Mexican Lime Tree

Good evening all. My name is ZEEK. I am new here on the forum. Thank you for allowing me to engage and ask questions. Here’s a little bit about myself. I am a 43 year Old husband/father who recently moved to SoCal a little over 2 years ago. I had a heart attack in 2016 and since then I have been put on a heart/lung combo transplant list. I am improving and at this point they may remove the lung portion of the transplant.

I started eating a plant based diet before moving here. Once we moved here I couldn’t believe the abundance of citrus trees I saw in people’s yards, it blew me away. I purchased my first eureka lemon tree one year ago this month.

A few months after that I purchased a Mexican lime tree. It has been growing vertically and there are 5-6 very small limes that have grown on it. Here are my issues:

Many of the leaves have the bright yellow discoloration as you see in the pictures attached. I also had many leaves curling under. Another thing I’ve noticed are ants. I removed what looked like hard honey the size of a jolly rancher. I hosed the tree off and sprayed neem oil all over the leaves(over and under mixing it with the right amount of water required. I fertilized it in September(as the instructions on the bag suggested) with a citrus fertilizer. In the past I have sprinkled egg white shells, coffee grounds, and some rabbit manure in the soil. I do not over water them. Both trees, and the new Dancy tangerine tree I got for my birthday are all growing in pots. I TRULY love my new found hobby. If you guys have any suggestions regarding what I need to do to help my lime tree I would greatly appreciate it. Thanks so much!

First, I admit I have no idea what is wrong with your tree.  

That said......Do you have anyway to plant this tree in the ground rather than in a pot?

My family has citrus planted in the ground in Upland California and we do not give them any care whatsoever.  They seem to thrive and produce fruit without our help.

I'm inclined to believe that since you've used a citrus fertilizer, and the tree still exhibits symptoms, that perhaps the pH of the soil isn't where it should be. Citrus trees seem to like a pH around 6-6.5. Aside from a lab soil test, a simple pH meter from a garden center should be able to give you a ballpark idea of where the pH is. If a citrus trees soil pH is too acidic, or neutral and going alkaline, the nutrients it needs become less available. You could also use litmus paper to get again, a ballpark idea of the pH, but nothing precise. Take a small amount of the soil, mix with a small amount of distilled water, and then test it with what are generally called pH test strips. It will change color, and you can compare the color to the chart on the side of the container.

If the soil pH is about where it needs to be, then my other suggestion is a lack of microbial activity in the soil which convert nutrients in soil to forms available for plant uptake. A Bacillus and Mycorrhizal inoculant will really help the soil and tree thrive. They're readily available on the internets and even some big box stores and garden centers.

The tree shows the signs of manganese deficient soil, use about a quarter cup to a half cup of Epsom salts around the tree at 12 inches from the trunk, this should be done once a year just for general health and vigor of the tree.

James give great advice for any citrus grower.

Redhawk

Hey Redhawk, did you mean to say magnesium instead of manganese? Aren't epsom salts for adding magnesium?

Yes James, Epsom salts are MgSo4 (magnesium sulfate) but my current study is showing that there are some bacteria that feed on the magnesium and that somehow triggers another set of bacteria to break down tightly bound (not readily testable or available to plants) manganese.
I just happened onto this possible relationship between bacteria last year while doing some testing of my soil in a portion of my orchard (pears and plums), my test showed that an area I had just made an Epsom salts addition to the top of the soil, was low in manganese. Prior to the test and post application time there had not been any rain and since I don't usually water that part of the orchard there had not been any incorporation of the magnesium sulfate as yet. Three days after the next rain, I ran the soil test again and it was one of those woah moments, there was not only free magnesium in the soil but there was a 14 point rise in free manganese as well, something I did not expect. I am currently investigating the bacteria in that soil, I suspect there is a symbiotic relationship between these different bacteria that causes one type to excite the other type and that is where the manganese gets released.

In most soils there can be many minerals that normal soil tests don't pick up because they are so tightly bound into multi component molecules. I've seen some pretty wild results over the last 40 years in soils that didn't show any of several minerals only to have them show up in fair amounts once the soil biology began to get really good. This sort of "magic appearance" is what formed the basis of my current research project. If results keep pointing to these interactions between bacteria species and types it might provide more knowledge about just how the soil organisms work together to form the nutritional bubble needed by plants.

Redhawk

I think that's fascinating. There seems to be so much about soil biology encompassing all the different soil life forms and how they interact that science doesn't understand and is constantly making new discoveries about. I think soil is amazing.

Bryant, you are making us all look like layabouts!

Super interesting. I need to post some fig pix so you can see what your advice has wrought...

Hi Zeek.

I live in the same area as you, so let me take a shot at your concerns.

First, ants are a part of the picture here in SoCal.  They farm aphids by carrying them up to the tender young leaves and placing them there.  Then they suck on the butts of the aphids to draw nectar out (I KID YOU NOT).  Argentine ants are all over, and their colonies can become absolutely massive.  Unlike bee colonies or other insects, Argentine Ants can have upwards of 1000 queens.  They just keep adding rooms below ground and continue to hive off more and more queens.  You can drown them or if you find a non-toxic organic pesticide, they die easily enough.  Fill a 5-gallon bucket with water, put just a cap full of the ant killer in it, and flood the ant colony.  Do this about 50 times and you'll take care of the problem.

Once the leaves are older and tougher, the ants don't like them as much because the aphids can't suck on them as easily.  

Leaf cutters make those little whitish squiggly lines on the tops of the leaves.  Once you get some spiders in your trees, the leaf-cutters quickly go bye bye.  But don't freak about aphid and leaf-cutter damage: curled up leaves are still working --- they are still photosynthesiing sunlight.  Ugly, yes, but still making sugars for the tree.

Second: The problem of fertilization.  Citrus trees are nitrogen pigs.  The yellowing you see on the leaves may be a lack of N.  But when you hit them with a shot of heavy nitrogen, then you get a flush of green growth and then you get a flush of aphids.  The reason the leaves are curled up like that is because the aphids are on the underside of the leaf, sucking away.

The cure?  Pee around the drip-line of the tree.  Urine has the right amount of nitrogen to help the trees grow, but doesn't seem to hammer the tree all at once and send it into super-growth-mode.  Pee is free and it's wonderful for the soil food web.  If peeing around your trees isn't your thing, coffee grounds will slowly release N.  Or build your compost pile right on the ground near your citrus trees, and then as you turn the pile, move it around the trees --- the walking compost feeder.

Third, citrus trees are evergreen, but they still will lose their leaves in time.  So when you see yellowing leaves, that's just the trees way of saying that these leaves have served their purpose and now its time to get ready to drop them.  I don't know this for a fact, but my sense is that citrus leaves hang around for about 2 years before dropping off, but you really don't notice because they are constantly being replaced.  Don't pick them off.  Don't do anything.  They'll drop off when they are ready.

Fourth, water.  Citrus trees do not like to be sprayed with water.  If you have lawn sprinklers that are hitting them, try to direct the spray around the root zone but not directly onto the foliage.  They like EVEN moisture.  Citrus trees don't want to be waterlogged.  Plant them about 4 to 6 inches above soil grade, and then gently slope the soil upwards toward the trunk of the tree, out to a distance of about 4 feet or so.  That will mean that for the first 2 years or so, you'll want to give them a good drink with the hose once or twice a week.  If its a baby tree, maybe even every 2nd day in the August and September when its so stupid hot in Los Angeles.  But once established (4 years or so), you can really back off with the water.  What really helps is . . .

Mulch.  Fifth -- mulch helps maintain a consistent level of moisture in the soil.  As said above, spiking the water up and then drying things out, up, down, yoyo moisture . . . not a good thing.  I mulch HEAVILY once or twice a year with wood chips.  8 to 10 inches deep.  Don't pile them up around the base of the tree, but get a heavy blanket of bio-mass on the ground all around your tree, well past the drip line (the outside edge of the foliage growth).

Our So. Cal. soil is heavy clay.  If you consistently mulch with wood chips, you'll notice how amazing the soil gets in a couple of years.  That's not much of a help immediately, but take a long view.  Even in 6 months you'll see how much better the soil has gotten.  A heavy layer of mulch will also transform your soil to a fungal dominated soil system.  Fungi help turn that carbon biomass into nitrogen rich plant food.  Worms will integrate the biomass into the soil profile.  

FEED THE SOIL -- not the tree.  Mulch/compost on an ongoing basis.

Sixth: companion planting.  You want to attract ladybugs, spiders, wasps and praying mantis's.  That's why you never want to spray the aphids on your tree.  You can blast them off with water but don't start spraying toxins all over or you'll kill the very guys you want to come in to save the day.  Google "Lady bug friendly plants" (or some such) and you'll find a list of things to plant around your citrus.  I'm not so intentional --- I just have a bunch of different stuff growing around my orange trees, and it seems to do the trick.  Carrots and fennel are left to go to seed.  Other veggies like peppers (which will grow for 3 years in So.Cal.), beets, and russian kale are currently growing all over in my citrus area.  The mulch will help create habitat for good insects (predator insects).  So while the temptation is to have a perfectly clean understory below the citrus trees, don't make it so clean.  You might as well grow some stuff you can eat.  I had nettles out there for awhile, but my wife was always stumbling into them and I wasn't very crazy about them.  Comfrey, society garlic, herbs like chives, thyme, rosemary, etc. do well beneath citrus.

Further, companion plants within the root zone of the tree will pump sugars down into the soil profile, feeding the microbial food web and fungal networks.  A beet isn't going to outcompete the tree for nutrition or sunlight.  A creeping herb like thyme or oregano will only enhance the soil fertility.

Finally, patience.  These trees may take a couple of years to get rolling.  If you pee around them regularly, you'll see them get a jump start.  If you get an aphid infestation, just hose them off.  Baby the trees for a couple of years, and then once established with a healthy mulch layer and companion plants, you'll be able to virtually ignore the tree.  I do.  I never do much with my citrus anymore other than take a leak around them.

My hunch is that some of that yellowing is due to too much water.  If the soil is moist, take it easy with the water -- particularly during this time of year.  

You'll have more limes than you know what to do with in two years.  Hang in there.