Fix Yellow Leaves and Spots on Lemon Trees (6 Ways)

My parents have a lemon tree that occasionally gets yellow leaves on it. We didn’t think much of it at first, but we noticed it got worse and some of the leaves fell off. So, I did some research to help them out. Here’s what I found.

Lemon trees get yellow leaves from over-watering, extreme weather, improper nutrients, transplant shock, and pests and diseases like aphids and root rot. To fix, only water when the soil is dry and provide high nitrogen fertilizer. Grow in USDA zones 9-11 and move potted lemon trees indoors during extreme weather.

If your lemon tree is getting yellow spots, it’s likely from nutrient deficiencies, root rot, or a disease called greasy spot (more on these later).

While lemon trees get yellow leaves from several causes, how can we tell which issue is causing it, and from there—how can we fix it? Let’s take a closer look.

1. Over-Watering

Over-watering is the most common reason lemon trees get yellow leaves, and there are two types (depending on the soil’s drainage).

Soil Drainage	Caused By	What It Does
Fast	Too sandy or rocky soil	Leaches nutrients from the soil
Poor	Clay or compacted soil	Pools water and drowns the plant’s roots (waterlogged)

Too much water in fast-draining soil strips the nutrients from the soil by pushing them further down (also called leaching).

On the other hand, over-watering with poor drainage creates waterlogged soil and stresses the tree. Both lead to yellow leaves.

Before addressing the soil’s drainage, let’s start with the ideal way to water lemon trees.

The best way to water lemon trees is to only water when the first 2-4 inches of soil is dry. I check this by pushing a finger into the soil. Make sure to soak the soil down to at least 2 feet as 90% of the roots are found at this depth.

How to Test Soil Drainage

If you’re unsure if your soil is draining too fast or too slow, consider doing a percolation test.

Here’s how to do one:

1. Dig a 1-foot by 1-foot hole
2. Put a yardstick in it and fill it with water
3. After an hour, measure the amount of water drained on the yardstick

When digging a hole, make sure to dig outside of the drip line (canopy) of your plants to avoid damaging their shallow roots.

Also, consider digging up to 3 holes around your property as there can be vastly different soil types depending on the location.

Ideally, the soil should drain at a rate of around 2 inches per hour.

However, this is a guideline and not a rule, so don’t worry if yours is off. This test is primarily to determine if your soil drainage is excessively too fast or slow.

How To Fix Soil Drainage

Fortunately, the solution for poor and fast-draining soil is the same. Increase the organic matter (compost) of the soil! This is because organic matter both breaks up larger clumps of soil and retains the proper amount of moisture.

For example, every 1% increase in the soil’s richness leads to an additional 20,000 gallons of water held per acre.

I recommend applying 2 inches of compost every 1-2 months under your lemon tree’s drip line.

Once your soil has proper drainage, apply 4-12 inches of mulch to reduce evaporation, regulate soil temperature, and prevent soil erosion. This also helps feed the lemon tree.

If you’ve checked your watering and drainage, and it seems right, what do we look for next?

2. Extreme Weather

Hot Weather

Lemon trees are natively from the tropics and subtropics, so they prefer growing in USDA zones 9-11. However, some varieties can tolerate zones 8.

For best results, keep lemon trees within 32ºF and 90ºF if possible. This mimics their natural tropical environment and makes them less stressed and more able to absorb nutrients and fend off pests and diseases.

It’s helpful to know how lemon trees naturally cool themselves so we can encourage it when needed.

Lemon trees keep themselves cool by sending moisture from their roots to their leaves and through a process called transpiration.

Transpiration is when plants exhale moisture (much like how we do). This is the reason why walking into a dense forest can feel extremely humid.

This becomes a problem when the lemon tree’s climate is too hot and dry. Essentially, its transpiration and root moisture can’t keep up and cool the plant and its leaves.

Hot and dry weather causes leaves to dry, curl, yellow, brown, and drop. It also causes leaves to get yellow spots, especially if the tree is over-watered and develops fungal issues such as greasy spot.

Let’s see some best practices to tap into our lemon tree’s natural cooling mechanisms:

• Compost and mulch – as mentioned above, compost and mulch are two of the most important practices in any garden, especially regarding water retention and soil temperature control.
• Partial shade – Since lemon trees are natively understory plants, they prefer partial shade from the hot afternoon sun. You can create shade by using umbrellas, shade sails, or other plants. The best direction to shade from is the western sun as it’s the hottest. Aim for at least 2 hours of relief.
• Plant Density – To boost transpiration, create as much plant density around your lemon trees. This raises the humidity and provides partial shade to the lemon tree and its soil, significantly cooling it. A good way to do this is with companion planting.

Cold Weather

I grew up in Orlando, Florida, and while lemon trees grew well there, they had trouble growing even 1-2 hours north.

Lemon trees are surprisingly sensitive to frost and get yellow leaves as a result of the stress.

If possible, provide your lemon trees with protection in freezing weather (32ºF, including wind chill).

Here are some tips to help with this:

• Cover the canopy with sheets – Even just a simple bedsheet over your lemon tree reduces the effects of windchill and ice buildup. Combine this with other tips on this list for the best results.
• Insulate trunk and roots – Insulate the trunk with sheets of cardboard and the ground with 4-12 inches of mulch such as leaves, wood chips, or hay. This goes a long way and helps prevent the ground (and roots) from freezing.
• Windbreak – Provide a windbreak if possible. Some ideas are planting along a wall or growing larger, hardier trees near your lemon tree. South-facing walls are best as they retain and reflect heat onto the lemon tree.
• Move potted trees indoors – The best place is next to a southern-facing window (north-facing if you’re in the southern hemisphere). Make sure to keep the tree away from central heat as its leaves will get too dry and drop—this happened to my lemon tree.

Lack of Sunlight

Lemon trees generally require at least 6 hours of sunlight to photosynthesize properly. Without it, their leaves turn yellow and they’re unable to develop sugars for the plant. Over time, this low energy leads to the plant’s declining health, and eventually, the tree can die.

Here are some ways to boost sunlight for your lemon tree.

• Plant the lemon tree in a south-facing direction for maximum sunlight (north-facing if you live in the southern hemisphere)
• Plant the tree along a south-facing wall to reflect more sunlight and heat onto the tree (some heat even persists into the night).
• Prune some overstory trees that are blocking the lemon’s canopy from the sun. You can also prune the lemon tree itself to allow more light to reach the mid and lower branches. This new space also increases aeration from the sun and wind—discouraging disease from spreading.

3. Lack of Nutrients

Nutrient Deficiency	Leaf Symptom
Nitrogen	Entire leaf is pale or yellow
Iron	Dark green veins, rest of the leaf is yellowing
Zinc	Yellow blotches
Manganese	Broadly pale leaves, foliage color looks mottled or smeared

Lemon trees that lack nutrients often get yellow leaves and yellow spots, with the most common deficiencies being nitrogen and iron.

Yellow leaves are often called Chlorosis, which is the lack of production of chlorophyll. Without the green pigment from chlorophyll, the plant has a harder time photosynthesizing and creating the energy (sugars) it needs to survive.

So, what’s the best way to fertilize lemon trees?

Provide lemon trees with either fertilizer or compost. Apply the fertilizer as directed or 2 inches of compost every 1-2 months.

If you’re using fertilizer, the two main options are organic and inorganic (chemical).

While chemical fertilizers are good in the short-term, they often have long-term effects such as drying out the soil and killing off soil life, making it more difficult for the plant to survive.

Alternatively, compost provides more than enough nutrients for plants and builds the soil’s health—bringing other benefits such as increased nutrient uptake, water retention, and erosion prevention.

For this reason, many gardeners are finding that compost is replacing fertilizers.

However, some fertilizers have their place, especially if your soil has poor fertility (just make sure the fertilizer isn’t making the nutrient cycle worse).

For our lemon tree pictured above, it appears that it has an iron deficiency due to the yellow leaves having green veins.

To help fix this, we’re using an organic fertilizer, which should have plenty of iron. To be safe, we’re also supplementing with kelp (high in iron and potassium).

However, while nutrients are essential, a balanced soil pH is needed for proper nutrient uptake.

Imbalanced Soil pH

Lemon trees prefer a soil pH of 6.0-7.0.

As with most plants, lemons prefer a slightly acidic soil pH. This is because an acidic pH is required to dissolve the nutrient solids and make them accessible to the plant’s finer roots.

Fourteen of the seventeen essential plant nutrients are obtained from the soil. Before a nutrient can be used by plants it must be dissolved in the soil solution. Most minerals and nutrients are more soluble or available in acid soils than in neutral or slightly alkaline soils.

Donald Bickelhaupt, SUNY College of Environmental Science and Forestry

The best ways to check your soil’s pH are with pH strips or a meter. I prefer using a pH meter since they’re easy to use and affordable. To see which pH meter I use and recommend, check out my recommended tools page.

If you find your lemon’s soil pH is too acidic (below 6.0), apply alkaline amendments such as wood ash, biochar, or lime.

For soil that’s too alkaline (above 7.0), apply acidic amendments such as sand, peat moss, and coffee grounds.

4. Transplant Shock

If your lemon tree was recently planted or repotted, and its leaves are starting to curl, yellow, or brown, it’s likely due to transplant shock. Transplant shock occurs when a plant is exposed to a new environment and has to establish a new root system.

Avoid transplanting lemon trees unless necessary as it can take up to 1 year for recovery.

To help avoid transplant shock, I like to plant with the following steps in mind:

1. Have the new ground (or pot) prepared
2. Remove as much of the plant’s current topsoil as possible, without damaging the shallow roots
3. Grab the base of the plant’s stem and wiggle lightly
4. Using your other hand, scoop up and support the rootball
5. Lightly place the plant in the new ground (or pot) and fill it in
6. Make sure the soil is at the same level on the plant as before
7. Apply 2 inches of compost and 4-12 inches of mulch to the top of the soil
8. Water generously and add more soil as needed

5. Pests

The most common pest to affect lemon trees are aphids.

Aphids are small bugs that suck the sap from underneath the lemon tree’s leaves. This loss of sugar and moisture causes the leaves to curl, yellow, and drop.

When aphids suck the plant’s sap, they deposit honeydew—which attracts ants. If left unchecked, aphids can damage the plant’s health and potentially stunt or kill it.

These bugs come in multiple colors including white, yellow, or black, and usually are found hiding underneath the leaves. Typically, aphids won’t cause damage to the fruit, but because they suck sap from the plant, they can compromise its health and therefore reduce fruit size and yield.

The best ways to get rid of aphids (and mites) on lemon trees is by spraying the infected leaves with water or neem oil, or releasing ladybugs (a natural predator of aphids and mites). Most often, a jet of water is enough to knock them off and kill them, but neem oil is a good second option.

For example, when my potted Kaffir lime tree had aphids, I found that a jet of water was sufficient to blast them off and prevent them from coming back. All I did was remove the hose nozzle and used my thumb to increase the pressure. Just keep in mind that too strong of a blast can damage the leaves.

Other bugs that cause leaf curl on lemons include:

• Leafhoppers
• Leafrollers
• Whiteflies
• Scale
• Mites

Mites can be managed in the same ways as aphids (water, neem oil, ladybugs).

To learn more about lemon tree pests and how to manage them, check out this resource by the Government of West Australia.

6. Diseases

Root Rot

Root rot, also called Phytophthora Root & Crown Rot, is a root fungus that causes lemon tree leaves, blossoms, and fruit to droop, yellow, brown, and drop. It also causes yellow spots.

This disease typically occurs in areas with poor drainage. To prevent and treat root rot, promote well-draining soils and transplant young trees with fresh soil if necessary. Raised beds are also helpful in improving soil drainage.

There is no chemical control available for crown and root rot in the home garden. The most important control strategy is careful water management.

Clemson University Cooperative Extension Service

My potted Kaffir lime tree had root rot recently, which I was able to tell based on the sopping wet soil and swampy smell. Fortunately, after repotting the tree with fresh potting soil and waiting a few days, the tree made a full recovery!

Greasy Spot Disease

Greasy spot (Mycosphaerella citri) is a fungal disease that causes the underside of lemon tree leaves to get yellow, brown, and black lesions. Soon after, the topside of the leaves will share the same spots. This disease causes lemon tree leaves to drop in the fall and winter.

The spots are a lighter yellow on lemon and grapefruit trees, and darker on tangerine trees. Occasionally, the fruit is affected.

Greasy spot originates from the soil, as spores are released from rain, watering, or dew. The most common time for this is in the warmer months of late spring to early summer (April to July).

Here are some ways to avoid fungal growth on your lemon tree:

• Avoid over-watering
• Prune for airflow and sunlight
• Keep in 6+ hours of daily sunlight

In Florida, greasy spot is usually controlled with a single application of oil or oil and copper in mid-May to June or two spray applications which are timed to be applied in mid-May to June with the second application in late July.

S. H. Futch and L. W. Timmer, Horticultural Sciences Department, UF/IFAS Extension

While copper sprays are generally considered organic, keep in mind they can still be toxic in some conditions.

A Note on Pesticides, Fungicides, and Herbicides

My parents recently had an issue with caterpillars eating their basil plants and they were about FED UP. Every time they’d plant basil plants, the caterpillars ate it.

Fortunately, they found an organic spray at their local nursery that’s made from fermented rum. The day after spraying, they’d find dead caterpillars on the soil.

If you’d like to find out more about this organic spray, you can find it here on Amazon.

So, what’s my point here?

Even though chemical sprays and fertilizers are an easy way out, like all easy and convenient things, there are usually long-term costs. Namely to the plants, soil, and surrounding beneficial life.

Before using chemical sprays, weigh the pros and cons and consider trying organic or permaculture-based treatments first!

To give you a head start, Stefan Sobkowiak – The Permaculture Orchard has a great video on a safe, homemade, and more importantly—effective fungicide (hint: the secret ingredient is whey).

Also, check out how Mark Shepard uses a method called STUN (Sheer-Total-Utter-Neglect) to help his berries, fruit, and nut trees THRIVE.

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