it soon perks up in the spring when it’s moved outside and new green leaves emerge in the sun!
(Read my article, how to revive a dying lemon tree).
Do you have any questions about lemon trees? Or any experience you’d like to share? Do you have any specific concerns? Please Let me know in the comments below, and I’ll help you solve it!
Key Takeaways:
- Lemon trees can turn yellow due to underwatering or overwatering or as a reaction to low temperatures. A lack of nitrogen or sunlight can also cause lemon tree leaves to turn 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 than 50° F (10°C), feed them in the Spring and Summer, and water them once per week with a good soak. The lemon tree leaves should recover from a yellow appearance to a healthier green leaf.