The great Seattle cold-hardy avocado trial

My assistant is helping survey the trees to be distributed.

Does anyone with more avocado experience have any thoughts on what this could be? It seemed to come on suddenly in the last month, I’m not sure if it predates the freeze because I rarely look in this corner of the greenhouse, so I guess there may have been a cold pocket here? But it also doesn’t really look like freeze damage. I’m hoping it’s not a systemic infection (Verticillium perhaps? I had that suspected on another tree last year that was culled).

This is a graft of Wilma now:

And what it looked like a couple months ago:

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I wouldn’t say that I have more experience than you :slight_smile: Nevertheless, I would like to answer.
I have also discovered these brown discolourations on my Lila. This was already in autumn in combination with lots of light and temperatures around freezing point. I think that’s where it comes from. Maesy had told me that he had seen something similar on his avos.

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I’ve also seen that! But in this case it did not have lots of light (we never have that in winter), and the coldest temperature in the greenhouse was above freezing, so even if this corner was colder than where the sensor is located, it can’t have been much below freezing.

Just to clarify, even on a fully sunny day, this corner of the greenhouse does not get direct sun in winter, because of the low sun angle. So it would only get indirect/diffused light from the greenhouse panels.

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Yes, that’s really weird. The leaves of my Lila look like that (exactly like yours):

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Joey joins the “getting ready to start flowering” crew in the greenhouse:

Here’s the breakdown among all the grafts on greenhouse in-ground trees at the moment:

Variety Bud stage
Aravaipa fully dormant
Brissago fully dormant
Duke early stage flower buds swelling on both grafts
Jade flower stalks beginning to extend
Joey flower stalks beginning to extend
Linh fully dormant
Long South Gate fully dormant
Stewart early stage flower buds swelling
Teague fully dormant
Walter Hole extreme levels of flower buds have been slowly swelling all winter, stalks just beginning to extend now

EDIT: Just added links to their profiles on the project website, which includes a summary of the source of the variety and some photos of grafts in the project.

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This video in the link shows the winter behavior of three avocado trees which I bought in summer of 2022 in 5 gallon pots. They were planted in the summer of 2022 in a very open farmland in the CA Central Valley. I have a Min/Max thermometer in my shed and was surprised to see that we had 24F this winter at this particular location.

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Thank you for sharing! I hope you will share updates as they start waking up this spring. I am a little surprised at how well the Zutano looks after 24°F, but I wonder if it will self-prune more as it wakes up.

I’ve stopped using Zutano seedlings as rootstocks because both of the ones I had in the ground outside last winter failed to wake up at all last spring, and their grafts eventually died even though they appeared to survive the winter above the graft.

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So is Aravaipa a good roostock in your location?

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I only have a similarly small sample size of 3 Aravaipa seedlings that were planted out last winter, and none of them were grafted. Two of the three survived to about an inch above the soil line, while the third one re-grew briefly from the roots and died over the summer (maybe lack of water in its weakened state). So they might work for a very low graft, or where soil is mounded above the graft during any freeze, but they seem less hardy than Duke or Mexicola Grande seedlings.

This winter I also tested an own-root clone of Aravaipa, and it was badly damaged by 28°F and then appears to have been killed by the freeze this month. But maybe it’ll regrow from below ground in spring.

There are more Aravaipa seedlings distributed to members last year that I haven’t checked in about yet this winter, and another batch included with the distribution starting in a few weeks, so there will be a larger sample size in the end to say how the seedlings tend to do as a cohort.

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ok, good to know which ones are working out for you. I did see many grafted Mexicola Grande trees at my local Home Depot recently. I think I bought 2 trees (5gal) to use for my grafting demo but maybe I should just let it grow more and graft it to my larger tree to get more source for it.

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Yeah, that’s what I figured as well. I visited the tree on Christmas Eve. No fruit on the tree, we’d figured that might happen, so we began hunting for old avocados or seeds in the lawn beneath the trees.

After about 15 minutes of looking, we came up with two, partly rotten, small avo skins. They were a full skin, still taking the shape of an avocado, but they were nowhere near the size of Duke that I’ve seen in the pictures.

I ripped one open, to see if I could score on a viable seed. Inside was mostly empty and dry, but there was a little hairball around a tiny avo seed. It was hardly bigger than a quarter, kinda soft and rubbery, and the two sides were srunken, they didn’t look fully filled out to me. I tossed them both.

Might these be immature avocados?

I must say, it’s a beautiful tree:

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Definitely what it sounds like.

Thank you for posting the photo! I have never made it there to see the trees (there are two, right?) myself, so I’ve only seen them on Google Maps street view from all the way across the parking lot. You could tell they are large trees, but seeing it from under the canopy like that is beautiful.

Yes, there’s two, here’s the other:


They’re old and hollow, and some branches have died, but they’re still huge trees. I saw where a couple shoots from the main trunk have gotten a little pruning, so I guess I was at the right place.

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Very! I forget when those railroad station gardens were planted, but I think it was in the 1930s or 1940s. The old photo of the tree from the 1950s is an already full sized tree. I don’t know if they both were planted originally, or if one is just a very old seedling of the other, though.

In other news, the own-root clone of Aravaipa is very very dead, at least above ground, after being unprotected for the recent freeze:

And after the recent warm nights, Brissago is starting to swell. Looks like only vegetative flush on the only terminal buds swelling so far, though:

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So I think my avocado didn’t survive 19 degrees but what is interesting is that it stays green around the buds.

That’s a shame. I forget, was it still in the pot or had you put it in the ground? Most of the hardier seedlings will come back from their roots at least after 19°F, but less often in containers, as the roots get colder then.

Just doing a State of the Buds post for every in-ground variety in the greenhouse. You can click here to see the full list of grafted varieties, which includes all the ones listed below.

Aravaipa (barely budding out, no sign of flowers yet):

Brissago (barely budding out, no sign of flowers yet):

Duke (flower buds just starting expanding):

Jade (flower buds expanding):

Joey (flower buds furthest along of any):

Linh (looks like very early signs of flower buds):

Long South Gate (essentially still dormant, no sign of flower buds):

Stewart (early stage flower buds):

Teague (essentially still dormant, no sign of flowers yet):

Walter Hole (extreme levels of flowers expanding):

Wilma (still dormant, no sign of flowers):

Bonus bud shot, the one below is #169, the rootstock for the grafted Jade tree that I got from Oliver Moore in Gainesville, FL. He said their rootstocks were all just a random assortment of seedlings from different varieties they have growing there, with the three most likely being Del Rio, May, or Wilma. It has the fuzziest, brightest pink new growth of any avocado tree I’ve ever seen, but it’s too early in the season to see the full color in the photo below. You can click on the profile link above to see it over the last few years, though.

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Just wanted to say thank you @swincher, and to keep up all the good work—I’m slowly catching up with the thread but have been following for over a year. As one who is also pretty ruthless about keeping plants unprotected (every death is more data—though I realize you have to be a little careful at this early stage) and avoiding sensationalist and imprecise gimmicks like pickle barrels and Christmas lights as much as possible, I’m glad you’re getting not only real data, but making real scientific progress—which gimmicks can’t ever do. Even with climate change, avocados aren’t likely to be a reality in my area within the century (heavy wet clay and rain), but these types of trials (which I also note, according to your website, have respect for the native cultures) are part of the path forward when it comes to securing the food supply, keeping people safe, and making sustainable orcharding viable.

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Thank you for the kind words!

I usually advise against starting avocados in water, as sometimes it encourages rot and often the roots become damaged or suffer when transitioning into soil. However, someone who knows of my avocado obsession gave me an “avocado vase” as a gift back during the holidays, so I am breaking my usual rules with this one (a seedling of Hamada from @george). It is fun to see the root structure, at least. I’ll be moving this to soil soon, though:

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