Last week, I visited the largest organic avocado farm in California. It’s those hills in the photo above — they’re covered with 1,000 acres of avocado trees. And I felt vindicated when I saw that they care for the soil under their trees in essentially the same way that I do.
But I’ll get to that in a minute. First, let’s say what our goal in growing an avocado tree is. For me, it’s a consistently fruitful tree, which means it must also be healthy. And how does soil fertility affect our achieving this goal? Avocado trees, like all plants, need certain elements to run their systems properly and produce fruit. So we add stuff to our soil when necessary.
Which nutrients avocados need
“California soils contain ample amounts of most plant nutrients,” writes Paul Moore in the 1952 Yearbook of the California Avocado Society, the Bible of avocado culture. “The function of fertilization is to supplement deficiencies in the soil, not to feed the tree directly with all its nutrient requirements. The most common deficiencies suffered by avocados are nitrogen and zinc.”
So, the soil in your yard may have all your avocado needs, but commonly in California, avocado trees need added nitrogen and perhaps zinc. How do we know if this is the case with our own particular soil?
You can get a sample of your soil (or leaves) tested by a lab such as San Diego Agricultural Laboratory.
More easily, however: “Your trees are open books. If you learn to read them you will be able to tell their nutrient needs at a glance. For example, nitrogen deficiency is indicated by pale green or yellowish green leaves. This is in contrast to the normal dark green color of leaves formed under an adequate supply of nitrogen.” (That’s Paul Moore again.)
But maybe you’d like to give it a little boost, a little extra just to make some bonus fruit? It doesn’t quite work that way.
In the book Avocado Production in California, former University of California farm advisor Gary Bender writes, “It should be remembered that there is no “magic bullet” fertilizer that will increase avocado production, unless that particular grove has a deficiency in a particular element.”
Fertilize only as needed
Extra fertilizer will not help and it might hurt. For example, studies on avocado tree responses to different levels of nitrogen fertilization have found roughly the same results for more than 50 years now. T. W. Embleton and others wrote back in 1958 that they found that “. . . too little or too much nitrogen results in a reduction in yield, and highest production is obtained with a moderate level of nitrogen in the trees.”
More recently, a study by Mary Lu Arpaia and her colleagues, published in the 1996 CAS Yearbook, additionally found that “. . . fruit size from the high nitrogen trees tend to be smaller.” Also noticed was “a decline in post harvest quality of the fruit coming from the trees high in nitrogen.” The term “post harvest quality” refers to things like ripening properly with normal coloration and without rotten spots.
Therefore, to achieve our goal of a healthy tree that produces much fruit, we can periodically test our soil and leaves, but more easily we can simply keep an eye out for foliage that lacks the expected, uniform deep green color. What isn’t called for is blindly adding fertilizers as a matter of routine. Adding more than enough is not better.
Fertilizer can’t solve all problems
And if we see symptoms of a nutrient deficiency? What do we do then? Still, before jumping to the conclusion that soil fertility is the problem, assess your care of the tree, especially your watering practices. As Bender notes in Avocado Production in California, the exact same symptoms as for nitrogen deficiency “are also associated with other problems such as Phytophthora root rot and root asphyxiation due to water-logged soils. In these cases application of nitrogen will not fix the problem. If nitrogen deficiency is suspected, it should be confirmed by leaf analysis and an examination of other cultural problems in the grove.”
I’ve seen many trees that appeared sickly, yellowish, nutrient deficient, only to poke into the soil and find it soggy. That’s a watering problem, not a fertility problem.
Here’s a specific example. This tree wasn’t watered often enough when first planted, so leaves burned. Then it was watered too much too often, so now it has yellowish foliage.
Fertilizer need not apply.
(You might like to read my post, “How much and how often to water avocado trees in California,” to get a better handle on that. Also see, “Avocado leaves turning brown? Here’s why and what to do.”)
And we can’t forget about the weather. Both freezing temperatures as well as extreme heat will discolor leaves. Nor can we forget that avocado leaves don’t live forever, and when they begin to die, they turn yellow before falling off. Here’s a photo of a healthy, but naturally dying, avocado leaf:
When I was new to growing avocados, I saw such a senescent leaf on my tree and worriedly sent a photo to an expert for advice.
Lack of fruit, as a single symptom, should not be taken as caused by nutrient deficiency, by the way. Avocado tree fruit production is always fluctuating due to natural alternate bearing, more and less conducive weather, bee activity, etc.
After all of your care for the tree has been considered, and you’ve gotten your hands dirty feeling the soil and judging your watering practices, and the last possibility is that your soil is deficient in a nutrient, then . . .
Two main ways of supplying nutrients
. . . you can feel confident that buying a fertilizer product that will improve things. Go to a nursery and they should be able to provide you the right product. I’ve seen innumerable beautiful and fruitful avocado trees in both yard and farm settings fertilized with E.B. Stone’s Citrus and Fruit Tree Food. You might try that. Apply it by following the label directions. And do note that among its primary ingredients are chicken manure and bat guano.
On the same day that I visited the large organic avocado farm pictured above, I also visited a smaller organic avocado farm. At the smaller operation, the farmer told us that he fertilizes his trees using Peruvian seabird guano that is injected into his irrigation system. In addition, when he planted his trees three years ago he had added a layer of wood chip mulch. “I wish I could add more mulch because I’m really convinced that it increases the soil’s cation exchange capacity,” he said.
Some mulch around his trees, but more would be better, the farmer says.
He wishes he could add more mulch? What’s stopping him? Even if he gets the mulch for free, imagine the costs of spreading such a bulky material under hundreds of trees. Injecting fertilizers into an irrigation system is far cheaper.
Nonetheless, beneath the tens of thousands of avocado trees at the other farm, the largest organic avocado farm in California, there is new mulch being added consistently. They make their own right there on the farm. Using massive, expensive machinery, they take green waste (pieces of plants and trees), mix in some animal manures, compost it in long heaps, and eventually spread it under their trees.
As I mentioned earlier, I felt a sense of vindication seeing such a large operation treating their trees this way because . . . look what’s under my trees.
Keeping it thick.
Even around the babies, I build it up.
Under all of my avocado trees, I keep a thick mulch of wood chips. In addition, especially under young trees, I add some compost or manure. Often, it’s chicken manure or what I call “chicken compost” from my own birds. I find that this gets young trees growing well until the wood chips break down enough to start feeding the trees more.
Here is a video showing my typical application of compost and mulch around a newly planted avocado tree.
In Avocado Production in California, Gary Bender writes, “Nitrogen is also available to plants from the breakdown of organic matter in the soil. Soil organisms convert proteins in the organic matter to ammonium compounds in a process called mineralization. California soils are historically low in organic matter, so this aspect is not too important unless organic matter is added by way of mulches or manures.” (Italics are mine.)
The large avocado farm uses a special machine to blow out and spread the mulch and composts under trees, saving time and labor. But it remains a much more expensive way to add nutrients to the soil.
There is a bigger economic picture to see, however. The mulch not only breaks down to add nitrogen and other elements in order to act as a fertilizer, but it also functions as an herbicide by covering weeds, as well as a soil conditioner that improves water intake and holding, and a disease suppressant, etc.
How much is all of that worth beyond the fertility effects alone? We are killing many birds with one mulch stone.
(You might like to see the short article, “The Economics of Mulching.”)
Which organic matter to mulch with
What organic matter should you add as mulch? I say, vary your sources. Don’t add a single thing year after year, which can build up too much of one element and not enough of others. It can lead to the tie up of some elements or toxicity in others. Vary your sources, just as the large organic avocado farm does. (Just as is done in nature. This is nothing new.)
I add a little horse manure from my neighbor occasionally, a bit of my chickens’ manure, plus a lot of random plant materials. But more than any other single element, I mulch with lots of wood chips from tree trimmers. This stuff is bulky with big chunks, and avocado roots enjoy this characteristic for two reasons. It ensures that the mulch remains airy. You’ll find roots poking their heads up into it. The chunks of wood also feed bacteria that consume the wood’s lignin by producing an enzyme called cellulase, and this enzyme breaks down the cell walls of the fungi Phytophthora cinnamomi, the organism that causes the root rot disease in avocados.
(I recently wrote the post: “Where to get wood chips for mulch.”)
Our guide on the tour of this large avocado farm’s mulching operation was the farm’s manager along with Mary Matava, who has been working with fertilizer, mulch, and avocados in Southern California for four decades. She is an agronomist and the owner of Agri Service, the company that runs Oceanside’s El Corazon compost facility.
Matava reminded us to consider the avocado’s sensitivity to salts when mulching. Wood chips and greenwaste compost are usually low enough in salts to not worry about (although greenwaste compost can be surprisingly salty if it is made in a hot and dry location using salty irrigation water), but mushroom compost and manures should be applied with more caution as they are higher in salts.
If applying mushroom compost or manures, it is ideal to apply them in winter so that the rains can leach the salts, said Matava. About five inches of rain (or irrigation water) should suffice. Then come spring, when avocado roots again become more active, the roots won’t have to deal with salty soil as the salts have been driven below the level of the roots.
(Read an excellent article that Matava wrote: “Mulching Practices in Avocado Orchards.”)
How much mulch to add
As for how much organic matter to add to the surface under your avocado tree, that’s hard to calculate with any precision without some serious testing and quantifying of the materials. I don’t bother. I merely make sure that the soil is always covered. I add more materials whenever the layer is thinning out. This very simple approach has worked well for my avocado trees.
After a few years of constant coverage, the mulch-soil interface layer starts to look and feel like a forest soil. Intuitively, you look at the color, you smell it, you feel it, you just know it’s fertile.
Black, fragrant, sticky, able to give the tree all it needs.
And some good news: Gary Bender writes, “However, it is not necessary to apply the same amount of organic matter each year because mineralization of nitrogen, after a high release rate the first year, declines to a release rate of 5% – 6% per year from the initial application. Therefore, as the years go by, application rates of organic matter should gradually decline so as to achieve a steady release rate on nitrogen in the soil.” The organic matter sticks around, quite literally, and is able to feed your tree for longer than other fertilizer options.
Why did I feel “vindicated” upon seeing the investment into mulching that the large avocado farm had made? I was low on self-confidence, I suppose. I had been the only one I knew growing many avocado trees without adding fertilizers, with only mulching, and I wondered if I was fooling myself — despite the fact that I could see my trees growing and producing well year after year.
I’m now feeling more confident in the long-term sustainability of the way in which I fertilize my avocado trees, which is to not fertilize them at all, in the sense of adding what we usually think of as fertilizer. Rather, I merely mulch.
Mary Matava again, this time in an article she wrote for the California Avocado Society’s 2009 Yearbook, “The Benefits of Mulching Avocados”: “In fact, the feedback from growers using mulch is that they reduce or eliminate the need for inorganic nitrogen with no reduction in yield.”
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thanks for this article. the fruit production on my avocado trees have been in decline lately so was trying to figure out why. Also that heat wave a few months ago in socal didn’t help specially with all the baby avocados that were just starting out. 🙁
good reminder to switch up the fertilizer and i’ll check out the EB one.
been trying to find a cheap source of mulch though. need to cover a good amount of space. harder to find organic mulch (or is that not necessary?) local big box stores only really have the Kellogg’s Gromulch that i can find. would that work?
Hi Johnny,
2018 has been an anomaly, no year to judge avocados by in general. It has been the worst year in my personal experience. Hope it stays that way.
Have you seen my post, “Where to get wood chips for mulch”?
As for organic, it is my understanding that certified organic avocado farmers are able to use any mulch that has gone through a composting process that is hot enough to kill pathogens and break down pesticides even though some certifiers give growers a hard time about this. As for whether that’s acceptable to anyone personally is another issue. Realistically, the only way you’re going to know the sources of any mulch is if you create it yourself, which is possible but pretty difficult if you need a large quantity.
thanks..been on the chipdrop list but been afraid to confirm and then find myself one day with a giant load of wood chips haha. i’ll keep my eye out for tree trimmers and see how that goes!
Beware of ChipDrop.
I used it the first time and got a GIANT load of chips.
The second time the load consisted of some chips and a mix of pine needles, unground palm fronds, and empty beer and soda cans.
Hi Greg-
Question: My Reed has been in the ground for almost a year and is about 6 ft tall. I noticed over the past to weeks some yellowing on about 30% of the leaves on my tree- They’ve turned a kind of light green/yellow but the other 70% are perfectly dark and with no signs of trouble at all. Should I be concerned?
Hi Greg-
Question: My Reed has been in the ground for almost a year and is about 6 ft tall. I noticed over the past to weeks some yellowing on about 30% of the leaves on my tree- They’ve turned a kind of light green/yellow but the other 70% are perfectly dark and with no signs of trouble at all. Should I be concerned?
Hi Vincent,
Probably nothing to be concerned about. Do the leaves look like the photo of Reed leaves toward the bottom of this post? Sounds like a few leaves just dying a natural death.
Hello,
I’m new to growing ? avocados, that new that I’ve only killed two out of two…
I’ve been trying to grow them in pots,I’m in Australia ..Let’s hope the next one I will b able to get some fruit off it or even better not kill it with in weeks of buying it…
Thanks,I will try again.
Thanks for the great info. I’m new to growing avocado trees having moved to Fallbrook 2 years ago. I’ve been working on getting the trees on our property in shape with knowledge gleaned from your posts.
Were the big growers affected by this summer’s heat?
Hi Rey,
No doubt that July heat hit the big growers just as it hit us. I’ve driven around a lot in the past few months looking at avocado farms between San Diego and Santa Barbara and seen a spectrum of grove health.
A couple of patterns are obvious. The closer the trees are to the beach, the less they were affected by the early July heat simply because there wasn’t as much heat there. It only got to around 100 near the beach, which is nothing compared to the 115-plus experienced inland. While driving the 126 through the Santa Clara River valley I saw perfect groves near Ventura and scorched groves near Piru.
Also, people who were on the ball with watering their trees before and during the heat came through pretty well. Specifically, they may have lost fruit, but they didn’t lose full trees. I’m inland, where it got to 117, and I lost some fruit, but thank God, I didn’t lose any trees.
We have used the free mushroom compost from Mountain Meadows Mushroom farm in Escondido in years past. Free is a great price! But thanks for the tip to change it up and not always use the mushroom compost.
Hi Emily,
Thanks for mentioning the mushroom compost. I had wanted to say something about its saltiness as well as the salt levels of manures — salt levels being important since avocados are so sensitive. This afternoon I’ll add some information about that in the post.
Greg – Tell everybody to take it very easy if they get any free horse manure.
That stuff killed a Mexicola I planted a few years ago and the second one I killed by mixing too much compost in the soil. My conclusion is that “Your the guy to ask about growing avocados, I’m the guy to ask about killing avocados.”
The first rule of fertilizing anything is ” A little is good – but a lot is always bad”.
Hello, Greg!
Thank you for taking the time to write these posts!!! My Kona Sharwill avocado that I got from Atkins Nursery, per your suggestion, is growing like crazy(300%+ growth). My Reed avocado has very green leaves but no desire to grow like crazy as the Sharwill. It seems to me they are doing good/wonderful because of the thick layer of wood chips that I put on top of their soil. I live in a city and horse manure is not readily available, so EB fertilizer will be considered, If my trees ever need help. I will be watching closely because despite of all my efforts, I don’t have fruit to show for it yet.
Hi Wai Ling,
That’s great news. I hope your trees flower well this spring and set their first crop.
Hi Greg- I love your stuff! It has been extremely helpful being a first time avocado grower. I bought a Reed last summer and planted it in the corner of my yard just before the heatwave. Despite my poor choice of planting time the tree seems to have done quite well
A couple things- I’ve been using the job’s organic citrus and avocado fertilizer from Lowe’s- any insight on its quality? My reed seemed to react well to it but I’m confused on how often I should fertilize? Some sources say spring, summer and early fall while others say only once per year.
I also took your advice on the mulch and will now look for organic wood chips from a local trimmer- thanks!
Lastly- I bought a small bacon avocado tree to cross pollinate the reed. It’s still in its 15 gallon pot that I’ve placed about 5 feet from my reed- is that a good/perhaps “best” cross pollinator or should there be another I should be looking for?
Thank you for your help and keep up the good work!
Ps- I’d love to come see your property! I live in Long Beach and am completely fascinated with avocado growing now! Let me know if you’re up to it!
Hi Vincent,
Thanks for the great comments. I saw the Jobe’s Fertilizer Spikes for Fruit and Citrus at Lowe’s the other day. If this is what you’ve used, I’d hesitate to continue using it. The first thing that jumped out at me was that the analysis on the label says the source of potassium is potassium chloride. Avocados are very sensitive to chloride, and there’s already more than the trees can handle in the irrigation water we use in Southern California.
I’d hold off on any further fertilization until the tree shows a need, especially if you add some wood chips and/or compost under the tree sometime soon.
The good news is that Reed trees fruit very well without any B-type avocado tree nearby. For example, my Reed fruits well and the closest B is 250 feet away.
To most optimally use that Bacon as a pollenizer, place it so the branches are just touching the Reed. You want the bees to consider them as a single tree, which makes them more likely to visit the flowers of both trees at one time, on a single feeding flight.
Bacon does flower earlier than Reed, however. So it’s not the ideal Reed pollenizer. But don’t sweat that. Reed has no practical need for a B pollenizer in order to set loads of fruit. (Farmers who grow Reeds never bother to incorporate B varieties in their orchards.)
That being said, in my yard the only B-type avocado that still has a lot of flowers through May and even into June when Reed peaks in bloom is Fuerte. Fuerte has a very long flowering season. So it’s at least a potentially good pollenizer for Reed.
I’ve been thinking of inviting some people over to see my yard. I imagine it makes readers curious as to what the whole thing really looks like since there are many glimpses in photos here and there. It’s likely to disappoint, I fear. Still, maybe we can do a little tour day. I’ll talk it over with my wife and get back to you about it either via email or through a post on the website here.
Anyway, glad to hear you’ve caught the avocado bug. Unfortunately, it seems there’s no cure.
Hi Greg! If you get the green light from your wife to do a tour of your trees and property, please consider me. I live in inland oceanside and pretty new to avocado growing (3 years) and would love to learn and see what you have done and hopefully I can implement your successful processes in my yard! Thanks for this consideration.
Hi Rich,
Got it. That sounds like such a fun idea. I hope we can make it happen soon.
Hi Greg. I was wondering if you could tell me what I’m doing wrong with my avocado tree. The skins are very thin and the avocado, although a fairly good size, gets mushy on the bottom 3rd yet still hard on the upper 3rd of the avocados. Our tree is maybe 5 years old now, it has given us avocados for 3 years yet we haven’t really been able to eat them yet. The first year I picked them too soon. The 2nd year, the heat got to them, the 3rd year which was last year the heat also got to them but 3 survived. They are the mushy ones and the bottoms have a dark spot on them. I forgot what type of avocado they are but look so much like Hass and they are as long as my hand. Thanks if you can help me figure out what to do.
Hi Debbie,
I’d really like to see a photo of this fruit, as well as the tree. That would clue me in to a lot of what you are experiencing.
Hi Greg,
I’ve just planted a 15 gallon fuerte at my new house. I’ve followed your watering and mulching tips. Some of the lower leaves are a nice deep green and some of the upper leaves are a pale green/yellow. How soon should I apply a nitrogen fertilizer and how fast could I expect all the leaves to turn that nice deep green color?
Thanks!
Hi Eric,
Good questions. Avocado leaves only turn a deep green once they’re mature. Younger leaves are more of a lime green color, and new leaves are even reddish. So your tree sounds like it looks as it should, with the lower leaves being a deeper green. It doesn’t sound like it is in need of any fertilization now.
I think I put too much fertilizer around my avacado tree. It was nice and green two days ago and now the top leaves are dark and flimsy looking. Please help! I had also added a small bag of sand around the top to keep bugs out of it.
Hi Ann,
What fertilizer did you use? Are the top leaves reddish or brown or black?
Does this info apply to orange trees? Is mulch enough for them too?
Hi Greg,
I have read many of your posts, and each one contains great information.
One question that I have, that I haven’t been able to find elsewhere on the internet, is what will happen if I over fertilize my tree?
I have a Carmen-Hass, and was grafted about 8 months ago, so it’s only 2.5 ft tall. It’s in a 30-inch box, with peat moss, sand and pumice stone as the medium, so extremely fast draining. I have it on a bubbler that gives it 1 gallon a day, and once a week I like to soak the whole box since the bubbler just gets the base of the plant.
It’s putting on new flush of growth and was growing really well. I fertilized it on Friday, 5 days ago, with organic citrus fertilizer and blood meal, this time with an extra dose of blood meal. I noticed yesterday, some of the new leaves were falling off. If I touch any of the new leaves, the new leaves kinda just fall off. The mature leaves are still on there strong when I give them little tug.
Do you think this type of leaf drop is due to over fertilization? It’s the only thing that’s changed since I’ve had this plant, and I’ve had it since March. I’m thinking about flushing the box to leach the fertilizers…or if I should just wait it out.
Thanks in advance,
Hi Renee,
That’s an interesting question, and I can’t say I have a good answer. Did the leaf drop by chance come a few days after a hot spell? Do the leaves show any browning on their edges?
I occasionally notice new leaves dropping on very young trees but it never seems related to fertilization, and they usually have another flush come along before too long. If the mature leaves look good, you can probably wait out whatever is going on.
Thank you for this. I believe my Avocados are having root problems from water. I did a custom soil mix for them that is sandy loam with compost and mulch mixed in, but i seem to consistently lose them after transplanting (i’m forced to grow in containers here). I plant a seed, and the tree has beautiful dark leaves for months and months, but the second it gets too big for its container, even though i’m moving it to the same soil type as before, and i’m not dislodging any roots when i move it, the leaves turn a pale green and i have never had one successfully recover from it. I’ve changed nothing about their care/environment other than a larger container. What are my options here? I’m less concerned by fruit, and more love them as large shade trees, but I also feel bad when I screw up and kill something, even by accident.
This past early spring I experienced chlorosis and followed your suggestion to apply a leaf and soil treatment (iron & zinc) for my 7′ reed. It was corrected and is now close to 9′ and all the leaves look great. Do I need to follow up with another application of iron & zinc even if the leaves look OK? The tree was planted three years ago, has 20 orange size avocados, and a 6″ mulch all the way around the tree. We have clay soil.
Hi Ron,
Great to hear that your Reed is looking good and growing well. As long as the leaves look fine, I would not apply anything further. It’s quite possible that you’ll never need to apply anything again. The mulch might be helping a lot as it breaks down now. Just wait and see. You now know what to do if the chlorosis reappears.
Hi Greg,
To follow up on my comment on fertilizer in your bacon avocado post, The soil I planted my avocado is not fertile at all but it is well drained. I had a lab do a soil analysis in November and the result come back with nitrogen extremely low. I calculated the amount of nitrogen I used on my avocado tree is about 0.1 lbs which way below the 1 lbs of nitrogen recommended. On ucavo.ucr.edu website, it said for a young tree, the amount of nitrogen need per year is 0.5 lbs to 1 lbs. Do you think this is correct? If it is then 1 lbs of nitrogen from an organic source is a lot of fertilizer.
On my tree right now, I can see the effect of low nitrogen. Leaves are turning yellow and very little foliage growth.
Hi James,
Don’t expect growth on avocados right now. Some trees might be growing a little bit, but most will not grow much until late winter or early spring. Late fall and early winter is a quiescent season for avocados in Southern California, generally.
If your leaves are turning yellow, first make sure that the tree’s roots are not in soggy soil. If the roots are kept too wet constantly, there is no hope.
One thing that cannot hurt is to apply a few inches of compost to the surface under your tree. Doing this now will allow the winter rains to leach salts from it to a degree, as well as to help incorporate it into the soil below somewhat. Especially come spring, it will be eaten by microbes and other small soil-dwelling organisms like earthworms and made available to the roots of your tree as needed.
Hey Greg,
It is me again. First thx for the answer, but I am still wondering about when and how I should apply the manure. Is it okay if I apply it in December? Should the manure be injected in the soil or should be applied on the surface, or maybe directly under mulch?
Thx in advance for your answers.
December is a good time to apply manure because upcoming winter rain will leach salts.
On such young trees as yours (7 months in the ground), I would put only an inch or two down.
Put it above where you think the tree roots are, which is mostly wherever your irrigation water lands. You can put it on top of the mulch or lightly mix it into the mulch. But don’t bother trying to get it under the mulch, which runs the risk of burning roots with hot manure or damaging roots while scraping away the mulch.
Hi Greg, I’ve got a bunch of Hass trees planted in June and they did real well through the fall with a lot of new growth. The trees that had the most new growth to older leaf ratio Coming in to winter are now quite yellow, even after fertilizing a small amount every other watering per instructions from a UC study. I’d love to send you a picture somehow and see what you think.
Hi Casey,
Wonder if the trees will green up again when they start growing in spring. I’ve had some trees do that. It can be related to cold weather/soil and the particular rootstock; it’s possible that soil moisture is too high consistently or there’s a nutrient or pH problem in the soil.
Anyway, with those kinds of situations I take a wait-and-see approach because they often correct themselves as the seasons change. If new growth in spring is still not looking right, then I’d guess the problem is in the soil/rootstock interaction. There are some rootstocks that are sensitive to certain soil conditions and will make the scion/canopy chlorotic. Get back to me in spring if the problem remains, and I’ll tell you what I know about how to deal with it from there.
Are worms good to have in the soil? I just placed a few pieces of sod between 2 of my avocados for 48 hours and I have over 100 hundred of these worms. Didn’t see any when I laid them down, but here they are. https://ibb.co/GpTs3Kr
Should I get rid of them before the travel to the avocados on a rainy or foggy day. My dirt is clay like in San Pedro, CA.
Hi Paul,
Worms are useful, as they’ll make tunnels which will help water infiltrate your clay soil, and they’ll poop. People pay a lot of money for bags of worm castings to use as fertilizer. So definitely leave them be.
P.S. I also use worms as an indicator of soil moisture under my trees. If you scrape away the mulch under a tree and find worms in the top few inches of soil, then it’s still moist and you probably don’t need to water yet. But if there are no worms, then they’ve probably gone deeper or somewhere else where the soil is more moist and hospitable so it’s probably time to water.
Hi Greg,
We only have a few avocado trees but I have lots of mulch from shredding up some eucalyptus trees. Is that type of mulch okay with avos?
For sure, Charlie. I have used lots of eucalyptus wood chips under my avocado trees in the past. (And I love the way eucalyptus chips smell as they decomposes.)
Hi Greg,
Thank you for the useful information. We live in Florida, my Avacado tree is almost 9 years old. Only once, the yield was around 80 Fruits ( shared with my friends) and from then on every year, it gives only two or three fruits. This year it bloomed so many flowers but not a single fruit. I fertilized with citrus/Avacado fertilizer, in August and in February. It had bloomed so many flowers but all fell off. It is starting to grow with new branches. What has caused for flowers to fall off ? Please guide me how to get more fruits every year.
Thank you
Sree
Hi Sree,
I don’t know much about the quirks of avocado pollination in Florida conditions, but I’d suspect that a second avocado variety with an opposite flower type could help. A very knowledgeable grower in Homestead has said that he finds lots of extra production when his avocado trees get this cross pollination.
Greg- I’ve been reading your posts for the last several years and they’ve been excellent. I live in the Oakland Hills in Northern California and have several avocado trees. I have 3 year old fuerte tree that has a ton of flowers and great bee activity. Since I’ve owned it, the leaves are droopy and more greenish yellow than dark green (like my 13 year old Haas). I’m not sure if it is a soil, root rot or water issue. There are 4 other trees within 10 feet that don’t have this problem. Could I send you pictures of the tree and soil? I’ve read all your posts (I think) on these topics.
Also, do most trees kind of get droopy when flowering? My bacon and reed trees also show a little of this at the top. It’s been warm so I have watered a little more in the last couple of weeks but the soil doesn’t feel very damp. Would love your thoughts to increase the odds of a good fruit set! Many thanks.
Hi Lindsay,
Thanks. Fuerte leaves especially droop down when flowering or growing new leaves, as at this time of year. So that symptom is not likely a problem.
It is also possible that the light green leaves is not a problem, as long as it is only happening now and not throughout the year. When new avocado leaves emerge they are reddish, but then they become light green, like a lime green, and only after a month or two do they gain their deep green color. So this time of year, leaves on avocado trees have a diverse appearance in terms of color and shape, and often people think their trees are sick but it’s just the season. I think of June or July as being the best time of year to look at an avocado tree’s leaves and easily judge its health, that is, if an avocado tree doesn’t look “normal” at that time then it’s surely not.
Hi Greg,
I rented a trailer and went to a soil yard and bought partially composted shredded trees and green waste. I calculated how much I needed for 3-4 inches but I think they gave me way more than I asked for, and I ended up with 6-7 inches of mulch in my citrus and avocado orchard. I read somewhere that this could be a problem. What is you experience with this? Is this too much? It would;d be a pain to remove 3-4 inches but I will if It will cause problems down the road as my trees are quite healthy. I noticed it is quite hot at the surface of the ground when I dig down to the actual soil from the composting effect of all the mulch.
As always, thanks in advance.
Chris
Hi Chris,
I wouldn’t worry about it. Just don’t cone it up at the base of the trunk. I’ve added around 12 inches deep before with no apparent problem.
I bet the 6-7 inches becomes 3-4 inches, max, by the end of the summer, and if the mulch/soil interface gets a little too hot momentarily, then the roots will perhaps burn back only to grow and return to the surface with glee once it cools. I’m always building small compost piles beside my trees, and the mass of white avocado roots to be found there after a couple months tells me that the trees love it.
Great, that was what I was thinking and hoping to hear, thanks Greg!
Great information for Avocados. I live on a hillside lot in East County San Diego and I have 4 Avocados (3 Hass and 1 Zutano. I Want to add two additional Hass trees and the location is pretty steep. How large should the planting well around the tree need to be? The location is such that I can only get about a 2-3ft diameter well around the trees without doing major excavation. I have my trees mulched so as to fertilizer, if the trees need fertilizer can I just spread the fertilizer on the top of the mulch?
Hi Gerry,
Thanks. You shouldn’t need to make a well, or watering basin, any wider than 2-3 feet in diameter unless you’re planting very big trees. The goals with a watering basin are that it holds the water in the right place (above the tree’s rootball) and that it holds enough water such that you don’t have to fill it up too often (and this is partly determined by how high the rim is, not just how wide the basin is).
I don’t know what type of fertilizer you’re using, but most likely you can just spread it on top of the mulch and then water it in.
Hi Greg,
I have been trying to grow Hass and Fuerte for the past couple of years, without luck. I live in N. California. My trees are on the north side of my yard and get direct sun for ~8 hours. I have created a 2-foot mound then planted the trees in the mound, added ~4 inch local mulch, and put a “shade” cloth above and on the west side of each tree to cut down the intense sun on the young trees. At first planting the leaves on both turned brown ~1 week afterwards, died, then a tremendous push of new growth. After this, one tree just started to brown at the tips followed by the leaves – it’s a goner. The other is hanging in there. A third plant (Fuerte) which is in a 15 gallon pot, pushes new growth and the older leaves turn brown and die, without fail. I have 4th plant (Hass) in a 15 gallon pot underneath mature alders (mostly “broken” sunlight) and appears to be doing great. Any advice you can provide will be greatly appreciated as I have searched a lot online regarding potential causes, which I can sum up as follows: Too much/too little water, too much /too little fertilizer, etc… If you think pictures would help, please let me know. Thank you in advance!
Hi William,
Photos would be great if you could post a link to some. Your Hass in a pot that is doing well in some shade makes me suspect too little watering is the problem with the others, but that’s just a suspicion.
Hi Greg,
Thank you for the quick reply. I have recently been using a moisture sensor to assess when to water the trees. It’s possible it’s misleading me. The Fuerte was “resurrected” from last year’s attempt by placing it into the pot at the beginning of this year. Here’s the link to images:
https://photos.app.goo.gl/eL7KqgXWgzm4BWRU8
I look forward to your insights.
Hi William,
Thanks for the photos.
Tell me a bit about your dirt in that part of your yard. If you dig a hole a foot wide and deep and fill it with water, how long does it take for the water to drain out of the bottom?
Hi Greg,
The native soil is hard and compacted, thus the reason I built the mounds. The soil within the mound (~4ft diam and ~4ft deep) is a mix of native soil, ~10% amendments, and ~20% of perlite. The part of the mound below grade was dug out, with a “bowl” shaped bottom. At the bottom, I put in a “French” drain to allow the water to drain out toward the fence, where there is a steep slope.
Drain times: Native soil 20 minutes, soil in center of mound 4.5 minutes.
I look forward to your response.
Hi William,
I suspect too little water, or water too infrequently (which is more often the problem with young trees or trees in pots). My reasons are that your drainage times are super fast, your trees showed browning leaves only a week after planting, and your trees in pots have the same symptoms as the those in the ground — besides the Hass in a pot in the shade, which would be needing less water because it’s in some shade.
Hi Greg,
Thank you for the response. A few more questions: 1) How best to assess the right level of moisture? As I was previously told that too much and too frequent water will rot the roots. 2) If there is an optimal drainage rate, what would it be? 3) Is the native drainage rate too long and bad for growing Avocados?
Thanks again!
Hi William,
These are very good and important questions. There is no right level of moisture, but there is a range of moisture levels that you must stay within. Too low and the roots can’t extract water from the soil. Too high for too long and the roots begin to die and are vulnerable to diseases like root rot. How do you know the soil is within the proper range? Much depends on your method of watering. Can I ask if you’re using a hose, sprinkler, drip, other?
There’s not an exact optimal drainage rate, but it’s convenient to have fast drainage — like under an hour — because then you don’t need to worry about planting on flat ground and getting a lot of rain in winter. The slower the drainage, the more careful you have to be about planting above grade and watering too much too often.
Hi Greg,
Thank you for the information.
Right now my method of watering is hand watering using a water pitcher that holds ~2 gallons. For the potted plants, I water until the water seeps out the bottom. For the in-ground plants, I water 2-ft around the perimeter inward using 1 to 2 pitchers. The frequency of watering is every 2 to 4 days for the in ground and 1 to 3 days for the potted. I use my moisture probe to assess moisture level along with leaf droop to determine when to water. If there is a better way to determine if the soil is too dry/wet, please let me know.
Hi William,
What you’re doing sounds in the ballpark of what the trees probably need. I guess it’s possible that the mix in the pots and the soil in the mound are so fast draining that you need to water a bit more frequently though — not necessarily with more volume. Essentially, split your water volume into daily or every-other-day irrigations and see if the trees respond well. That is what I would try.
I would also use my hands to gauge the moisture instead of a probe. I don’t find the probes to be as reliable as my hands. With the pots, I’d also pick them up to feel the weight. Water is very heavy, and it’s pretty clear when a pot has a lot or a little moisture in it.
Hi Greg,
Thank you very much for your insightful responses.
I will proceed as you suggest, and let you know down the road how my avocados respond.
Greg,
Unfortunately, my inground Hass did not survive, but my potted plant under the old-growth alder canopy did. In the latter part of the summer we had many days of extreme heat (~110 F) and the inground just could not keep up even with the shade cloth. The potted plant did ok. I am still puzzled why the inground avocados are not surviving. A thought is that the property-line redwood fence that is ~ 5 feet away from the trees is “trapping” and radiating too much heat for the trees, even with my shade cloth for the direct sunlight. Thoughts? It is now February and I would like to try one more season with avocados. I am thinking of getting > 15 gallon plants to see if they will be more tolerant/stable than the smaller ones I have tried. Any additional advice would be much appreciated prior to my moving forward. Thank you.
Hi William,
Sorry to hear it. Have you dug around next to the inground avocados to see if there are roots other than avocado roots? It might be that the Alder or Redwood trees are sucking the baby avocado rootballs dry. I’ve dealt with this near Live Oaks and Camphor and other large trees near baby avocados.
Your idea of planting a 15 gallon is a good one. In spots in my yard where oaks and sumacs steal water from my newly planted avocados, I find that the bigger trees (at planting time) generally do better than the smaller trees. That is not always the case, but it usually is.
Mr Greg,
I have planted some Hass avocado in Morocco. All trees are in perfect condition and this is the first growing season. All foliage is thick and healthy green and the average tree is about 1.7 meter in height and takes a canopy of aprox 2 m2 per tree.
My question is about winter fertigation…The trees are on sandy soil and i am not sure if i should stop nitrogen application in the winter. Average winter temperature in Celcius in my location is aprox ..15 to 20 Daytime and 2 to 10 nightime.
Can you give any guidance?
Thanks,
Patrick
Hi Patrick,
I haven’t been to Morocco but from what I read it sounds like your conditions are similar to ours in California: http://www.avocadosource.com/CAS_Yearbooks/CAS_49_1965/CAS_1965_PG_049-051.pdf
The common practice with fertigation here is to cease in winter since the avocado trees usually go into quiescence. Also, little irrigation is usually necessary since this is our rainy season. Here is a chart on fertigation for California growers that you might find useful: http://ceventura.ucanr.edu/Com_Ag/Subtropical/Avocado_Handbook/Fertilization/Nitrogen_Application_with_Micro-irrigation_/
Hi Greg, I have a Fuerte tree that my dad planted over 60 years ago. I live in the San Gabriel Valley of Southern CA and over that last two years the leaves have been very light in color and not as many leaves. The fruit also yellowing in spots. I have been watering and fertilizing with the same schedule over the years. Watering with a sprinkler around the canopy and using citrus/avocado food. The fruit this year is the smallest that we have ever had and lots of dead branches. I can send photos. I hope I can save the tree.
Hi Donald,
Your description sounds similar to overwatering and/or root rot symptoms. See more about this here: https://www2.ipm.ucanr.edu/agriculture/avocado/phytophthora-root-rot/
The reason your fruit is yellowing in spots might be because of the lack of foliage to protect it from the sun; in other words, the yellow spots on the fruit might be from sunburn. If the spots are on the upper and south-facing sides of fruit, then sunburn is very likely the cause.
Hi Greg, thanks for your response. I will check the roots this weekend. I do have mulch around the canopy.
Ooooh, maybe you’ll be able to predict what the future holds for our avocado tree! We live in the Mission, in San Francisco. The previous owners planted an avocado tree maybe 30 years ago. The tree is gigantic, maybe 25 feet tall, which is impractical but it’s pretty and provides privacy. The tree has full southern exposure. According to the previous owners, it never fruited. Our neighbors planted an avocado tree last year and this year we got some tiny fruit- not even as big as limes. The soil is clay, and since the yard is small, we can’t mulch the entire area underneath it. As I write this, the tree is almost flowering. It doesn’t seem to be a Haas (the tiny fruit has smooth skin). Any thoughts? We’d love to get some full size avocados if it’s possible. I’m so thrilled to have found your page! Thank you!
Hi Renee,
What you describe makes me wonder if your tree is a Mexicola. Have a look at photos of Mexicola here: https://gregalder.com/yardposts/avocado-varieties-for-year-round-harvest/
And here: http://ucavo.ucr.edu/AvocadoVarieties/VarietyFrame.html
Could be. As of now, the fruit grows to half the size of a lime. And there’s very little of it- maybe 25 avocados, only on the south facing side of the tree. So I can’t tell what variety it is, unless I’m missing something!
Hi Renee,
Have you eaten one of the avocados?
I live in florida and my avocado is about 6 yrs old. It has never produced an avocado. It put some blooms last year but they did not hold on the tree. I want to know what fertilizer to use and any other help you may provide me. Thank you/
Hi Ruby,
I’ve never known fertilizer to make the difference between an avocado tree having fruit or no fruit. You might look into other explanations. For example, is it a seedling tree or is it grafted?