We have a lime tree that recently had some leaves falling off, and we were concerned the tree was dying. So, I did some research and testing to find out more. Here’s what I found.
Lime trees drop their leaves due to stress from water, nutrients, and weather. While lime trees are evergreen and normally keep their leaves year-round, these stressors can cause the tree to drop leaves, even in the summer. For best results, only water when the soil is dry and provide sufficient nutrients.
So, while lime trees commonly drop leaves from several issues, how can we tell which issue is causing it? And how can we fix it? Let’s take a closer look.
1. Over or Under-Watering
Lime leaves can lose their leaves for many reasons, even during the spring and summer such as May, June, and July, but the most common cause is improper watering.
Over and under-watering will quickly stress a lime tree and cause it to drop its leaves, blossoms, and fruit.
Before watering your lime tree, check if it even needs water in the first place. This will help tremendously in preventing over and under-watering.
The best way to water lime trees is to only water when the first 2-4 inches of soil is dry. You can check this by pushing a finger into the soil, under the tree’s canopy. The goal is to have similar moisture to a wrung-out sponge.
While moisture meters can help, they’re not always accurate in predicting soil moisture. Because of this, the best way to check is with the finger test mentioned above.
Lime trees that quickly get dry soil also benefit by applying 2 inches of compost and 4-12 inches of mulch on top of the soil, under the tree’s canopy. When applying, keep these materials at least 3 inches from the tree’s trunk to prevent mold.
This is because compost is amazing at improving the soil’s richness and water retention (source), while mulch dramatically reduces evaporation and protects the soil from the elements.
However, if your lime tree’s soil has been sopping wet for over 1 hour after watering, hold off on water and look towards amending the soil.
Poor Drainage
If you find that your lime tree’s soil has poor drainage, you can amend it by adding 2 inches of both sand and compost to the top of the soil. Over time, these particles will work their way into the soil and break up larger clumps. Again, keep these materials at least 3 inches away from the trunk.
However, if your lime tree’s soil is currently waterlogged, it may be getting root rot soon and will possibly need a more urgent solution. Generally, you can tell if your plant is starting to get root rot by stagnant water and a swampy smell (this is what happened to my potted Kaffir lime tree).
In the case of root rot, both planted and potted lime trees will need to be transplanted with fresh soil to save them. While transplant shock might create more stress for the tree (more on this later), it’s usually necessary to save it.
Along with dropping leaves, over-watering can also cause lime trees to get yellow leaves. If your lime tree has yellow leaves, make sure to check out my other post: How to Fix Yellow Leaves on Your Lime Tree.
2. Lack of Nutrients
If lime trees have insufficient nutrients, their leaves turn yellow or brown before dropping. Generally, lime trees do best with a fertilizer with double the nitrogen to phosphorus and potassium, such as an NPK of 6-3-3.
Alternatively, you can apply 2 inches of quality compost every 1-2 months.
As with most plants, lime trees need sufficient nutrients to function and live properly. Without them, lime trees are more vulnerable to pests, diseases, and poor weather.
Plants require three main nutrients: nitrogen, phosphorus, and potassium (commonly abbreviated as NPK). While lime trees do well with a balanced fertilizer, they prefer one with double the nitrogen.
Higher nitrogen leads to better and more foliage which helps the tree capture more sunlight. In turn, photosynthesis in the leaves creates sugars that help the fruit ripen.
Compost vs Fertilizer
If you’re not a fan of chemical fertilizers, organic compost is just as good, if not better.
While compost may not have the volume of nutrients as chemical fertilizers, compost’s nutrients are typically more absorbable by the tree, especially if it’s fresh and alive with beneficial bacteria. Compost also greatly helps other beneficial soil life, such as mycorrhizal fungi.
As a result, these soil organisms help the tree by gathering nutrients beyond the reach of its roots in exchange for sugars from the tree’s photosynthesis. They also network nearby trees together through the soil, boosting the trees’ pest and disease resistance, as well as the soil’s water retention.
Mycorrhizal fungi promote many aspects of plant life, in particular improved nutrition, better growth, stress tolerance, and disease resistance.
Department of Biology, University of Fribourg, Switzerland
However, if you decide to stick with fertilizers, check out my recent post where I reviewed the top three brands: The Full Guide to Lime Tree Fertilizer and the Top 3 Brands.
While nutrients are essential, they’re not the entire story.
Soil pH
As with most fruit trees, lime trees prefer a soil pH of 6.0-7.0.
Lime trees require a balanced soil pH to properly absorb the nutrients from the soil. Without a balanced soil pH, the nutrients will be inaccessible to the roots, and the tree will die after using up all of its stored nutrients.
Soil that’s either too acidic or too alkaline will bind the nutrients in the soil. This is especially common in soils that have a high clay content.
A good way to check for this is by using pH strips or a pH meter. To see which pH meter I use and recommend, you can visit my recommended tools page.
If you find that your lime tree’s soil pH is too acidic (below 6.0), consider amending it with alkaline materials like biochar, charcoal, and wood ash.
On the other hand, if your lime tree’s soil pH is too alkaline (above 7.0), use acidic amendments such as sand, peat moss, and coffee grounds.
3. Extreme Weather
Lime trees are native to subtropical and tropical climates including USDA hardiness zones 9-11. Because of this, avoid letting your lime tree reach temperatures below 35ºF.
However, some lime tree varieties, and those grafted on more hardy rootstocks, can tolerate colder weather.
For best results, aim to keep lime trees within 50ºF to 100ºF. Any more or less and the tree will expend energy to survive the weather. If this goes on for too long, the stress will cause the tree to become stunted or die.
To help prevent this, here are some tips that can help in either of the two extreme climates:
Hot Weather Tips
Generally, it’s difficult for lime trees to get too hot since they prefer tropical climates. However, if you live in a hot and dry climate, such as California, Arizona, and New Mexico, lime trees need a bit more care.
- Apply 2 inches of compost and 4-12 inches of mulch. These soil amendments are vital in hot and dry climates where soil can dry in a matter of minutes. Reapply compost every 1-2 months and mulch every 3-6 months.
- Shade lime trees from the afternoon sun. The afternoon sun is much hotter than the morning sun, so providing shade from the west of the lime tree is super helpful. You can use umbrellas, shade sails, or other trees (acacia works great and is a nitrogen-fixer).
- Bring potted lime trees indoors during heat waves, and avoid exposing the tree to dramatic temperature swings. If the indoor temperature has a difference of 30ºF or more, move the lime tree gradually if possible.
Cold Weather Tips
- Insulate the tree’s trunk and canopy with cardboard or bedsheets during times of frost. You can also use plastic tarps to reduce ice exposure.
- Build a mound for planted trees. Planted lime trees can benefit from a 1-2 foot high mound of mulch during frost to help insulate them.
- Avoid exposing potted lime trees to central heat. When moving indoors, central heat can do more harm by drying out the leaves quickly. This happened to my potted Meyer lemon tree one winter. After moving it to a cooler room, it made a quick recovery.
4. Transplant Shock
If you’ve recently relocated or repotted your lime tree, and its leaves are drooping or falling off, it’s most likely affected by transplant shock. Lime trees can become stressed from the damage from moving and having to establish a new root system. For best results, avoid damaging the rootball and plant the tree quickly.
Lime trees that get transplant shock will commonly show symptoms such as wilting, yellowing, browning, or dropping leaves, blossoms, and fruit. If severe enough, the tree will die.
Transplant shock can last up to 1 year as the tree attempts to adjust to its new environment and grow new roots.
If you’d like, here are some steps that I commonly use to prevent transplant shock with my fruit trees:
- Have the new ground (or pot) prepared
- Remove as much of the tree’s current topsoil as possible, without damaging the shallow roots
- Grab the base of the tree’s trunk and wiggle lightly
- Using your other hand, scoop up and support the rootball
- Lightly place the tree in the new ground (or pot) and fill it in
- Make sure the soil is at the same level on the trunk as before
- Apply 1-2 inches of compost and mulch to the top of the soil
- Water generously and add more soil as needed
When planting, take care to avoid thorns!
5. Pests and Diseases
Aphids
Aphids are small bugs that suck the sap from underneath the lime tree’s leaves. This loss of sugar and moisture causes the leaves to curl, discolor, and drop. They also deposit honeydew, which attracts ants. If left unchecked, aphids can damage the lime tree’s health and potentially stunt or kill it.
These bugs come in multiple colors including white, yellow, or black, and usually hide underneath the leaves. Typically, aphids won’t cause damage to the fruit, but because they suck sap from the trees, they can compromise its health and therefore reduce fruit yields and size.
The best ways to get rid of aphids on lime trees are by spraying the infected leaves with water or neem oil, or by releasing ladybugs (a natural predator of aphids). Most often, a jet of water is enough to get rid of 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 enough 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. Keep in mind that too strong of a blast will damage the leaves.
Citrus Leaf Miners
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.
Recommended: How to Fix White Leaves on Citrus Trees
Leaf miners are small white moths that lay larvae to burrow inside of 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:
- Fennel
- Caraway
- Dill
- Yarrow
- Parsley
- Tansy
- Zinnia
- Coriander (cilantro)
- Queen Anne’s lace
- Sweet alyssum
Avoid using sprays as they’re not that effective and will cause more damage (instead promoting 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 lime 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.
Root Rot
Root rot (also called Phytophthora Root & Crown Rot) is a root fungus that causes leaves, blossoms, and fruit to droop, yellow, brown, and drop.
This disease typically occurs in soil with poor drainage. To prevent and treat root rot, promote well-draining soils and transplant the lime tree with fresh soil if necessary.
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
As mentioned earlier, my potted Kaffir lime tree had root rot at one point and it made a full recovery after I repotted it with fresh potting soil. So, if your lime tree’s soil is sopping wet days after watering it, and it’s starting to smell like a swamp, repotting will likely fix it!
How Do You Revive a Dying Lime Tree?
You can revive a dying lime tree by first checking its water, drainage, and then nutrients. After, inspect the leaves for any signs of pests or disease such as spots or holes.
If your lime tree is continuing to shed its leaves and decline in health, and you’d like some more assistance, I recently wrote a post you may find helpful: 3 Quick Steps To Revive a Dying Citrus Tree.
