We have several fruit trees, and while they all do fairly well, our potted Meyer lemon recently had some fruit that was yellowing and falling off. While some flower and fruit drop is normal, I was worried that we would have little to no lemons this year. So, I did some research to find out more. Here’s what I found about why citrus trees drop fruit.
It’s normal for citrus trees to drop up to 98% of their potential fruit. If citrus trees held onto all of their blossoms and buds, the tree wouldn’t have enough water and nutrients to go around. Other causes of fruit drop include improper watering, a lack of nutrients, poor pollination, and extreme weather.
So, while it’s normal for citrus trees to lose most of their fruit, why is this the case, and can we do anything to increase our tree’s fruit yields?
Citrus trees naturally lose up to 98% of their total fruit. This is normal behavior and helps make sure the citrus tree is not overburdened. If a citrus tree grew 100% of its fruits, the lack of nutrients and water would mean they’d be the size of a coin and none of them would be fully developed.
This fruit drop event is so common, that it even has a name—June drop. While most of the fruit is lost when they’re buds, some of the more developed fruit is lost in June (when they’re 1/2 to 1 inch in size). Even more fruits are sometimes lost in the winter.
Fruits are how citrus trees reproduce, and it might help to think of their reproduction like other life on this planet. For example, if you’ve seen Finding Nemo, you’d know that fish lay millions of eggs, yet 99% of fish eggs don’t reach maturity.
So, while it can be disappointing to not see all of the flowers and buds become fruits on your citrus tree, know that natural fruit (and blossom) thinning is a normal way for citrus trees to focus their energy on the strongest fruits to ensure their genetic survival.
To simulate this, some citrus growers even prune some of the tree’s flowers to help redirect its energy to a fewer selection of flowers, ensuring the chance they’ll become pollinated and develop into fruit (more on pollination later). While this has often been shown to work, it’s not necessary if you provide well for the tree.
But, what if your citrus tree is losing nearly all (or all) of its budding fruit? That can’t be normal right?
Let’s take a look at the other factors that can lead to fruit drop and see what we can do to maximize fruit yields of the 2% of the fruit that’s remaining.
Over or Under-Watering
Over or under-watering citrus trees can stress them, and as a result—they drop their remaining fruit. The best way to water citrus trees and prevent fruit drop is to only water when the top 2-4 inches of soil gets dry. Also, providing compost and mulch increases the nutrients and water, helping the tree retain fruit.
“It has been shown, that water stress during the late spring/early summer can cause a yield reduction, otherwise known as June drop (although some drop is normal). Once we get past that period, trees can tolerate substantial water stress without crop loss. However, what will happen if we don’t apply adequate water, will be a significant reduction in fruit size. June is critical for fruit drop(yield reduction), and July-Oct is critical for size reduction.”Nick Sakovich, Professor at University of California
- Overwatering citrus trees drown their roots, potentially leading to root rot (a fungal disease)
- Under-watering citrus trees lead to drought stress, and the tree conserving moisture for itself (and not its fruit)
Both over and under-watering citrus trees create a stressful situation where the tree needs to make a judgment call to survive. For the tree to conserve enough nutrients and water to survive, it must shed its fruit (in addition to buds and leaves).
While it can be tricky to find out how much water citrus trees need, a good rule is to only water when the top 2-4 inches of soil gets dry.
If you live in a hotter climate, you might be thinking that this means watering your trees daily. Fortunately, some practices decrease your citrus tree’s water needs and help them become more self-sufficient. This in turn increases their fruit yields! Let’s take a look at these best practices.
Composting the soil around the drip line of citrus trees not only provides them with amazing nutrients but also improves the richness of the soil. It’s shown that with each 1% increase in a soil’s organic matter, the soil can hold 20,000 gallons more water per acre.
Mulching the soil protects the tree’s roots and beneficial soil life from overheating and drying in the sun. Keeping the citrus tree’s roots cool and moist is important because, in times of heat, the roots send moisture to cool the rest of the tree—including its branches, leaves, and fruit. On the other hand, the mulch protects the soil life, helping them thrive and continue providing nutrients to the tree’s roots (in exchange for sugar).
Also, checking the soil’s drainage is important when watering citrus trees.
My potted Kaffir lime had poor soil drainage at one point, which led to overwatering it. I found out when the soil started smelling swampy. I dug down to feel the lower soil, and sure enough, it was sopping wet, even after not watering it for days. Fortunately, repotting it was all it needed to overcome the root rot.
So, to recap:
- Make sure the soil is well-draining
- Only water when the top 2-4 inches of soil gets dry
- Provide 1-2 inches of compost 1-2 times per month (this can also replace fertilizer)
- Provide 1-2 inches of mulch every 3-6 months (leaves, pine needles, or straw work nicely)
A large swing or extreme temperatures can also lead to citrus tree fruit drop. With these events, the citrus tree becomes stressed and conserves its resources to ensure the tree’s survival. As a result, it often sheds the less vital parts of the tree—its leaves, buds, and fruit.
Citrus trees grow best in temperatures between 35-100ºF, but 60-80ºF is the sweet spot. Native to the tropics, citrus trees like warm weather and medium to high humidity.
If the weather takes a swing of 30ºF or more, or gets too hot or cold, the citrus tree begins to go into a state of dormancy to survive. During this time, the tree commonly redirects resources to its trunk and sheds its leaves, buds, and fruit. If this extreme weather continues, the tree will likely die.
So, what can we do to help our citrus trees survive extreme weather?
To keep your citrus trees cool in the summer, use compost and mulch and provide them with 2 hours of shade during the hottest part of the day. This is typically around 2-4pm.
While composting and mulching citrus trees is a good practice to keep them cool in hotter weather, it can be a bit tougher to keep them warm if you live in areas that get moderate to heavy frost.
To keep your citrus trees warm in the winter, insulate them with sheets or cardboard, and provide a windbreak to prevent the effects of wind chill. Additionally, planting them in a south-facing direction will maximize their hours of sunlight and warmth. You can also plant them next to a southern-facing wall to reflect more heat onto the tree, even into the night.
If you have potted citrus trees, an easy way to avoid extreme weather is to simply bring them indoors. For example, our potted Meyer lemon was completely iced over this past winter. Its frozen leaves started to turn a darker color. Luckily, we caught it in time and brought it inside (it’s now summertime, and it’s now bearing lots of fruit!).
Just make sure to keep your potted citrus trees away from the central heat. In our experience, the dry air was killing the tree and the leaves were falling off.
Lack of Nutrients
A lack of nutrients can mean that the citrus fruit will have a hard time developing, eventually leading them to fall off. This can result in little to no fruit on the tree. For best results, give your citrus trees a high nitrogen fertilizer once per growing season, or a quality compost 1-2 times every 1-2 months.
When citrus trees aren’t able to provide enough water and nutrients for their fruit, the fruits become weak and prone to pests and disease. This entry point for pests and diseases can also infect the rest of the tree. To help ensure its survival, citrus trees typically choose to drop these fruits.
Keep in mind that sufficient nutrients in the soil aren’t the only thing citrus trees need. Citrus trees also need an appropriate soil pH, preferably 6.0-7.0. If the soil pH falls outside of this range, the tree will have a hard time absorbing nutrients from the soil.
If you’d like more information about which citrus tree fertilizers I use, you can check out my recommended citrus fertilizer page.
Alternatively, if you’d like to make your own citrus tree fertilizer at home, you might like my recent post: Craft the Perfect Homemade Fertilizer for Your Citrus Tree.
Lack of Pollination
|Cross-Pollinating Citrus||Self-Pollinating Citrus|
|Mandarin Oranges||Navel Oranges|
While most citrus trees are self-pollinating and don’t require another citrus tree to produce fruit, they can still benefit from cross-pollination. Cross-pollination helps to ensure the blossoms will become fertilized and can lead to increased fruit yields and size. This results in fewer buds and fruit dropping.
You can increase your citrus tree’s pollination by planting pollinator-friendly flowers and other companion plants for citrus trees.
Common pollinators for citrus trees include bees, butterflies, hummingbirds, and the wind. You can also pollinate by hand by using a toothbrush, paintbrush, or q-tip and lightly brushing from flower to flower (which can be super helpful for indoor citrus trees).
For more information about the pollination of citrus trees, you can check out my recent post: Do Citrus Trees Cross-Pollinate or Self-Pollinate?.