most cold hardy avocado

[Unicyclemike]

Of these three which one do you think is the most cold hardy...Lila, Joey or Fantastic avacados?

Thank you.
Mike Adams

[drymifolia]

I would also love to hear of anyone who's really pushed the limits enough with those side by side to compare their damage/kill temperature at various sizes of tree. I don't think anyone should trust any nursery claims, though.

I had Joey grafted on a Hass seedling (graft buried 4") over the winter of 2021/2022, when we had a 6-day freeze (highs in mid 20s to low 30s, lows in low 20s with one night at 16°F briefly). The one year old graft defoliated but the stems showed only minimal damage and the dormant buds looked alive. 3 months later, the graft suddenly died as it began budding out, and when I dug down it looked like the rootstock had been dead for months, probably killed in that freeze and the graft took a few months to realize it had lost its roots.

My Fantastic graft runted out this year, so I'll be ordering another bundle of scionwood from Fruitwood this winter and trying a few more next year. So I've got no idea of hardiness for that one.

I grafted and rooted "Opal" this year, which some people have said is the same cultivar as "Lila," but I have no idea if that's been confirmed. The graft is on an outdoor tree, so I'll have an idea of its hardiness soon enough.

As for other cultivars, a first-year graft of Poncho made it through 17°F this last winter with zero leaf/stem/bud damage, protected only with an upside down flower pot on the coldest few nights.

Northrup made it through alive above the graft with no real protection at all, just a lawn chair on the north side. Significant stem damage and complete defoliation, but re-grew well this year.

Aravaipa was grafted high on a Zutano seedling, and even though Aravaipa showed no leaf or other damage from 17°F with just a plastic bucket over it, the rootstock was completely killed and the graft failed to grow in spring, suddenly wilting when I'd expect budding out.

This winter I have Aravaipa outside on its own roots to test it better, as well as grafts of Ganter and Magdalena. Along with the dozens of seedlings in the breeding project, that is.

[Unicyclemike]

Wow you know your avocado trees.  What zone are you in?  What if any protection do you provide?  Are there any cold hardy dwarf avocado trees.  Thank you for your help.

Mike Adams

[drymifolia]

What zone are you in? 

I'm in Seattle, which is an unusual type of zone 8b (and we really have moved to 9a in the last couple decades). It sometimes gets to borderline 8a temperatures during extended cold snaps, but other than that the winter is mostly rainy with lows in mid-upper 30s and highs in the mid-upper 40s or low 50s most days. Then in summer it's pure sun for 2-3 months with lows in upper 50s and highs in 70s-80s. Avocados love our summers! Here's a temperature chart showing my last two years:

What if any protection do you provide? 

It has varied from zero protection to upside-down flower pots and buckets, and even tried a cloth frost cover for one tree. I also have a greenhouse with multi-graft trees mostly in their second to third year. But the purpose of the project I'm organizing is to select seedlings able to survive and grow and even fruit in our climate, so once they've made it through one winter with protection, I generally won't protect them anymore. But I've also been distributing trees to members of the project, and they have discretion to choose how much they want to protect the trees.

Are there any cold hardy dwarf avocado trees.  Thank you for your help.

There are no dwarf avocado trees, period. Some trees grow more slowly than others, making them easier to control their size with pruning, but if you don't control them with pruning, all avocados will eventually become large trees. There are also no dwarfing rootstocks. UC researchers spent many decades trying to select dwarfing rootstocks and concluded it's not a trait that avocados have.

But the good news is most seem to respond pretty well to even very aggressive pruning for size, becoming bushy.

[digigarden]

here's an idea i can give you guys.

there's a genus in the avocado family: Beilschmiedia. there's like 200+ species and some are edible.

some of them are temperate to subtropical (they get really big though)


https://tropical.theferns.info/viewtropical.php?id=Beilschmiedia+anay

https://en.wikipedia.org/wiki/Beilschmiedia_berteroana

[agroventuresperu]

What zone are you in? 

I'm in Seattle, which is an unusual type of zone 8b (and we really have moved to 9a in the last couple decades). It sometimes gets to borderline 8a temperatures during extended cold snaps, but other than that the winter is mostly rainy with lows in mid-upper 30s and highs in the mid-upper 40s or low 50s most days. Then in summer it's pure sun for 2-3 months with lows in upper 50s and highs in 70s-80s. Avocados love our summers! Here's a temperature chart showing my last two years:

What if any protection do you provide? 

It has varied from zero protection to upside-down flower pots and buckets, and even tried a cloth frost cover for one tree. I also have a greenhouse with multi-graft trees mostly in their second to third year. But the purpose of the project I'm organizing is to select seedlings able to survive and grow and even fruit in our climate, so once they've made it through one winter with protection, I generally won't protect them anymore. But I've also been distributing trees to members of the project, and they have discretion to choose how much they want to protect the trees.

Are there any cold hardy dwarf avocado trees.  Thank you for your help.

There are no dwarf avocado trees, period. Some trees grow more slowly than others, making them easier to control their size with pruning, but if you don't control them with pruning, all avocados will eventually become large trees. There are also no dwarfing rootstocks. UC researchers spent many decades trying to select dwarfing rootstocks and concluded it's not a trait that avocados have.

But the good news is most seem to respond pretty well to even very aggressive pruning for size, becoming bushy.

My hat's off to you. As important as avocados are you think this project would be conducted or funded by some sort of institution.

[drymifolia]

My hat's off to you. As important as avocados are you think this project would be conducted or funded by some sort of institution.

Mexican avocados are pretty much considered unmarketable by industry groups, both because they are small and because the skin is so easily damaged. But for community gardens and food forests, backyard growers, etc., it would be great to be able to grow avocados in this area. I'm still not convinced we'll succeed, but I hope we can. The first two winters of the project were much colder than normal and some tiny trees managed to not completely die, so I'll be excited to see what we can do with a hopefully mild El Niño winter to allow some trees to size up a bit more.

[sc4001992]

drymifolia, did you try germinating the Aravaipa seeds, it might be the best method than to root a cutting.

[drymifolia]

drymifolia, did you try germinating the Aravaipa seeds, it might be the best method than to root a cutting.

I have also grown many Aravaipa seeds, but those will all be different varieties whenever they eventually flower in many years, so I'm also wanting to test the named cultivar itself.

Here's one of the clones of Aravaipa that I rooted last year:

[BeachGardener9a]

I am in north Florida zone 8b/9a. I have a large poncho in ground - the trunk is about 3 inches wide. Hoping that it is grafted on to a cold hardy rootstock but highly doubt it is. I have the graft buried (only by about an inch). I plan on adding more compost / mulch at the base to give the graft union a couple inches of protection under ground. we'll see.

I also have a fantastic the same size that I am keeping in 30 gallon pot until after this season.

[sc4001992]

drymifolia, that is a lot of growth you got from a 1yr old cutting. Did you grow the cutting in a greenhouse?

I was suggesting you use the Aravaipa seedling as a strong rootstock, not to get it to fruit.

[drymifolia]

drymifolia, that is a lot of growth you got from a 1yr old cutting. Did you grow the cutting in a greenhouse?

I started that one on a heating pad during winter of 2021/2022, it rooted by spring 2022, but hardly grew last year in its pot. I kept it in the greenhouse this last winter and planted it in the ground in early summer this year.

Here's when it first rooted, spring 2022:


Here's what it looked like early this spring (one year later):


And this is what it looked like when it went in the ground in early summer this year:


You can see all the photos I've taken of that particular clone here (it takes a few moments for all the images to load because my website code stupidly resizes them on the fly):

https://www.drymifolia.org/photos/?view=218

[drymifolia]

I was suggesting you use the Aravaipa seedling as a strong rootstock, not to get it to fruit.

Ah, I've also done that some, but no matter how hardy rootstocks are, I expect most of the trees I'm planting will eventually get killed to ground level or even a few inches below grade in a bad freeze, so having things on their own roots ensures I don't lose them when that happens.

[sc4001992]

Oh, got it, makes sense. You have some good, detailed photos of your work.

[BeachGardener9a]

I was suggesting you use the Aravaipa seedling as a strong rootstock, not to get it to fruit.

Ah, I've also done that some, but no matter how hardy rootstocks are, I expect most of the trees I'm planting will eventually get killed to ground level or even a few inches below grade in a bad freeze, so having things on their own roots ensures I don't lose them when that happens.

Can you share what technique you use for rooting a cutting? I have some rooting hormone (0.30 percent Indole-3-Butyric Acid) but have not successfully cloned any of my trees. 

[drymifolia]

I was suggesting you use the Aravaipa seedling as a strong rootstock, not to get it to fruit.

Ah, I've also done that some, but no matter how hardy rootstocks are, I expect most of the trees I'm planting will eventually get killed to ground level or even a few inches below grade in a bad freeze, so having things on their own roots ensures I don't lose them when that happens.

Can you share what technique you use for rooting a cutting? I have some rooting hormone (0.30 percent Indole-3-Butyric Acid) but have not successfully cloned any of my trees.

Success rates are not great even for Mexican cultivars (and virtually zero for Guatemalan and WI cultivars), and it typically takes 6 months or longer either in a mist chamber (ideal) or under a humidity dome (what I do) before it roots at all, and then another 12+ months after that before you will see vigorous growth. This long timeline and low success rates are the reason it is not done commercially this way. I discussed my method here, which seems to work equally well with and without rooting hormone:
https://tropicalfruitforum.com/index.php?topic=52398.msg503128#msg503128

I have also posted more detail and examples on another forum, here:
https://growingfruit.org/t/rooting-avocado-cuttings/34254

The commercial method used to produce clonal rootstocks involves etiolation and grafting on a nurse root, which is removed once roots form above the graft. I posted a study here that details that method, which has not succeeded in my primitive attempts, but clearly works best once you have the right setup:
https://tropicalfruitforum.com/index.php?topic=52398.msg502976#msg502976