Winn Sawyer

Jay Angler wrote:Have you ever tried adding biochar to your soil mix? If so, did you notice any benefit? I posted more as a possible  approach to improve our success rate, but gardening rarely offers guarantees. There's lots of garden advice out there that hasn't got a hope in my ecosystem!

I have not, but my soil generally seems pretty good for most things, other than being slightly acid and slightly low in nitrogen. I haven't had any need to modify other than bit of lime for some things (not avocados), and occasional fish emulsion + generous mulching with wood chips for everything.

Jay Angler wrote:Cool tidbit from a book I've been reading!
The book quotes Doug Pow in Australia:
"Avocado trees come from a volcanic andosol, extremely new soil derived from volcanic ash, different from any soil in the world," he said. "We are trying to chemically get the soil similar to that which they evolved in, and biochar assists that."
"At 5% biochar the leaf area has doubled."

From: Burn Using Fire to Cool the Earth by Albert Bates and Kathleen Draper Pgs 111-112 There are a few more details

I'd be curious to see the source for that claim about the soil where avocados evolved. Most of the papers I've read on that topic proposed that the Mexican highlands around Nuevo Leon are the original location of the species before it was domesticated many thousands of years ago. According to the attached soil map of Mexico, that area (which I've circled in red) is not listed as volcanic andosol.

A friend of mine started a whole pile of Avocados growing in a raised bed she had veggies growing it. I just spent the afternoon transplanting over 20 babies into #10 pots. Many of them had taproots at least 6" long. It was a shame to have to bend them. This is why it can be so much better to start tree seeds right in their forever homes, but it is just too hard to give them any protection that way. Not sure what this winter will be like, but I will do my best to keep them alive!

This is why I start mine in 14" deepots, and even in those the roots usually reach the bottom in a few months from sprouting. Starting them in their final location is definitely best if you plan to protect them with a heated cover for their first winter, but the problem with doing that is most Mexican race (hardier) types ripen from August to now in the northern hemisphere, and the seeds will likely not survive the winter outdoors in cold locations, and may only barely germinate before then, so they need to be started indoors. The other races of avocado ripen from late winter thru the summer, so those can at least be germinated before winter.

Steven Feil wrote:Has anyone tried DEHYDRATING the fruit. This seems like a natural to keep the fruit around longer. If there is still too much maybe freeze it and then dehydrate?

Not recommended, you're much more likely to get the horrible digestive response. See this post:

https://permies.com/t/50190/Intolerance-Pawpaw-Fruit#594845

Mike Guye wrote:
I just want to check language-use here. Winn, when you use the term  ‘dormant buds’  do you mean the botanical sense of the word, i.e. inconspicuous buds that normally only open following a very stressful event, e.g. complete defoliation, or do you mean normal buds that are ‘overwintering’ ?

This is a good question! I'm referring to all the buds on the tree that are not actively growing. As you correctly pointed out, the flowers generally only form on the terminal buds of the previous flush on each branch. However, I have noticed that sometimes a long-dormant bud on older wood under the canopy will grow just one or two leaves in summer, and that "terminal" bud will often flower the next year even though there was no clear stem extending from the branch.

If you have not seen it previously (I may have sent it to you?), I highly recommend this publication from the agriculture ministry of Western Australia. Here are some excerpts:

The first aspect is to consider what triggers flower initiation. The general consensus is that a period of low temperature (below 20°C) and short day length (less than 10 hours) is required to initiate the transition from vegetative bud to floral bud (Buttrose and Alexander 1978, Nevin and Lovatt 1990, Salazar-Garcia et al. 2006).

The term ‘irreversible commitment to flowering’ is used to describe the time when the apical bud becomes committed to reproductive growth. Generally, this is achieved after the accumulation of about 28 days of conditions suitable for flower initiation (Salazar-Garcia and Lovatt 2002, Salazar-Garcia et al. 2006).

The statement of ‘irreversible commitment to flowering’ can be a little misleading. It implies that once achieved, the bud will continue to develop as a floral bud regardless of conditions. However, certain events can arrest further development of the floral bud. For example, a moderate frost event on 17 June 2006 resulted in what appeared to be significant damage to buds (Figure 5), even on shoots with only minor leaf burn.

Based on the requirement of 28 days below 20°C and the temperature conditions normally experienced in the South-West, it could be anticipated that irreversible commitment to flowering had occurred prior to the frost. However, after the frost event the majority of buds that would have been expected to flower actually developed into vegetative growth in the following spring, with generally only a few weak late flowers. Therefore it would seem that the period of extreme cold temperature had either damaged the developing flowers or almost totally inhibited their further development while promoting vegetative growth.

Avocado flowers are borne on new season growth, that is, shoots produced during the previous season’s vegetative flush. Therefore, growth of shoots is required to produce buds that can develop into flowers. In the South-West of Western Australia, three vegetative flushes are normally observed – a spring flush, summer flush and autumn flush, similar to New Zealand (Dixon et al. 2008).

Flowers can develop on any of the flushes, but the spring flush reportedly provides the greatest contribution in Mexico (Salazar-Garcia et al. 2006) and New Zealand (Cutting 2003). These were both in minimally irrigated orchards that resulted in a strong spring flush — that is, a greater number of shoots produced per branch, compared to later flushes.

Salazar-Garcia et al. (1998, 2006) observed that under Californian and Mexican conditions, crop load did not have a significant impact on the number of shoots produced.  The percentage of floral to vegetative shoots produced from these shoots the following flowering period was affected in California but not in Mexico. In California, the ratio of inflorescences to vegetative shoots was significantly higher after a light crop as compared to a heavy crop. What was not reported was the length of the shoots produced or the total number of flowers produced as a result of differing crop load. However, Salazar-Garcia et al. (1998) reported that in California the return flowering after a heavy crop was less intensive than after a light crop.

Dixon et al. (2008b) estimated that a shoot producing at least six panicles gave the best initial fruit set. This was estimated to be a shoot of about 150 to 200mm long. Dixon also noted that in a heavy flowering year, there was a higher percentage of initial fruit set per inflorescence than in a light flowering year. Unfortunately, what was not reported was the total number of shoots produced in each year, to determine the impact of crop load on the total number of flowers, rather than just the impact on the individual shoots.

I should add that the precise thresholds they cite were generally for Hass specifically, so other cultivars (including seedlings of Hass) likely have different specific temperature and daylength thresholds, but they probably all follow a similar basic pattern.

Mike Guye wrote:

Winn Sawyer wrote: I'm guessing the lack of flowers was at least partly related to the amount of freeze damage, but it's interesting the least-damaged inner branches didn't put out a few flowers

My interpretation is slightly different - I think the flowering in 'Hass', observed in spring 2023, was due to environmental stress. Winter 2022/23 was more severe than last winter (e.g. 26 vs 12 frost days), and was reflected by the the more severe visible symptoms of winter-injury (95% defoliation) at the time.  I think this severe injury triggered the plant to flower, though it produced only three small inflorescences.  

Going into 'reproductive mode' is a common response of plants exposed to unusually extreme  environmental conditions for the plant species concerned, whether that's caused by  temperature, drought, a severe attack by insect pests, etc.  Though 'Hass' did suffer significant injury last winter, it was probably not enough to trigger flowering in spring 2024 - I may have to wait a few more years until the tree is naturally mature enough for flowering to occur on a regular basis ...

That does make some sense, but the problem with that theory is that the almost invisible dormant buds "decide" whether they are going to be flowers when the flush that created those buds is finishing the previous growth cycle in fall. No new flower buds can form on new growth in spring, they only come from the dormant buds that overwintered. So usually you cannot get flowers at all if the existing dormant buds on growing tips are all damaged, only vegetative buds will form adventitiously on older wood.

Your tree is larger than many seedlings I've seen flowering. One of my own seed-grown trees that's got a trunk half that diameter flowered for the first time this year (no fruit set). Once an avocado tree is "mature" (has flowered once) it typically remains that way and does not revert to a pubescent stage, though many do fall into biennial bearing patterns.

Mike Guye wrote:

Peter Entwistle wrote: Wow, the Hass seedling has really thickened up nicely now, Mike!

Yes, around a 2 cm increase in mean trunk diameter at ground-level, compared to last year - it's very vigorous. Next spring, this tree will need to be pruned hard to control its size & shape, but that wont prevent its continued increase in trunk girth.

I like to do most of my pruning "for shape/size" right after they finish flowering and the first major fruit abscission in early summer, rather than risk removing branches earlier in spring that might have set fruit. Often only some of the branches set flowers, so it would be a shame to accidentally remove all of those.

Mike Guye wrote:This year, I've been a bit delayed in getting my UK outdoor avocado-growing blogs up-to-date. However, Hass & Fuerte have now been updated, up until August 2024 (see links below).  There may be one more update in November, focusing on growth-rates towards the end of the growing season.

Hass (7-year-old tree)...    https://imgur.com/a/5gflnlU

Fuerte (5-year-old tree)... https://imgur.com/a/0XuODou

Blogs for Bacon, Del Rio, Daughter, Joey and Wilma are in the process of being updated and will post here when done.

Those are looking great! I'm guessing the lack of flowers was at least partly related to the amount of freeze damage, but it's interesting the least-damaged inner branches didn't put out a few flowers.

This is reminding me that I should post an update on the Cascadian avocado thread to show the amount of regrowth I've gotten on my various outdoor trees.... maybe tomorrow! Need to take a bunch of photos.

Hi everyone!

Due to starting a few more seedlings than I'll be able to pot up for 2025 distribution, I've begun distributing larger numbers of smaller trees in the last few weeks. If there's anyone who's thought about joining the project, especially if you're willing to plant a large number of seedlings in the ground, please reach out!  Especially anyone in the immediate Seattle area, or within a couple hours drive of Seattle. Here's the page that summarizes what your membership will entail (ignore the part about 2024 distribution being finished):

https://www.drymifolia.org/join.php

Here's an example of the type of planting I'm looking for, this row of about a dozen trees was planted at a member's place a few weeks ago:

Ben Zumeta wrote:Grafting female scions onto your planted rootstock could also be an option. I believe Burnt Ridge sells mulberry scionwood.

This was going to be my suggestion! I've bought scions from both Fruitwood Nursery and Really Good Plants (Marta Matvienko).

Another option is to look at this list of how easily each cultivar can be rooted, and order scionwood of those cultivars easiest to root. I've successfully rooted a few cultivars of mulberry scionwood, such as Galicia from Marta.

The study didn't really make me any less dubious, since it was statistically the same as the control in almost every aspect they measured. The fact that it contains some trace amount of growth hormones does not mean it's actually good for your plants, and their study even showed it's worse for your plants in some cases (green cuttings).