We have many fruit trees in our backyard ranging from lemon to fig to avocado, and we’re finding they sometimes develop yellow and dropping leaves. To help fix this, I did some research. Here’s what I found.
Deciduous fruit trees like apples and cherries normally get yellow leaves in autumn. However, if they get yellow leaves earlier in the year, or evergreen fruit trees like citrus get yellow leaves, it’s likely due to over-watering, improper nutrients, a lack of sunlight, or pests and diseases.
So, while it’s normal for some fruit trees to get yellow leaves, when is it not normal, and what can we do to treat them? Let’s take a closer look.
|Deciduous Fruit Trees||Evergreen Fruit Trees|
Simply put, evergreen trees keep their leaves year-round while deciduous trees drop their leaves in the fall and grow them back in the spring. There are some exceptions such as semi-evergreen trees which are evergreen in warm climates, and deciduous in cold climates.
An easy way to remember if a tree is evergreen or not is if it’s originally a temperate or tropical plant. Plants that are native to the tropics typically experienced little to no frost, so they didn’t need to develop survival strategies during the winter (such as dropping their leaves).
For example, apple and cherry trees are temperate plants and require a certain amount of chill hours (hours under 45ºF) to enter dormancy and fruit properly in the spring. On the other hand, citrus and avocado trees are from the tropics, preferring USDA hardiness zones 9-11.
Most fruit trees that grow in USDA hardiness zones 8 and below are deciduous to survive the winters.
Certain evergreen trees can survive cold winters, such as pine trees, but they don’t commonly include fruit trees. For example, in the book, The Hidden Life of Trees, German forester Peter Wohlleben mentions the reason why pine trees keep their leaves through-out cold winters is that they’ve adapted to have a sort of anti-freeze in their needles.
So, if your fruit tree is deciduous and has leaves that yellow and drop in the autumn, know that this is a normal occurrence.
However, what if your deciduous fruit tree has yellow leaves in the spring and summer, or your evergreen fruit tree has yellow leaves? Which issues could be causing it then?
The most common reason why fruit trees get yellow leaves is due to stress from over-watering. This is especially common in soils with poor drainage. Over time, waterlogged soil can develop mold and lead to root rot (also called Phytophthora root and crown root). Root rot slowly decays the fruit tree’s roots, turning the leaves yellow and can kill the tree.
So, what’s the optimal way to water fruit trees?
The best way to water fruit 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. Water until the soil is saturated down to 2 feet deep. Additionally, provide 2 inches of compost and 4 inches of mulch such as leaves, bark, straw, or pine needles.
By watering only when the soil is dry, you’re preventing both under-watering and over-watering from occurring. Also, you’re helping the tree establish water independence.
Fruit trees that are watered with frequent and light watering typically only grow shallow roots. The reason why they do this is that there’s no need to grow deeper roots as the water is usually on the surface. This keeps the tree at a disadvantage as they are poorly prepared for windy weather and droughts.
So, if you want your fruit tree to be more self-sufficient and have a better chance of surviving the occasional drought, water it only when the soil is dry and down to 2 feet deep.
However, soils that have poor drainage (common with clay soils) can complicate this process.
You can determine if your soil has sufficient drainage with this quick exercise:
- Dig a 1-foot by 1-foot hole near the fruit tree (outside of its canopy to avoid root damage)
- Fill the hole with water
- Wait 1 hour
After the hour, if the hole is still holding water, the soil has poor drainage.
Generally, planted fruit trees in the garden are hard to amend as there are large volumes of soil (needing large amounts of amendments). Because of this, the best way to amend garden soil for better drainage is to apply 2 inches of compost on top of the soil every 1-2 months. Over time, the smaller particles will blend into the deeper soil. Avoid mulching at this time it can further lock in the moisture.
On the other hand, potted fruit trees with poor drainage can be amended fairly quickly by repotting them with fresh potting soil. Since the roots are limited to the pot, they generally don’t get as much transplant shock as digging up planted trees with spread-out and established roots.
But, what if we’re watering our fruit tree correctly? What do we check next?
3. Improper Nutrients
Excess nutrients are typically caused by over-fertilizing fruit trees. This can lead to the potential burning of the fruit tree’s roots, causing the tree stress and developing yellow leaves. Normally, fast-release fertilizers are the cause of over-fertilization as compost isn’t potent enough.
Lack of Nutrients
A lack of nutrients also causes the fruit trees stress, which then develops yellow leaves. Insufficient nutrients are commonly caused by poor soils, leaching, and other stressors. Nutrient leaching is when soils have too much drainage or are over-watered and the nutrients seep too far down into the soil.
The Best Way to Fertilize Fruit Trees
You can choose to fertilize your fruit tree’s soil with fertilizer or compost.
Generally, while chemical fertilizers have nutrients in quantity, compost has quality nutrients. What this means is that over the short term, chemical fertilizers can out-perform compost, but over the long term, it often causes soil damage. This damage leads to dry soil and decreased pest and disease resistance.
On the other hand, compost provides more than sufficient nutrients, increases water retention, and promotes healthy soils. For example, every 1% increase in the soil’s richness (organic matter) leads to 20,000 more gallons of water absorbed per acre (source).
Either way you go, if you’d like to see which fruit tree fertilizers I recommend, check out my recommend fertilizer page.
Aside from nutrients, keep in mind that fruit trees need a balanced soil pH (typically between 6.0 to 7.0).
The reason why fruit trees prefer soil with a slightly acidic pH is it’s ideal to dissolve nutrients 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
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 fruit 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 fruit tree’s soil is too acidic (below 6.0), add alkaline materials such as wood ash, charcoal, or lime.
Additionally, cold and/or wet soils are not good at promoting nutrient uptake as the fruit tree will either be slightly dormant during the cold or too stressed in wet soils.
4. Lack of Sunlight
Fruit trees generally require at least 6 hours of sunlight to photosynthesize properly. Without it, they’re unable to develop sugars to function properly and their leaves turn yellow. Over time, this low energy leads to the tree’s declined health which then can potentially die.
Tips to Increase Sunlight
- Plant the fruit tree in a south-facing direction for maximum sunlight (north-facing if you live in the southern hemisphere)
- Plant the fruit tree along a south-facing wall to reflect more sunlight and heat onto the tree (some heat even persists into the night).
- Prune any overstory trees that are blocking the fruit tree’s canopy. You can also prune the fruit tree itself to allow more light to reach the mid and lower branches. This new space increases sun and wind exposure, discouraging disease from spreading.
5. Pests and Diseases
Aphids come in multiple colors including white, yellow, or black, and usually hide underneath the leaves. Typically, they won’t cause damage to the fruit, but because they suck sap from the leaves, they can compromise its health— turning leaves yellow and reducing fruit size. Aphids also deposit honeydew, a sticky substance on the leaves and fruit.
The best ways to get rid of aphids on fruit trees are by spraying the infected leaves with water or neem oil, or releasing ladybugs. Most often, a jet of water is enough to get rid of aphids, but neem oil is a good second choice. Additionally, ladybugs are a natural predator of aphids and can reduce their numbers.
For more information on dealing with aphids on fruit trees, check out my recent post here.
Scab is a fungus that creates dark lesions on the leaves and fruits of fruit trees like pears and apples. The infected leaves yellow and fall off in the summer. Like other diseases, scab normally appears in the spring. The best way to prevent and manage scab is to prune and pick up any infected leaves and fruit.
A little-known secret is that some companion plants can help prevent apple and pear scab. Specifically, interplant chives around fruit trees to help control scab disease (source).
If you’d like to see more companion plants for fruit trees, check out my other post: The 10 Best Companion Plants for Fruit Trees.
Apple cedar rust is a fungus that spreads from juniper trees (also called cedars) to apple trees and causes yellow and dropping leaves. The spores are carried from one tree to another in the spring when it’s warmer and rainy. Cedar apple rust can be treated by reducing nearby juniper trees and by using fungal sprays.
Other fruit trees can also get different variations of rust.
This disease is most common in the Northeast US and especially affects more rural areas that have both farmland and forests. It’s not uncommon for fruit trees to be severely affected by this fungus and it can even live dormant during the fall and winter.
While leaf spot typically causes dark, red spots, the stress of the disease commonly leads to yellowing and dropping leaves (source). This disease is most common for cherry and plum trees and occurs in late spring and summer. Leaf spot can be either fungal or bacterial. Because of this, fungicides won’t work on bacterial leaf spot.
As with most fruit tree diseases, pruning the infected leaves can slow the disease.
A Note on Pesticides, Herbicides, and Fungicides
Even though chemical sprays are an easy way out, like all easy and convenient things, there are usually long-term costs. Namely to the plants, soil, and surrounding beneficial life. Before using conventional sprays, weigh the pros and cons and consider using organic or permaculture-based treatments first.
Along with the above sprays, here are some of the most effective organic methods that I’ve found to manage yellow leaves on fruit trees and other plant diseases:
- Minimize tree stress (use best practices such as deep watering, composting, and mulching)
- Homemade whey spray
- STUN method
If you’re interested, I’m adding two videos below so you can learn more about organically managing diseases on fruit trees.
Homemade Whey Spray
Stefan Sobkowiak – The Permaculture Orchard has a great video on a safe, homemade, and most importantly—effective fungicide (hint: the secret ingredient is whey).
Mark Shepard, on his 100+ acre farm, uses a method called STUN (sheer total utter neglect) and it works wonders for him. He uses no chemical fertilizers, sprays, or any other dependencies. Through the struggle, his fruit trees become stronger and his job gets easier.
Check out the below video for more about Mark Shepard and STUN.
As always, if you get stuck, reach out to your local nursery, professional orchard, or local cooperative extension service. They’ll have more specific knowledge of the common issues of fruit trees in your region.