There are some avocado trees in Southern California that survive on rainfall alone. Some that I know were once part of old groves while others appear to have grown as wild seedlings from the beginning. Have they tapped into an underground water source? Are they on a particularly drought tolerant rootstock?
Here’s a video of one such feral tree that I’ve been visiting for many years. As you’ll see, it’s having a great bloom this year despite the low rainfall we had last winter. In fact, it’s blooming better than some of the trees that I pamper with irrigation in my yard!
What lessons can we learn from this tree?
One is that we might be overwatering some old trees, especially if we water them much during winter.
Two is that allowing weeds to grow as a living mulch beneath an old avocado tree is clearly not a big problem.
This tree also makes me think of the old avocado trees in residential settings throughout California that are declining and that it seems more likely that the decline is related to changes around the tree than it is to neglect. The changes I’m thinking of (and that I’ve seen recently) include putting in a new pool near an old avocado tree, or building a patio under and around an old avocado tree. Both such changes kill many roots and compact soil over others.
This tree also makes me think of the leaf burn phenomenon that many of us see on our avocado trees in Southern California. Did you notice in the video that this feral tree has almost no leaf burn? (Though I have to note that I have seen it with more leaf burn in past years.) This lends credence to the explanation that it is mainly chloride buildup in the leaves that causes the burned tips. Chloride levels are far higher in our imported irrigation water than they are in rainfall. This tree only receives rainfall.
There must be more. What lessons am I not seeing?
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Thanks for making and sharing this post/video, Greg. I attended your lecture (virtually) re: avocados with the OC RFG folks – very informative, thanks for that invite! Regarding this “rogue” avocado tree growing wild, I love this story. I often reflect about the tenuous nature of the veggies I grow in containers in our backyard here in Pasadena, where it gets VERY hot over the summertime. Of course, once established a large tree like an avocado has a giant root structure and has advantages over small plants such as most vegetable plants. Nevertheless, it’s inspiring to see this avocado tree soldiering on all on its own, in the mountains no less!
Hi Greg,
Do you know what species of tree this is?
Have you thought about planting some seeds from this tree?
I recently read an article about an Indian tribe in the southwest that is growing corn in the desert.
Maybe this tree is the beginning of a avacado that needs less water.
Hi Bryan,
It might be a Fuerte: the leaves, flowers, and fruit all align with Fuerte characteristics. I haven’t thought about seeds, but I have thought about cloning the rootstock. And I have taken scions and grafted them into trees in my yard. Wouldn’t it be great to be able to grow avocados on less water?!
So when one of my neighbors dug her pool she hit water table at 11 feet and we are on a big hillside area of Laguna hills. These old avocado trees must hit water table with their old roots. Many old neighbors also said we have a underground river as some folks can’t seem to get away from too wet ( I don’t have this problem sad to say) I have to amend my granite/clay soil and water it too!!!
Hi Tina,
I wonder if that’s what’s happening with this tree. Wish I could somehow see through the dirt to where underground water is!
There might be a way– https://www.youtube.com/watch?v=DS9XuxrglVI
I just found this–
https://www.americangeosciences.org/critical-issues/maps/interactive-map-groundwater-levels-and-subsidence-california
Another thing to consider just like in Temecula they have their “fog” sort of speak from the ocean that comes rolling in to hydrate their grapes. I wonder if this stream of air is similar to this tree. Besides the possibility of water underground. Talk to the growers from this area of grapes they will tell you why they can grow them without a lot of water due to this area of cooler wet air that blows in.
Hi Tina,
It is true that this area is part of the L.A. Basin which collects a marine layer (and smog). That can only help.
Greg, I’m not so sure about your lead burn comment. My Fuerte, Reed, Kona Sharwil get about the same amount of sunburn. Haas gets slightly more, but Wurtz gets almost 0.
Same soil, same water, same irrigation line i.e. watering frequently. All of the above are at the top of the slope but Wurtz which is slightly below.
I was surprised that Reed got quite a bit of lead ends burn despite being advertised as resistant.
Hi Alex,
These things are complicated! It is very difficult to distinguish what is causing leaf burn symptoms in a setting like yours (or mine), where we have different varieties on different (often unknown, seedling) rootstocks that are higher or lower on a slope (therefore possibly getting slightly more or less water even if on the same line) and that are closer or farther away from other established plants which compete with the trees with their roots.
Just one example from my yard relates to the Sharwil variety. I’ve now grown eight different Sharwil trees or grafts onto other trees in my yard, no two of which have performed exactly the same. In fact, today I’ve got one Sharwil tree that looks terrible with a lot of leaf burn while I’ve got two others that have almost zero leaf burn. More than that, the tree with terrible leaf burn has an abundance of bloom whereas the trees with perfect foliage have no flowers.
What’s the explanation? I don’t know. I have some hunches, but there are so many factors that contribute to these phenomena that I rarely feel very confident in a diagnosis.
Same goes for the idea I mentioned above about the contribution of chloride to leaf burn. That contribution has been shown clearly since way back in 50s or even earlier. See here, for example: http://avocadosource.com/Journals/CA/CA_1951_V5_N12_PG_7.pdf
But inadequate water also induces leaf burn. So my suspicion is that when the feral tree in the video has lots of leaf burn some years it is because of inadequate water (rainfall).
Back to my Sharwil with bad leaf burn. It is next to a Reed with almost zero leaf burn. Like your trees, these two are on the same irrigation line in the same soil etc. What’s making the difference? My only guess is that the Sharwil rootstock (an unknown seedling, I think I actually used Hass but can’t recall for sure) is contributing, and the mature Reed is sucking away a lot of the water I apply to the younger, smaller Sharwil. But it’s only a guess!
Yeah, all these factors are tricky to control for or even account for. E.g., the article you’ve referenced mentioned chloride whereas in many areas it’s no longer used. The water treatment plants more often than not use chloramine, as it’s the case in my area. I’m not sure that the chloride research should necessary transfer well to chloramine.
To your point the soil 15 ft apart and downhill could differ significantly. Not to mention the other effects you mentioned.
With that said, I think the case studies you do are very valuable for staging future experiments or analysis of the compiled data.
Thanks.
a neighbor has many older avocado trees that produce crops. she’s not sure of the type because there were there when she bought the house. she says she almost never waters her avocados. they are all beautiful and full and healthy with no leaf burn.
Hi JB,
What a nice house to have bought. I envy your neighbor. I’ve seen such old trees that never get deliberately watered, and their root systems have grown so broad over the years that they pull sufficient water from various other irrigated plantings nearby, often even over fences and walls in the yards of neighbors.
Hi Greg,
Speaking of trees that soldier on with little water, what is your take on the drought conditions for the future of avocados in southern California, specifically in the Temecula area?
This years heat has forced strip picking to salvage the crop.
Hi Jim,
I don’t think I’m qualified to give real insight here, but I will share what an old timer told me about a dozen years ago when I was considering going into commercial farming avocados in San Diego County. He said to forget about it unless I was on land with a well that produced high quality water in high volume. (What’s “high” exactly? I don’t know.) His opinion might have changed a bit since today we have some better rootstocks available to handle salty water though.
Hi Greg,
I have a feral avocado tree to share with you. I enjoyed your post on this subject and it me looking for feral trees in my own area. There is a large 50-60 ft tall specimen in an “open space” area in San Juan Capistrano. As far as I know the area used to be an orange grove ( There is an orange tree growing from the base of the avocado). The tree has no irrigation. I have seen it flower but have yet to see any fruit. I have pictures if you are interested maybe you can identify.
Thanks,
Chris
Hi Chris,
I’d love to see photos of the tree and maybe visit it sometime. Reminds me of an old tree I’ve read about in SJC called the Williams avocado tree. Don’t know if it is still alive though: https://www.avocadosource.com/CAS_Yearbooks/CAS_70_1986/CAS_1986_PG_103-105.pdf
Salt burn sometimes from tap water. Much water from Northern California Aqueduct can have contact with Bay Ocean water.