Very nice results!
Unfortunately temperatures during our winters can stay below freezing for an entire week. Unlike this event where we got cold temps and pretty quick bounce back. I wonder how they’d do when there is no warm up period.
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Last winter when it was 6 days below freezing with a low of 16°F, there was nearly 100% dieback to ground level on first-year seedlings, and only about 30% re-grew in the spring from the roots. But this year there’s a much wider array of different seedlings, including some healthy second-year trees. I’m hoping this winter won’t have another freeze like last year.
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Just got a WHOLE BUNCH of seeds from a generous collaborator in Gainesville, FL, including 45 Del Rio seeds (!!!), and smaller bags of some other varieties. Looks like the spring 2024 tree distribution will have lots of trees available!
Here are the Del Rio seeds going on the heating pad to germinate:
And a few of the others being rinsed:
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I’ve had pretty good luck just germinating them piled in a glass jar with a lid. I just open occasionally to rinse them off (which keeps the moisture level about right). As they germinate I pull them out and pot them individually. It’s a good way to minimize the space they take up prior to germination. I haven’t tried germinating them with supplemental heat though.
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I’ve tried a few methods, including something similar to that, and they all work pretty well. Be very diligent about fungal spots appearing if they are piled on each other, it’ll spread fast.
Heat and light both seem to help germination, but the most important thing is to keep them from drying out, but without being too soggy or getting anaerobic. I like soil takeout trays on heating pads because they are easy to inspect and don’t require much tending other than an occasional misting and removing sprouted seeds.
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How long does it approximately take to get to fruit bearing age? How large does a seedling avocado need to be before it can produce fruit?
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I had one seedling Hawaiian avocado take 7 yrs to fruit, the second seedling tree took 17 yrs to have the first fruit. Still have both trees, but the one that fruited earlier has better tasting fruits so I’m keeping that one, but the other larger one is used as my rootstock tree for multi-grafting other varieties.
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My understanding is Mexican varieties are often much earlier to fruit than Guatemalan types, though there is huge variation. Both of the people who have been helping with this project from Gainesville, FL said their Mexican avocado seedling trees typically first fruit between 3 and 8 years.
From the papers I’ve read, it seems total nodes is likely the trigger for flowering, but there’s lots of variation from seedling to seedling.
I’ll be grafting the hardiest seedlings we find in the project back onto mature greenhouse trees in the hope they will flower sooner there, and will also be cloning named cultivars via rooting, in case any of the named cultivars actually prove hardy enough to survive most winters.
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How large do they need to get before fruiting?
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As I understand it, that also varies a lot. I have only been growing seedlings for a couple years now without any flowering. I’ve heard that seedling trees start fruiting around 12-15’ in north Florida, but it may be different in our climate.
Grafts flower in one year and my understanding is usually start holding fruit within 3 years. Based on the size of my greenhouse trees, I’m expecting at least some fruit set this coming year, but maybe only a few. They flowered a lot last winter/spring, but no fruit.
Since I’m expecting to kill almost all the trees I’m growing outdoors, I’m not too worried yet about how long it’ll take them to flower. I’ll be excited enough if any of the outdoor trees get anywhere near flowering size!
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I just went around and looked at the trees again now that they’ve all had a few days to show more clearly the extent of their damage from two nights in a row around 25°F. This isn’t a comprehensive list of all the trees outside, just an overview of some notable winners & losers.
Minimal damage
The seedling showing the least frost damage of all is #138, a seedling of Aravaipa:
I am excited that I happened to plant that tree in such a prominent location in the middle of the front lawn. Hopefully we avoid any severe freezes this winter, as I’d love to see that tree get bigger before facing a harder test than this one.
The small graft of Aravaipa that’s outside shows no visible damage:
Same goes for Poncho/Pancho (upper branch in this photo), though its “Purple Nebula” seedling rootstock (lower branch) shows slight leaf damage:
Northrup/Northrop still shows only minimal damage, though the “Purple Nebula” seedling rootstock (lower center branches) shows more moderate/significant leaf damage:
Mild to Moderate Damage
This second-year seedling of Mexicola Grande made it through the first 25°F night without any sign of damage, but the second morning the leaves were covered in quite a bit of frost, and that frost appears to have caused leaf damage, though for some reason only on some of the branches:
This first-year Duke seedling shows the least damage of any of the Duke seedlings, with only the more tender leaves damaged and the buds and older leaves mostly fine:
The other first-year Duke seedlings mostly show only slightly more damage, but some of them seem to have stem damage near the growing tips and curling of more mature leaves:
This first-year Aravaipa seedling is a little more damaged than its hardier sibling at the top of this post, but still not too bad considering it was a less vigorous and smaller tree:
Here is the least-damaged Royal-Wright seedling, a second-year tree, and the only Royal-Wright seedling not in the serious damage/death category:
Here are a couple Mexicola seedlings, both first-year, and both with only moderate leaf damage and intact stems/buds:
Serious Damage / Death
This second-year Bacon seedling, which regrew from the roots after last winter, looks like it will have to try to do the same again this year, as it seems to have suffered complete leaf death and near-complete stem death:
The most vigorous tree from last year (a Royal-Wright seedling) looks like it might be in the process of dying back to ground level again:
Here are a couple other Royal-Wright seedlings (first-year and second-year, respectively), which show similar severe damage:
Observations
Based on this, I think I will be culling “Royal-Wright” from the grafted tree collection – only one of its seedlings seems to have survived somewhat unscathed, and even the larger second-year seedlings look to have taken severe damage at only 25°F. Since it is one of the larger branches on a greenhouse tree, it can make a framework for grafting something better, perhaps Northrop or Mexicola Grande, both of which are not currently grafted on in-ground greenhouse trees.
“Aravaipa” looks like a really good cold-hardy option, as it is both the least-damaged graft and has the least-damaged seedling. So far the “winner” varieties based on either grafts or seedlings’ hardiness are:
- Aravaipa
- Poncho/Pancho
- Northrup/Northrop
- Mexicola Grande
And the experiment continues…
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It was the best grape crop I have ever had. Damn raccoons got to the ones I left on the vine when I was away Canadian thanksgiving weekend.
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Interesting that you have had 25F already. Looks like those lows will be making their way to Victoria next week 
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After failing to get “Duke” on its own roots last year, I’m trying again using the latest version of my process. First, I remove just the most recent flush from a branch, right before it has fully hardened, and trim/divide that to keep only the few most recent leaves from each active growing tip:
Those all sit in the back of an aquarium filter (medium removed), with a heater in the water keeping it in the upper 70s:
Most of them stay alive and form callus, occasionally some wilt within days. Once they seem to be forming root-like bumps, they move to soil. With this method I’ve seen very few that die in the first few months compared to putting them straight in soil. I haven’t been doing it this way long enough to know if it will just have a higher failure rate later in the process, though.
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This seedling continues to impress. It’s in a very unprotected part of the yard and still shows the least frost damage of any seedling outside. We’ve had about 5 hard frosts (including three around 25°F/-4°C), and a dozen milder frosts all in the last month. Here’s a photo from yesterday:
The outside graft of Aravaipa has also been impressive:
I know I’ve seen some skepticism about the hardiness of Aravaipa because the main guy who introduced it gives off a scammy vibe, and made some questionable claims about it, but I think this is definitely a good source of hardiness genetics, even if the fruit quality is only mediocre.
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I posted a thread on mastodon with some photos (viewable without an account), but just realized I didn’t ever post an update here since the December freeze. Here’s the temperature chart for the freeze, which was only really bad for one night:
I was leaving for 2 weeks right before the freeze, so covered up more stuff than usual. Pretty much everything other than Poncho is showing some damage, but lots of them are still relatively alive looking.
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Interestingly, the least-damaged seedling (#138, Aravaipa seed parent) is apparently starting budswell already, here’s the main top/central leader:
That branch had wisely stalled at the very start of a fall flush, but it looks like the stalled buds are getting larger again now.
The three non-terminal buds on the only secondary branch weren’t even visible a week ago, so that’s more typical of how early bud swell looks for an avocado:
It’s been a little warmer than usual for us, but I’m surprised any avocado tree would be waking up with temperatures in this range over the last few weeks:
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@swincher, I read enjoyed your thread. It took a while but I finally got thru it. I can tell you are passionate about your lil avocado trees.
I noticed today on a walk that some plum trees are swelling like they want to open. I could see the margins of the actual blossom. They seem like they are 8 weeks too early. I just thought hmm hope my trees don’t open too early.
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First sprout of the season just dropped! This is a seedling of Aravaipa, and the boldest little fella out of ~80 seeds in the greenhouse this winter:
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It is funny how they have no mechanism to wait for spring to sprout. Probably since they’re adapted to warmer climates they are at an advantage if they can already be well established before summer hits.
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