Our lemon tree was getting some white leaves that would curl and drop from the tree. In my search for answers, I saw there are several reasons why citrus trees get white leaves. So, I put together this guide to help simplify things and get you a quick solution. Here’s what I found.
Citrus trees get white leaves from over-watering, improper sunlight, a lack of nutrients, and pests such as spider mites and leaf miners. Ideally, only water when the soil is dry. Provide 6+ hours of sunlight and a 6-3-3 NPK fertilizer or compost. Use neem oil or traps for mites and leaf miners.
So, how can we tell which issue is causing the white leaves, and how can we fix it? Let’s take a closer look.
Citrus trees prefer moist, but not wet soil. If the soil is compacted or high in clay, it won’t drain well, which leads to waterlogged soil.
Waterlogged soil begins to drown the citrus tree’s roots, causing issues such as yellow leaves, white leaves, dropping leaves, and root rot.
Fortunately, there’s an easy way to water citrus trees to prevent both under and over-watering.
Only water citrus trees when the first 2-4 inches of soil gets dry. I check this by pushing a finger into the soil. When watering, soak the soil down to 2 feet deep as 90% of the tree’s roots are found within this depth.
But what happens if your soil doesn’t have proper drainage in the first place? How can we quickly test and amend it?
To measure your soil’s drainage, consider doing a percolation test.
Here’s how to do one:
- Dig a 1-foot by 1-foot hole
- Put a yardstick in it and fill it with water
- 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 water in the holes 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 way off. This test is primarily to determine if your soil drainage is excessively too fast or slow.
How to Fix Soil 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)|
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 citrus 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 your citrus trees (more on fertilizers later).
2. Improper Sunlight
Since citrus trees are natively from the tropics and subtropics, they require 6+ hours of sunlight a day.
Without proper sunlight, 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 citrus tree.
- Plant your citrus 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 citrus tree’s canopy from the sun. You can also prune the citrus tree itself to allow more light to reach its mid and lower branches. This new space also increases aeration from the sun and wind—discouraging disease from spreading.
Alternatively, too much sunlight and heat burns or dries out citrus trees.
In this case, the tree’s leaves begin to dry, curl, brown, and drop. It’s important to keep an eye on the citrus tree’s soil moisture as it’s the primary way they stay cool.
3. Lack of Nutrients
Sometimes a lack of nutrients causes citrus tree leaves to become pale yellow, and even white if the deficiency is bad enough or persists for a long time.
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.
The most likely deficiencies for citrus trees are nitrogen and iron.
Here’s a table of the most common citrus tree deficiencies and how you can identify them.
|Nutrient Deficiency||Leaf Symptom|
|Nitrogen||Entire leaf is pale or yellow|
|Iron||Dark green veins, rest of the leaf is yellowing|
|Manganese||Broadly pale leaves, foliage color looks mottled or smeared|
So, what’s the best fertilizer for citrus trees?
Provide citrus trees with a quality 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 its yellow leaves having green veins.
While nutrients are essential, a balanced soil pH is needed for proper nutrient uptake.
Imbalanced Soil pH
Citrus trees prefer a soil pH of 6.0-7.0.
As with most plants, citrus trees 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 citrus tree’s soil 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. Spider Mites
You can tell if your citrus tree has spider mites if you see small dots running around on the tree’s leaves. Spider mite colors range from red, brown, yellow, and green.
Common symptoms of spider mites on citrus trees are leaves yellowing, paling, and dropping. Fruit dropping is also common as the mites weaken the tree.
Like aphids, mites can be sprayed with water or neem oil (this worked to remove aphids from my Kaffir lime tree).
Some ways to prevent both mites and thrips are to encourage their natural predators:
- Green lacewing
- Beneficial wasps
To attract the above beneficial insects (and make your job easier), avoid dust, pesticides, and select diverse companion plants. If your citrus tree’s leaves get dusty, give their leaves a quick rinse.
5. Citrus Leaf Miner
We recently purchased a young lemon tree from our local nursery, and it soon started to get leaves that curled and dropped. The leaves also had some bumps and white trails. We sent it off to be analyzed and they told us it was leaf miners.
Leaf miners are small white moths that lay larvae to burrow inside the leaves of citrus trees, causing them to curl and drop. This pest is fairly common in most of California along with Florida and Mexico.
The good news is that leaf minors don’t cause much damage and are only a concern for young citrus trees. Once the leaves harden off and mature, the leaf miners won’t be able to penetrate them.
The best way to prevent and manage leaf miners is to encourage natural predators such as beneficial wasps (the non-stinging kind).
You can do this by planting companion plants such as:
- Coriander (cilantro)
- Queen Anne’s lace
- Sweet alyssum
Avoid using sprays as they’re not that effective and will cause more damage (they’ll promote whiteflies, scale insects, and other citrus pests).
Available insecticides for backyard trees are not very effective and many products leave residues that kill natural enemies, compounding problems.University of California Agriculture & Natural Resources
Also, avoid pruning leaves infected with leaf miners as the leaves are still functional and feeding the citrus tree via photosynthesis. Pruning can cause more damage in this case.
Feel free to prune leaves that are brown as they’re no longer assisting with photosynthesis, but it’s not necessary.
For our lemon tree, here’s the trap we used to get rid of our leaf miners.
6. Powdery Mildew
Powdery mildew is a fungal disease that appears as small white spots (spores) on the citrus tree’s leaves. It causes citrus tree leaves and twigs to curl and die, as well as leaves and fruit to drop.
This issue is made worse in areas with high humidity and poor ventilation.
For example, if your citrus tree’s canopy is thick, it’ll have reduced airflow and sunlight—promoting fungal diseases such as powdery mildew.
You can control or prevent powdery mildew by pruning to improve ventilation and sunlight and using a spray (I recommend saving this as a last resort).
To start, prune overlapping or clustered branches. Pruning a citrus tree’s canopy also trains it to spend less energy on foliage and more on fruiting (great for mature citrus trees). It also allows it to grow more fruit on fewer branches.
Avoid over-pruning as it weakens the tree and can make its recovery harder.
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.