My parents have a large orange tree in their backyard, and there was a time when its leaves were turning yellow. Unsure of what to do, we tried searching for the answer online. However, there really wasn’t a good answer out there, so we decided to do some research and test it ourselves. So, why do orange tree leaves turn yellow?
The most common reason why orange trees develop yellow leaves is due to over-watering or a lack of nutrients. Less common causes can be stress, pests, and disease. The best approach to take is to use the process of elimination and check for these issues one at a time until it’s identified.
So, while there are several issues an orange tree with yellow leaves can have, it usually comes down to one main issue. Figuring what the issue is may seem intimidating at first, but there are some simple steps to identify and fix it. Let’s take a further look at the common causes and solutions for orange trees with yellow leaves.
Causes of Yellow Leaves on Orange Trees
Like all citrus trees, orange trees are evergreen, which means they’re not supposed to lose leaves in the fall and winter like other fruit trees (also called deciduous trees). So, it can seem troubling if your orange tree has yellow leaves that are dropping.
Here are the most common reasons why orange trees develop yellow leaves:
- Weather or seasonal changes
- Transplant shock
- Lack of nutrients
- Disease or pests
At this point, you either know which issue your orange tree has and are looking for a solution, or you have no idea what could be causing it and need to start from the beginning. Either way, this guide is designed to help you identify and resolve it. Let’s get into the details and help make your orange tree leaves green again.
How To Fix Yellow Leaves on an Orange Tree
Reduce the Stress on the Tree
Similar to animals, plants can also go into shock when there’s a drastic change in their environment. This usually occurs from weather or transplanting the tree.
Orange trees can get stressed when there’s a sudden and dramatic change in the weather or temperature around the tree. Most commonly this means extremely cold or hot temperatures. Naturally, the time to watch out for this is in the changing of the seasons and in mid-summer or mid-winter.
Temperature swings of 30ºF can easily stress orange trees, especially if the temperatures rise above 90ºF or dip below 32ºF. The best way to prevent hot or cold damage to orange trees is to provide afternoon shade (when the sun is usually hottest) and cover them during frost.
If you have a potted orange tree you can move it inside, but make sure the temperature inside isn’t too extreme or sudden of a change.
The other common reason why orange trees get stressed and develop yellow leaves is transplant shock. As you’d expect, this usually occurs after initially planting the tree or repotting it (typically done every 3-5 years).
While transplant shock is almost guaranteed when digging up and replanting a tree, there are ways to greatly reduce the effects and the stress of the event.
Here are some quick ways you can reduce transplant shock:
- Be careful not to damage the rootball
- If the tree has a taproot, try to keep it intact
- Check that the new soil is loose and loamy (and not dead or collapsed)
- After planting, pack the new soil lightly
- Water generously after transplanting
Watering an orange tree can be a little tricky, especially if you live in a hot climate where the harsh sun can beat down on the tree (and the soil). And since citrus trees are subtropical and prefer hot climates, odds are you’re located in a warmer climate.
Yellow leaves are typically caused by over-watering, and not under-watering. In fact, this is the most common reason why orange trees develop yellow leaves.
A common issue with over-watering is root rot, which is a fungal disease that occurs in wet and stagnant soil. This actually happened to my potted kaffir lime tree and it started to develop yellow leaves. After seeing the water wasn’t draining and the soil started to smell swampy, I planted the tree in the garden and its leaves turned green again in no time.
So, how do you properly water orange trees and make sure they aren’t over-watered?
- Check the soil at least once a week
- Deep water to encourage deeper root growth and better drought-tolerance
- If the soil isn’t well-draining, elevate the tree by planting it on a hill or in a raised bed (for potted orange trees you can drill more holes in the container or repot it)
- Get a soil moisture meter so you don’t have to do the guesswork
Provide Balanced Nutrients
Unfortunately, when an orange tree develops yellow leaves, it directly affects the tree’s ability to photosynthesize. Yellow leaves reflect more light than green and aren’t healthy enough to have fully-functioning photosynthesis receptors. This leads to reduced energy and sugars to properly develop fruit.
Also, without the right nutrients, orange fruits can either be under-developed or start splitting.
The good news is that with a good fertilizer, your leaves and tree will become strong and healthy again.
Getting the nutrients right is one of the toughest tasks when it comes to caring for an orange tree. It took me a while to figure out the proper ratio and NPK (the three main nutrients for plants: nitrogen, phosphorus, and potassium). But, after some research and time testing different fertilizers (including a homemade fertilizer), I found a good balance.
When shopping for an orange tree fertilizer, the ideal NPK to look for in orange fertilizers is a ratio of 2:1:1. For example, a citrus fertilizer 6-3-3 is ideal for all stages of citrus tree growth.
Aside from its NPK, other indicators of a good orange tree fertilizer are:
- Well-known brand (such as Down to Earth or Jobe’s)
- Quality ingredients
With most store-bought fertilizers, and even homemade ones, there will be trace elements of other nutrients such as boron, calcium, and magnesium, so you shouldn’t need to worry about counting every nutrient.
Once you have a fertilizer in mind, know that the best time to fertilize citrus trees is just before the tree’s growing season. This will help prepare it for the nutrient demands that flowering and fruiting take on the tree.
Finding the exact month for the growing season can vary depending on the variety of orange you have, but you should be able to tell after the first year of fruiting. If not, you can always contact the seller to confirm the fruiting season.
Before applying a fertilizer, it can be helpful to know what to look for, so you can adjust the nutrients as needed.
Check That the pH Is Balanced
Before fertilizing, the first thing to do if check the pH is sufficient. After all, if an orange tree’s pH is imbalanced it will prevent the tree from being able to absorb the necessary nutrients. Too acidic or too alkaline will cause nutrient issues and imbalance. This can lead to issues such as yellow leaves. So, what’s the pH needed for orange trees?
The pH for orange trees should be between 6.0-7.0. While orange trees prefer a slightly acidic soil pH, it shouldn’t fall below 5.5. Alternatively, anything over 7.0 is too alkaline and can negatively impact the tree.
The easiest way to check the pH of your soil is to use a pH meter. To see which pH and moisture meter I recommend, you can check out my recommended tools page.
Common Nutrient Deficiencies
Aside from pH, there can also be issues with a lack of certain nutrients in the soil. If you don’t regularly use fertilizer for your orange tree, or use a poor quality fertilizer, it may have a nutrient deficiency.
Here are the most common nutrient deficiencies in orange trees:
Nitrogen is incredibly important for orange tree development, including its trunk, branches, and leaves. Primarily, nitrogen affects foliage development and a lack of it can lead to entirely yellow leaves.
Iron and Zinc
Iron and zinc are also fairly important to keep leaves green and the plant healthy. A common result of an iron or zinc deficiency is yellow leaves, but with green veins.
Again, secondary nutrients like these are commonly included in most citrus tree fertilizers, so if you’re using a good brand, you don’t need to go out of your way to add these nutrients.
Magnesium is another key to helping your orange tree leaves stay green. You can tell if your orange tree has a magnesium deficiency if its leaves have yellow or light green spots. Aside from providing a quality fertilizer, a good way to supplement your tree with magnesium is to use Epsom salts.
If you need help deciding on an orange tree fertilizer, check out my recommended citrus fertilizer page.
Check for Pests and Disease
After checking for any environmental stress, change in watering, and a good balance of nutrients, the last thing to check is for any signs of pets and disease.
Know that the most likely reason for yellow leaves on an orange tree is due to over-watering or a lack of nutrients, but there are some cases when a pest or disease can be impacting the tree.
The most common pests and diseases that can contribute to yellow leaves are:
- Root rot
Aphids and whiteflies can suck the nutrients out of leaves and turn them yellow.
You’ll know if your orange tree has aphids or whiteflies if the leaves are covered in small black or white bugs (usually on the underside of leaves).
Often the easiest way to deal with these pests is to spray them with a blast of water. Last year, my kaffir lime tree had aphids, and after spraying them with the hose (I just fitted my thumb over the opening to create a stronger spray), they fell off and died. They haven’t returned since.
Another method is to use neem oil, which coats them in a goopy oil, rendering them immobile and killing them off. It’s also safe for the plant. Also, consider introducing ladybugs in your garden as they’re a natural predator to aphids.
We’ve covered this briefly already, but for root rot (a fungal disease) just know that it’s almost always caused by over-watering. Elevating the tree or repotting it will help correct the soil and improve its drainage, further preventing this issue.
More Tips To Prevent Yellow Leaves on Orange Trees
- Add a 1-2 inch layer of compost on top of the soil to provide high-quality nutrients for the orange tree for the majority of the year. Sometimes, this is the only fertilizer you need.
- Add a 1-2 inch layer of mulch (on top of the compost if you’re doing that too). The mulch will not only break down into more nutrients over time but also help the ground retain water and block the sun from baking and killing the soil. This also means you can water your orange tree less often.
- Check your oranges tree for any changes in soil moisture and signs of pests and disease at least every two weeks. This will help you keep tabs on the tree and act quickly if something does happen.
- If you have dogs, don’t let them pee on the tree as urine is high in nitrogen and can (chemically) burn the orange tree. The excess nitrogen can lead to yellow leaves (this happened when our cattle dogs urinated on a shrub daily). If the tree is young, it doesn’t take much urine to cause damage.