We have a lime tree in our backyard and to be honest, it’s not doing so well. It was recently over-pruned and most of its fruits are falling off well before ripening (sizes ranging from marbles to golfballs). To help fix it, I did some research. Here’s what I found.
It’s normal for citrus trees to drop the majority of their fruit in May, June, and July due to a natural shedding event called June Drop. However, if the trees are dropping fruit other times of the year, it’s caused by improper watering, climate, nutrients, pollination, and occasionally—pests and diseases.
So, while several causes lead to fruit drop on citrus trees, how can we tell which issue is causing it, and from there—how can we fix it? Let’s take a closer look.
Citrus trees that are under-watered experience symptoms such as fruits dropping and leaves drooping, curling, browning, and dropping. When stressed, citrus trees choose to keep their leaves alive over their fruit as leaves are vital for photosynthesis and feeding the tree.
Since citrus trees are from the tropics, they do best in hot climates and sandy soils. However, due to the heat, and the quick drainage from the sand, citrus tree soil often dries out quickly.
As a result, proper watering practices are essential to keep citrus trees healthy and fruiting.
The best way to water citrus trees is to only water when the top 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 should be soil moisture similar to a wrung-out sponge.
When watering, make sure to soak the soil at least 2 feet deep as over 90% of the citrus tree’s roots are found at this depth.
Additionally, apply compost and mulch under your citrus tree’s drip-line to greatly boost the soil’s water retention.
Compost not only provides valuable nutrients but increases the soil’s richness. Every 1% increase in the soil’s richness or organic matter leads to an additional 20,000 gallons of water held (source).
Mulch is fantastic at reducing evaporation, regulating soil temperature, and preventing erosion of topsoil. Citrus trees evolved as understory trees in forests, so they prefer tons of mulch (in the form of branches and leaves) and partial shade from the hot afternoon sun.
Apply 2 inches of compost and 4-12 inches of mulch under your citrus tree’s canopy.
Keep these materials at least 3 inches from the trunk to avoid mold buildup. Reapply compost every 1-2 months and mulch every 3-6 months.
However, a lack of water isn’t the only thing that stresses citrus trees to drop their fruit.
Over-watered citrus trees develop symptoms including fruit drop as well as leaves drooping, yellowing, and dropping.
Providing too much water isn’t likely to occur if you’re following the above guideline of only watering when the first 2-4 inches of soil is dry.
However, it’s most common in soils that have poor drainage.
You can tell if your soil has poor drainage by doing a percolation test. To do this, dig a 1-foot by 1-foot hole nearby and fill it with water. Ideally, the water should drain around 2 inches per hour. Make the hole outside of your citrus tree’s drip-line (canopy) to avoid damaging the tree’s shallow roots.
Keep in mind the 2 inches per hour is a guideline and not a rule, so don’t stress if it’s not draining exactly at this rate.
If you find your soil has fast drainage (well above 2 inches per hour), apply 2 inches of compost every 1-2 months and 4-12 inches of mulch. The organic matter will work its way into the soil, amending the soil and helping it hold more water.
Interestingly enough, the solution is the same for soils with poor drainage (well below 2 inches per hour)—apply 2 inches of compost every 1-2 months. This is because organic matter both breaks up compact soils as well as maintains the proper water retention.
However, avoid mulching in poorly draining soils as it can limit evaporation and make them worse. Provide your citrus tree with mulch once its soil is well-draining.
3. Extreme Weather
Citrus trees are natively from the tropics and subtropics and do best in USDA hardiness zones 9-11. As a result, keep your citrus tree within temperatures between 32ºF and 90ºF for optimal growth and fruiting.
When citrus trees get hotter or colder than this or have sudden temperature swings (usually of 20ºF or more), they become stressed and drop their fruit. If it’s bad enough, they’ll also drop their leaves.
While it can be difficult to manage a citrus tree’s temperature (especially if they’re planted outside), there are some tips and tricks you can do to help.
Tips for Hot Weather
Citrus trees primarily cool themselves by sending moisture from their roots to their leaves, and by a process called transpiration.
If you’ve ever walked through a dense forest and felt the humidity increase, it’s because of the plants. Similar to how we release moisture when we exhale, trees do the same and it’s called transpiration.
So while the top side of the leaves are similar to a solar panel and collects sunlight, the underside of the leaves is used to breathe and release moisture to help keep the plant cool.
However, when the weather gets too hot, the tree’s root moisture and transpiration can’t keep up, and the tree’s fruit and leaves pay the price.
Here’s what you can do to help keep your citrus trees cool (ideally in temperatures 90ºF and above).
- Compost and mulch are two of the best practices in caring for citrus trees. The water retention and temperature regulation they bring do wonders to keeping citrus trees cool (meaning you can water less). 2 inches of compost and 4-12 inches of mulch work best.
- Provide partial shade from the afternoon sun. The afternoon sun is much hotter than the morning sun and giving your citrus trees partial shade goes a long way. Since citrus trees evolved as an understory plant, they’re used to having a bit of shade cover from the canopies of larger trees.
A good way to provide your citrus trees with both nutrients and shade is by using larger, support trees. These are also called pioneer species (the first species to grow in disturbed landscapes) and are typically nitrogen-fixing.
For example, we have acacia trees growing in our backyard, giving our citrus trees both partial shade and nitrogen in the soil.
Tips for Cold Weather
It’s not as common to grow citrus trees in colder climates (for good reason), so I won’t go into too much detail here.
Here are the best tips that I’ve found for growing citrus trees in climates with minor frost.
- Plant your citrus tree on the south side of your property (if you live in the southern hemisphere, plant north instead). The south gets the most sun exposure and warmth, so it greatly helps to keep your citrus tree warm. You can also plant along a south-facing wall to reflect more light and heat onto the plant.
- Cover your citrus tree’s canopy sheets or a tarp during frost to reduce windchill and ice buildup.
- Move potted citrus trees indoors when temperatures begin falling below 32ºF. Avoid placing them near the central heat as it will dry their leaves (this happened to my potted Meyer lemon tree).
4. Excess Nutrients
Excess nutrients cause citrus trees to drop fruit for 2 primary reasons:
- Stress from potent chemical fertilizers burning the tree’s roots
- High amounts of nitrogen encouraging foliage growth over fruit growth
Note: Both issues occur from chemical fertilizers as compost isn’t potent enough.
Other symptoms of excess nutrients are yellowing and dropping leaves. If it’s bad enough, the entire citrus tree dies.
Like all plants, the primary nutrients for citrus trees are nitrogen, phosphorus, and potassium (NPK). Generally, nitrogen encourages foliage growth, phosphorus assists flowering and fruiting, and potassium supports healthy cell functions (important for every aspect of the plant).
However, secondary nutrients are also important, such as iron, magnesium, and zinc. Generally, most fertilizers and composts have sufficient primary and secondary nutrients.
The best way to fertilize citrus trees is to apply 2 inches of compost and 4-12 inches of mulch under the tree’s drip-line.
Gardeners are finding out that compost is replacing fertilizers for them, while the mulch breaks down into even more nutrients.
Not to mention the healthy soil life (such as earthworms and mycorrhizal fungi) bringing bonus benefits such as increased water retention, disease resistance, and pest deterrence.
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
So, by using compost and mulch, you’re not only adding many benefits but avoiding the risk of over-fertilizing and causing fruit drop.
However, if you prefer to use fertilizers, check out my recommended fertilizer page.
Keep in mind that nutrients aren’t the entire picture.
Without a balanced soil pH, citrus trees are unable to properly absorb nutrients from the soil. The reason why most plants require a slightly acidic pH is that it dissolves the nutrient solids in the soil.
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, Instructional Support Specialist, Department of Forest and Natural Resources Management
The ideal pH for citrus trees is between 6.0 and 7.0.
To measure your soil’s pH, I recommend using pH strips or a meter. I prefer using a meter since they’re affordable and easy to use. 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 (under 6.0), provide alkaline amendments such as wood ash, charcoal, or lime. On the other hand, for alkaline soil (above 7.0), provide acidic amendments including sand, peat moss, and coffee grounds.
5. Lack of Pollination
Citrus trees that don’t have sufficient pollination often get little to no fruits or fruit drop. Flowers need to be pollinated (fertilized) to turn into fruit. If they’re not, the tree will give little fruit yield.
While self-pollinating citrus trees can fruit, they do best if they’re cross-pollinated.
Although it has been suggested that cross pollination on Washington Navels is not required to increase yield, there is evidence to show that pollination by bees may contribute to less fruit drop.Malcolm T. Sanford, University of Florida
Do You Need 2 Citrus Trees to Get Fruit?
Citrus trees do best when cross-pollinated, so having 2 or more trees is ideal. However, if your citrus tree is self-pollinating, you don’t need a second tree.
If cross-pollinating, ensure you’re pollinating trees of the same variety to maintain the same variety of fruit (unless you’d like hybrid fruits).
Tips to Improve Citrus Tree Pollination
- Keep another citrus tree of the same variety nearby. Ideally, within 25 feet, and no more than 50 feet. Any more than 50 feet and pollinators have a reduced likelihood of visiting both citrus trees.
- Plant companion plants (especially those that flower) within 50 feet of your citrus tree. They’ll attract more pollinators including butterflies, bees, and hummingbirds. Check out these citrus companion plants for starters.
- Manually brush your citrus tree’s flowers to induce fertilization. Use a new and clean q-tip, paintbrush, or toothbrush. This is especially helpful for indoor and potted citrus trees as they’ll likely have limited access to pollinators.
- Start beekeeping to provide a large boost of available pollinators.
Aphids are small bugs that suck the sap from underneath the citrus 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 citrus tree’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.
The best ways to get rid of aphids and mites on citrus trees is by spraying the infected leaves with water or neem oil, or by releasing ladybugs (a natural predator of aphids and mites). Most often, a jet of water is enough to get rid of them, but neem oil is a good second option.
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.
Other pests that cause reduced fruit and fruit drop are mites, thrips, and gophers (which damage the tree’s roots, stressing the tree).
Root rot, or Phytophthora root and crown rot, are fungus-like water molds that affect most, if not all fruiting plants. Causes of root rot are typically over-watering or soils with poor drainage. Symptoms include stunting and leaves wilting, drooping, discoloring, and dropping.
You can typically tell if your citrus tree has root rot if the soil is staying sopping wet and starts smelling. As mentioned earlier, allowing the soil to dry out or repotting citrus trees with new potting soil are the best ways to amend this disease (source).
Verticillium wilt is a fungus that is similar to root rot in that it usually occurs in soils with excess water. Additionally, over-fertilizing can also cause it.
The most susceptible fruit crops that contract verticillium wilt are nightshade (tomatoes, peppers, and eggplants), but other fruiting plants including citrus trees can also be infected. Symptoms of this disease include fruits dropping as well as leaves wilting, yellowing, dropping, and potentially—branch dieback.
You can prevent and treat verticillium wilt by pruning infected branches, avoiding excess water and fertilizers, and following best gardening practices.
It’s completely normal for citrus trees to drop most of their fruits in May, June, and July (AKA “June Drop”). This is a natural shedding that helps the tree not become over-burdened with fruit.
With too much fruit, the tree might not have enough water or nutrients to develop enough of them. Additionally, its branches could break under the weight.
Another reason could be from alternate (biennial) bearing, which is when a tree over-produces one year and has to make up for it the following year.
Over-pruning is another cause as the tree might not have enough leaves to properly photosynthesis or support structure to bear fruit (this is what happened to our lime tree).
However, the improper gardening practices mentioned above have a large impact on fruit drop and normally can be amended quickly.
Need More Help?
You can always ask us here at Couch to Homestead, but you should know the other resources available to you! Here are the resources we recommend.
- Local Cooperative Extension Services: While we do our best with these articles, sometimes knowledge from a local expert is needed! The USDA partnered with Universities to create these free agriculture extension services. Check out this list to see your local services.
- Permaculture Consultation: Need help with a bigger project? Send us a message.