One of the most common questions we see from new citrus tree owners in their first season is "Why is my citrus tree dropping yellow leaves?" Here is a brief explanation that will hopefully help you have a better understanding of why citrus tree leaves turn yellow and drop.
While citrus trees are classified as evergreen, there is a regular life span to citrus tree leaves that lasts anywhere from 12 to 18 months with some lasting as long as 4 years on a healthy tree before they shed. Since most citrus trees leaf out in the spring and fall, it is expected that you will see a large amount of leaf drop during this time as well. During this time of year, old citrus tree leaves will go yellow as the tree pulls out as many nutrients as possible to reuse elsewhere in the tree in preparation for leaf drop. During this time, you should also see new growth come in to replace the last season's growth. This new growth will shade outgrowth from the previous seasons and cause older leaves from within the canopy to drop as well. All of this is to say that some leaf drop is normal and you should see it nearly year-round with most dropping in spring/fall.
Abnormal leaf drop can be caused by several factors including exposure to extreme changes in temperature, lack of water, over watering, lack of nutrients or nutrients imbalance, wind, root disease, pests including insects and rodents, systematic diseases, or even damage from spraying.
Set your expectations according to your situation. If you are taking your tree out of the box for the first time or moving the tree to a new location, then you should expect some amount of leaf loss as your tree acclimates to its new home.
The ideal temperature range for citrus trees is between 32°F & 85°F. Protect your tree from sudden changes in weather. If you live in an area that regularly drops below 32°F for more than a few hours in the winter, then you will want to consider growing your tree in a container so that it can be moved inside and by a sunny window during winter. Cold temperatures can also cause citrus foliage to turn yellow in color. While citrus trees can tolerate much higher temperatures, they are naturally understory trees in the forests that they are native to, so direct sun in combination with temps above 85°F can cause sunburn & defoliation. You need to protect your tree from intense sunlight exposure when temperatures are above 85°F with some kind of shade cloth or tree paint & foliar spray.
If your tree is overall yellow in color, it could be due to a lack of or excess of water or due to nutrient imbalance or deficiency. If you are not already feeding your tree regularly, apply a monthly dose of citrus fertilizer like Romeo Plant food.
Most insects can be treated easily if you use insecticidal soap. Insects like scale adhere themselves quite well so you need to spray them then give the infested area a quick wipe down with a rag.
When dealing with wind, you want either move the tree to a protected location or protect your tree with some kind of physical barrier. You will also need to make sure that your tree is properly staked which may require upgrading the tree's current stake with a larger one.
Check out our Citrus Growing Tips for more information.
Get in the know about HLB(Huanglongbing / Citrus Greening Disease) and help save your community's citrus. Only source citrus trees from reputable growers.
Author Israel Osuna