How should a lemon tree with yellowing leaves, peeling bark, and small fruit be saved?

Question

Our lovely lemon tree is in trouble... We live in Northern California. Starting mid-last summer our tree began yellowing.

We've called an arborist out to the house but the advice has been pretty useless. (Advice was to turn off all yard sprinklers near the tree and nothing else to recommend. We did this and if anything the tree seemed to be getting sicker.)

Here are the symptoms:

1. Most leaves are turning yellow and very few leaves at top of tree.

2. The fruit is smallish relative to past season.

3. The bark is peeling starting from the base of the trunk and going up.

We have supplemented with Iron/Magnesium solution per directions on package (1% by volume) two times over two months, total volume of 2.5L poured around base tree and roots. This has not seemed to help the color. I measured the soil pH and best as I can tell from the kit it seemed normal within range for citrus trees. Also, there seems to be a green mossy color on the branches. We're not sure if this has always been there or if it's getting worse.

Questions for StackExchange include.

1. What is wrong with our tree?
2. What is causing the bark to peel? Is this "collar rot"? Something else?
3. Are the yellow leaves related to the peeling bark at base of tree?
4. How can we fix the bark, the leaves. Basically, how do we save the tree?

We're not gardeners but we love this tree... please help if you can! Any advice, questions or treatment options?

Yellowing Leaves

Smallish Fruit

Peeling Bark

Formula we used to supplement at 1% by volume

 (total treatment volume 2.5L at base of tree two times over two months)

Answer 1

I live a long ways from Northern California but these symptoms are the same for citrus grown anywhere in the world when the soil is alkaline. There are some great pictures here.

The most likely cause is a manganese deficiency

Leaves turn yellowish overall but larger veins remain slightly green where manganese is deficient. Zinc deficiency symptoms are somewhat similar to those of manganese deficiency. Both are more prevalent on young leaves of the fall growth flush as soils cool and root activity diminishes.

Solutions:

• improve the soil quality around the tree by adding organic matter, the photo shows chunks of soil, not an even texture
• apply a foliar micro nutrient spray about every 3 to 4 weeks. Apply a chelated citrus fertilizer high in nitrogen that also has micro nutrients. Foliar sprays are just water and fertilizer sprayed on the leaves for faster absorption
• examine the area for external causes of soil compaction and loss of organic matter. Are people always walking over the root area? Does water poured on the soil drain freely or does it puddle and take a while to drain?

Technically speaking I believe you are seeing chlorosis induced by a high ph level in the soil (over 7 ph). Another part of the solution may be using a fertilizer specifically designed for citrus trees. Over a ph of about 7 iron, manganese and zinc that are water soluble are not available to the tree. You need a chelated micro nutrient mix. I have not used this product but have seen it recommended in other forums.

I don't know what is causing the bark to peel off.

Your tree could benefit from some pruning.

• In the first picture I see a tree that needs thinning to encourage larger fruit and let more light go through to the lower branches.
• In the last picture I see a stub coming out of the main trunk that is an entry point for rot and a longitudinal sunken area on a branch that I normally associate with mechanical damage.

Citrus trees are heavy feeders and don't do well in very alkaline soils. More micro nutrients year round and more fertilizer during the flowering and fruit season would seem to be indicated. I urge you to consult with a local nursery or citrus grower to get a local opinion as soil chemistry and diseases can be very localized.

Answer 2

You might try sanding the soil..kinda like pounding spike holes into the ground and adding sand into the holes..pound at least 100 holes for a tree this size down at least 3ft with a metal spike .. fill in with fine sand..and maybe some fertilizer (kinda like a fertilizer spike with sand setup). I would use osmocote type to make sure it is released slowly. You need to remember citrus needs great drainage..sanding will help..break up top soil with pitchfork every 6 months and add sand here as well to increase aeration.

Remember, when trees and plants are watered three things happen, water is brought to the roots as is nutrients such as fertilizer but don't forget the water also brings oxygen to the roots also..they need to breathe so don't drown them.

If you have a septic tank that can also kill your tree..it changes the drainage and the added raw sewage kills citrus..( this happened to me once when a neighbours sewer line broke and killed my orange tree kinda like how your tree looks like...similar symptoms with slow death. Right now the moisture is a problem with your tree so sand it out to improve aeration. JMHO

Answer 3

First and foremost, the tree is getting way too much water. The soil must dry out between waterings. Water should be on a regular schedule so the roots can depend on it.

For fertilizer, simply use a 15-15-15 fertilizer broadcast around the tree. I have had trees like this, and I now mulch around the tree and water once a month during the summer (I'm in So. Cal), and not at all during the winter unless the leaves begin to curl or I am fertilizing. To fertilize I use a gloved hand filled with fertilizer and throw it in the darkened wet area (turn on the sprinklers to see where to put the fertilizer.)

I still have those trees but the problems you are suffering no longer exist (the bark damage does but is not a problem.) The bark may grow back some but not much. The amount of (vertical) bark that will support the crown is surprisingly small. The mulch will reduce evaporation and minimize temperature swings. The feeder roots will neither drown nor dry up and wither so the tree will need water less frequently and to a lesser extent.

The other remarks above about the Ph are interesting since the lemon trees I have drop all kinds of fruit and the alkaline soil gets really doused with a ph lower than vinegar. I should test it I suppose but this approach works to greatly reduce watering from 5 hours every two weeks to an hour a month in the summer and none the rest of the time. As a PS to reducing watering trimming the tree back will make it healthier too, for many reasons as, well as lessening the weight of the fruit causing limbs to break.

Answer 4

Yikes. That soil is really moist and the moss/lichen growing on the trunk along with the missing bark from a good chunk of the base of the tree indicates moisture is your issue. That tree is way too moist and it looks like you've already eroded at least half of the bark/cambium of the trunk. This results in diminished nutrients making it up the trunk which results in tree decline and eventual death. My advice is to go purchase another lemon tree to replace this one, thats the easiest path. And if you see moss/lichen growing on the trunk lower the water it receives.