We have several citrus trees including two lemon trees, two lime trees, one tangerine, and one orange tree, and we occasionally see split fruit. While not too many fruits are affected, we wanted to see if there’s anything we can do to solve it. Here’s what we found.
According to the Agriculture Department of Western Australia, citrus fruit splits due to poor nutrients combined with sudden changes in watering and temperature. For example, potassium and calcium deficiencies weaken rinds, and a change in temperature and watering quickly expands the shrunken fruit, leading to cracks.
So, while citrus fruit happens due to a combination of issues, how can we tell which issue is causing it, and from there—how can we fix it? Let’s take a closer look.
1. Lack of Nutrients
Here’s a step-by-step breakdown of why citrus fruits split:
- Potassium and calcium deficiencies create weak rinds
- Insufficient water and hot weather shrink the fruit
- Sudden heavy watering quickly expands the fruit, straining the rind
- The weakened rind can’t handle the pressure and splits
Citrus fruits usually begin splitting in the early summer, but the majority occurs in the autumn. This is likely due to the tree’s nutrient demands during spring, followed by the changing of the weather in the summer and fall.
While many varieties of citrus fruit can split, the most vulnerable are navel oranges, tangelos, mandarins, and Meyer lemons.
Citrus trees are heavy feeders and evergreen (keeping their leaves year-round), so they require plenty of nutrients to grow and develop strong rinds. Nutrients in the soil can be reduced if the citrus tree has:
- Soil that’s too sandy
- Too much water
- Insufficient nutrients from the start
- Too much fruit (more on this later)
For example, sandy soils can have too much drainage, causing nutrients to sink too far into the soil. Watering too much also leaches the nutrients down into the soil. Lastly, if the soil is lacking nutrients, the citrus fruit can’t develop properly, leading to weak rinds.
So, how do we ensure that our citrus tree’s soil has sufficient nutrients to grow and fruit properly?
The Best Fertilizer for Citrus Trees
The three primary nutrients plants require are nitrogen, phosphorus, and potassium (abbreviated as NPK). Secondary nutrients are also important such as iron, copper, and magnesium. However, when it comes to avoiding split fruit, potassium and calcium are the most important nutrients.
The majority of citrus tree fertilizers contain potassium as well as secondary nutrients such as calcium, but if you’re seeing a lot of split fruits, I recommend giving your citrus trees an extra feeding.
To fix split fruit, I recommend feeding your citrus tree an organic fertilizer followed by a potassium and calcium supplement. For example, I use Down to Earth’s Citrus Mix and add kelp (potassium) as well as crushed eggshells (calcium).
Tip: Unlike other fruit trees, citrus and avocado trees require double the nitrogen to phosphorus and potassium. As a result, look for fertilizers that have a 2:1:1 ratio, such as a 6-3-3 NPK.
To see which citrus tree fertilizers I use and recommend, see my recommended fertilizer page.
If you’d like to see more about how to use kitchen scraps to make citrus tree fertilizer, check out my other post: Craft the Perfect Homemade Fertilizer for Your Citrus Tree.
When To Fertilize Citrus Trees
According to Down to Earth and The University of Arizona Cooperative Extension, citrus trees should be fertilized 3 times per year:
- Jan/Feb
- Apr/May
- Sep/Oct
Because citrus trees are evergreen (keeping their leaves year-round) and commonly fruit 1-2 times per year, they typically require more frequent fertilizer application than cold-climate fruit trees. As most temperate fruit trees go dormant during the winter, they don’t require nutrients at that time.
Imbalanced Soil pH
Citrus trees do best with a soil pH of 6.0 to 7.0
While nutrients are important, they’re next to useless if the soil does not have a proper pH. This is because a slightly acidic pH is necessary to dissolve the nutrient solids in the soil and make them accessible for 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, Instructional Support Specialist, Department of Forest and Natural Resources Management
Two good ways to check your soil’s pH are either by using a pH strip or a pH meter. I prefer using a pH 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 that your citrus tree’s soil is too alkaline (above 7.0) you can add acidic amendments such as coffee grounds, sand, and peat moss. On the other hand, if your citrus tree’s soil is too acidic (below 6.0), add alkaline materials such as wood ash, charcoal, or lime (ground limestone).
Additionally, cold and/or wet soils are not good at promoting nutrient uptake as the citrus tree will either be dormant during the cold or too stressed in wet soils.
2. Under-Watered
Under-watered citrus trees are especially vulnerable to splitting as their fruit (and rinds) shrink and become rigid from the lack of moisture. Then, when the tree receives a sudden and large volume of water, it overcompensates—sending the water quickly to the fruit, causing it to expand too quickly.
Because of this, the best way to prevent split fruit is to provide citrus trees with consistent soil moisture. This helps the fruit not dry or shrink and reduces the chance of splitting.
You can typically tell if your citrus tree is under-watered if you see:
- Curled Leaves
- Dry Leaves
- Brown Leaves
- Dropping Leaves
- Bone Dry Soil
So, how do we water citrus trees to prevent splitting (and other issues)?
When & How Much to Water Citrus Trees
The best way to water citrus trees is to only water when the top 2-4 inches of soil gets dry. I check this with the “Finger Test”. Simply push a finger into the soil, under the tree’s canopy. If the soil is dry, water it. If it’s wet, hold off until it’s dry.
By checking your citrus tree’s soil before watering, you’re avoiding both under and over-watering.
The goal is to have soil moisture similar to a wrung-out sponge.
When watering, make sure to water down to 2 feet deep. This is because 90% of the tree’s roots are found at this depth.
Compost & Mulch
If you find your citrus tree’s soil is drying out in a matter of days or hours, you likely need to amend it for better water retention.
Apply 2 inches of compost every 1-2 months and 4 inches of mulch every 3-6 months.
Good mulches for citrus trees include leaves, bark, pine needles, and straw. Apply both materials under the tree’s canopy and keep it at least 3 inches from the tree’s trunk to prevent mold.
Compost not only provides essential nutrients but increases the soil’s water retention and beneficial soil life. For every 1% increase in organic matter (compost), the soil holds an additional 20,000 gallons of water per acre.
Mulch dramatically reduces evaporation, regulates soil temperature, and prevents soil erosion. It also breaks down into nutrients for the tree and prevents weed growth. Since citrus trees evolved as understory plants in forests, they’re used to having plenty of decaying branches and leaves.
However, properly watering your citrus tree might not be enough to stop its fruit from splitting.
3. Extreme Temperature Swings
After being weakened from nutrient deficiencies, and shrunken from a lack of water, citrus fruit can easily split from extreme temperature swings.
For example, if you have cold nights and hot days, your citrus tree’s fruit shrinks at night and quickly expands during the day. This is similar to putting a cold glass dish in the oven. The heat expands it too quickly and can cause it to weaken or crack.
You might be thinking, “What can I do? I can’t control the weather!”.
And that’s true, but the good news is that citrus trees are fairly self-regulating—as long as they have proper moisture in the soil.
So, here’s a recap of the best way to water citrus trees as well as manage their temperature:
- Water when the top 2-4 inches of soil is dry
- Apply 2 inches of compost every 1-2 months for water retention
- Apply 4 inches of mulch for reduced evaporation and temperature regulation
- Establish a microclimate. For example, increase humidity to better protect the tree against temperature swings
For example, you can increase your citrus tree’s humidity by using a humidifier for indoor trees or planting outdoor citrus trees among other plants.
This is because, like us, plants exhale moisture when hot (transpiration).
And if there are enough plants, this can significantly boost the humidity in the area. This is why forests and jungles can be extremely humid and rain more often.
Also, if you find your citrus tree is getting too hot (95ºF), you can provide it with around 2 hours of afternoon shade (from the western sun).
To learn more about microclimates, check out this cool video by Gardener Scott.
4. Not Pruning Fruit
When citrus trees have too many fruits, sometimes there aren’t enough nutrients to go around and develop the fruit properly. This is especially true if the soil is lacking nutrients (such as potassium and calcium). The result is each fruit has a bit less rind.
While you can likely fix this by providing the citrus tree with fertilizer, you can also manage it by pruning some of the excess fruit from the tree.
Don’t worry, mature citrus trees often produce many hundreds of fruits, so pruning a few of them to help other fruits grow better, bigger, and juicier isn’t a bad trade-off.
| Age of Citrus Tree | Amount of Fruit |
|---|---|
| 3 Years Old | 38 lbs (~152 fruits) |
| 4-5 Years Old | over 100 lbs (~400 fruits) |
| 5+ Years Old | 100-200 lbs (~400-800 fruits) |
As for how much fruit to prune, start by reducing 10% of the fruit load. If the fruit continues to split, make sure you’re providing enough water and nutrients. If it continues, continue pruning another 10% of the fruit.
Can You Eat Split Citrus Fruit?
Split citrus fruit can be eaten, but it’s not recommended. The rind is what protects the citrus fruit, and once split, the fruit is exposed to bugs and disease. It’s best to prune the split fruit from the tree and dispose of it so it doesn’t attract fruit flies or citrus disease.
Final Thoughts
After looking at the likely causes, we found our citrus tree needed to be watered more regularly. So, we watered whenever the top of the soil got dry and applied more compost and mulch.
We’ve noticed much less fruit splitting, so it looks like it’s working for now.
Remember, fruit splitting typically starts from potassium and calcium deficiencies and is made worse by sudden watering or extreme swings in temperatures.
For best results, use organic fertilizer, supplement with compost, kelp, and eggshells (or oyster shells), and prune 10% to 20% of the total fruit to promote stronger and bigger fruits.
