Avocados and Frost in Europe (plus info on the cold-hardiest avocados and how to grow them)

Henry Jabel wrote: I would look out for more hardy varieties when you pass a greengrocer they tend not t have them in the supermarkets so much.

As well as the 'Hass' ...

'Fuerte' - I had two growing outdoors: https://imgur.com/a/0XuODou
Unfortunately, following the cold weather in early 2021, I mistakenly uprooted one of the plants thinking it had been completely destroyed by frost, only to find there was life still in the root system! So, I kept the remaining one. Even though recent DNA analysis has reclassified 'Fuerte' as being 'pure Mexican', I'll be surprised if it shows much less frost-sensitivity than the 'Hass'.  Even though it originates from around 2000 metres altitude (Valley of Atlixco), the temperatures there apparently never seem to fall below 0°C, so the genetic selection pressure for cold hardiness would appear to be absent ...

'Bacon' - found these at the supermarket, bought a few and planted six of them in our loft:  https://imgur.com/a/FmRvs7d
They'll go outdoors to their permanent position in a few months. Though grafted Bacon plants appear to resist temperatures to minus 5°C, I'm unsure how they'll behave growing on their own roots ...

Ooooh!  Congratulations on finding the Bacon!  Well jealous!  My seedlings are pootling along.  I have about three that have stayed in the slightly heated greenhouse all winter - I've managed to keep it above freezing thus far.  The others are all clustered on windowsills.  I've had a few deaths, including one that was abducted by a squirrel when but a few days old!  The Mexicola Grandes, having had a strong start, are not looking good now, I don't know if I should feed them.  The Gems are all looking amazingly strong.  Everything else is somewhere in the middle. The Israeli Galils are still very bijou and compact.  I've not snipped a few to see if it makes any difference to bushing out.  None of mine is actually looking any bushier for having been snipped.  One of the rootstock from Troipcaflore died, that was I think the seedling, the other, which I think is the Duke7, after a bit of a dodgy moment until I repotted it is now looking ok.  It too is in the greenhouse in an airpot.

I've not had chance to get over to the avocado tree near where I work, but I wave to it every time I pass it on the train.  It is looking glorious as ever.

I thought I'd updated this thread on Gerry's avocado trees in Texas - they're alive!!!  Well some of them are. He lost all his citrus trees, and some of his avocados, but all the Mexican ones survived.  They lost about 60% of their canopy but they're still there.  -22C for several days!  Incredible!  Hope for us all.

Alcina Pinata wrote: I've had a few deaths, including one that was abducted by a squirrel when but a few days old!

Squirrels seem to really like avocado roots. If planted outdoors, peg chickenwire onto the ground around the base of the tree to deter them. Otherwise they can do a lot of damage. With failed acorn yields this year around the country, squirrels appear to be digging holes everywhere in search of food ...
 

The Mexicola Grandes, having had a strong start, are not looking good now, I don't know if I should feed them.

Several possible causes here - difficult to say without more information. Are the pots deep enough (they don't like a restricted root system)? If roots are growing through holes at the base, transplant to a bigger (deeper) pot. If the seed is still attached, then they won't need fertilizer right now. I wouldn't fertilize anyway during the dormant winter period.  It may be a combination of winter light levels (short days & low intensity)  and warm temperatures, particularly at night, which is bad for most plants.  

I've not snipped a few to see if it makes any difference to bushing out.  None of mine is actually looking any bushier for having been snipped.

The best time to release apical dominance (pruning) is during late Spring & Summer, when growth is active - not something to do when growth is slowing or stopped, i.e. in the Autumn/Winter period.
 

Duke7 ... I repotted it is now looking ok.  It too is in the greenhouse in an airpot.

Is an "airpot" one of those pots made with holes around its sides, created to air-prune the roots? If it is, I can't see your plants adapting well to this. Avocado plants hate any root distrurbance.

With more details I could be a bit more specific, but hopefully you found something above that might be helpful.

PS. I saw the name "Pinata" & wondered if you were related to "Susanna Pinata" on Jack Wallington's weblink on avocados or maybe you're the same person ...  

Down to just Ettinger and Fuerte here now. Definitely have a disadvantage climatically compared to you two so hopefully the Ettinger espalier along a  south facing wall will work.

I am going to search all the avocados in Morrisons next time I go so fingers crossed for finding a Bacon!

Henry Jabel wrote:Down to just Ettinger and Fuerte here now. Definitely have a disadvantage climatically compared to you two so hopefully the Ettinger espalier along a  south facing wall will work.

How cold can it get where you are, and for how long?  I notice temperatures in Worcester (this week) are pretty much the same as ours here in St Leonards here in the southeast.

You can protect an avocado tree, up to about 2 metre height & spread, with fleece supported by a wigwam of bamboo-sticks & inverted plastic bottles. Two metres is about the size-limit, as it just becomes too onerous beyond that size. I found fleece only really keeps the temperatures warm during brief cold spells, e.g. predawn. If freezing temperatures hang around all day, or longer, the plant material is likely to succumb eventually.

Henry Jabel wrote: the Ettinger espalier along a  south facing wall ...

That sounds really interesting Henry, with the protection & extra warmth of the S-facing wall.  The horizontal branches would seem to lend themselves to training the tree in this way ...

Well its not too bad overall the absolute coldest its been since I moved here was -7C it didn't sustain it for too long and that seems the exception rather than the norm now. However that can make the difference between survival and not for these things and the sea and central London would buffer that drop so it doesn't affect you. .. I am going the espalier wall route for this reason and it might have a polycarbonate overhang too for good measure as I like to make things 'idiot proof' because I can forget to fleece things!

Henry Jabel wrote:Well its not too bad overall the absolute coldest its been since I moved here was -7C it didn't sustain it for too long and that seems the exception rather than the norm now.

 With the 'Beast from the East' we can get down to minus 6 to 7 degrees C too, e.g. winter 2018.  Do freezing temperatures, where you are, hang around for most of the day or are they generally limited to just before sunrise ?

However that can make the difference between survival and not for these things and the sea and central London would buffer that drop so it doesn't affect you.

 The microclimate on the St Leonard's seafront, is quite different to where we are - we're 1.8 Km inland, high up, but very exposed to coastal gales. It rarely freezes on the seafront, though our location can be a bit of a frost-pocket on an N-facing slope. The good thing is that being on a slope, the cold air tends to flow downwards, and not accumulate around the Hass tree or other plants. Also the tree is in a very sunny position, getting direct sun almost all day long, even in winter, which is important for any cold-hardening (in most plant species) - I assume that's the same for the avocado, though that's an assumption on my part.  

I am going the espalier wall route for this reason and it might have a polycarbonate overhang too for good measure as I like to make things 'idiot proof' because I can forget to fleece things!

  Sounds like a good plan, Henry - hopefully it will do the trick. Fingers crossed for the rest of the winter.

The coldest was -7C in the morning after my daughter was born so I remember it. After than it was still cold but less severe more around -5C and would have been 5 years ago now.

I had a a poncho and Mexicola grande from Chris but they succumbed to root sucking aphids after being outside under cover . Perhaps Joe tropicals youtube channel has a source?

I am trying to convince my gardening customer to get some seeds from London but don't hold your breath on that as I have not found a source in shoreditch just yet!

Henry Jabel wrote: I am trying to convince my gardening customer to get some seeds from London but don't hold your breath on that as I have not found a source in shoreditch just yet!

"some seeds from London": is there really a source of genuine Mexican seed in London ..?  [I raised my eyebrows in surprise when I read this]
(exclude Fuerte as it hasn't got much cold-tolerance)

Mike Guye wrote:

Henry Jabel wrote: I am trying to convince my gardening customer to get some seeds from London but don't hold your breath on that as I have not found a source in shoreditch just yet!

"some seeds from London": is there really a source of genuine Mexican seed in London ..?  [I raised my eyebrows in surprise when I read this]
(exclude Fuerte as it hasn't got much cold-tolerance)

I think it's in this thread furthur back there is a video from Joe's Tropicals on youtube eating an avocado from a London tree. The avocado is fully ripe and looks exceptionally good so the seed should be viable.

Don't have luck with Morrisons last time I went infact they did have any organic avocados. So hopefully that might change.

Henry Jabel wrote: I think it's in this thread further back there is a video from Joe's Tropicals on youtube eating an avocado from a London tree. The avocado is fully ripe and looks exceptionally good so the seed should be viable.

From what I've gathered, it's seems likely that the fruiting avocado tree in Southwark ("Joe's tree"), that you're referring to, is derived from a seed from a Hass avocado. Therefore, it originates from a Guatemalan x Mexican hybrid, and so its cold-hardiness limit is around minus 4°C or thereabouts.  I suspect it's not more cold-hardy than an avocado tree grown from any avocado you'd buy at the the supermarket here in the U.K.  As far as I remember, the Southwark tree failed the "crushed-leaf-test" and so therefore is not a pure Mexican (drymifolia) type.  As others have said elsewhere, it's likely that this tree owes its success more to the heat-island effect of inner London, rather than any enhanced cold-hardiness.

Ok I was getting confused which tree was which, but he does mention in the description of him knowing of five avocado trees in London. I saw a couple of small ones around the Kew area a few of years ago.

Even if most are surprisingly Hass related there must a Mexican one somewhere. I wonder where all central American community is in London would be good to find a greengrocer there.

Also 'lyonheart84 exotic fruit growing' seems to found a few, this has a great microclimate!

Henry Jabel wrote: Also 'lyonheart84 exotic fruit growing' seems to found a few, this has a great microclimate!
https://www.youtube.com/watch?v=Cvh0jPzZ6q8

Many thanks for that link Henry - I hadn't come across that one before. Yes, as you say, it's probably got the perfect microclimate, sheltered from wind, and surrounded by all that concrete & brick to store & radiate heat. Hopefully S-facing too.

The following link is the one for the Southwark fruiting avocado tree - that's often talked about - mentioned previously on this thread & posted by 'Joe's Tropicals' at:

It's this same tree that Joe got the avocado from to taste on his youtube video.

There are some really impressive close-up shots of this tree and its fruit at https://www.jackwallington.com/growing-avocados-in-london/

Mike, the guy who made that video said in the comments he heard there was that tree on facebook. So maybe perhaps that could be a potential source of Mexican seed? I cant check as I don't have an account! If so let me know!

'Exotic Food Plants UK'

https://www.facebook.com/groups/efp.uk/

Henry Jabel wrote:Mike, the guy who made that video said in the comments he heard there was that tree on facebook. So maybe perhaps that could be a potential source of Mexican seed? I cant check as I don't have an account! If so let me know! 'Exotic Food Plants UK'
https://www.facebook.com/groups/efp.uk/

I had a look at this link - no comments at all on avocados.
I think you made a comment earlier that maybe there was a shop somewhere in the U.K. selling Mexican avocados. I'm afraid this is unlikely.
The reason that pure Mexican avocado fruit  are not shipped outside of N. America, is because they have very thin skin (so thin in fact that you can even eat it along with the fruit flesh), which means they bruise very easily during transportation - not tough-skinned like the regular avocados that you'll find on sale in this country. You might find the Mexican ones on sale in local outdoor markets in areas where they are grown in North America. Therefore, it's unlikely you'll find fruiting pure Mexican avocado trees in the U.K. (at least at the present time).  Maybe in a few years, some of Chris' pure Mexican seedlings (that he talked about on his GoTropicalUK youtube channel), that he sold to folk here in the U.K., may eventually fruit, but until that time comes I think we're reliant on pure Mexican seed from either N.America and possibly Spain.  

Hello Henry and Mike,
maybe i can help. I know someone who used to regularly get mexicola seeds. I have one mexicola tree growing in my garden. It's a seedling from the seeds my friend sent me. Send me a private message if you want to try and inquire.

Update on my outdoor avocadoes.

Philip Heinemeyer wrote:Update on my outdoor avocadoes.

Ouch!  Are there any buds on it, that look like they haven't been killed?  Being in pot, I suspect there wasn't much temperature-buffering to the roots during the cold spell. What temperature caused this damage?  The seedling phase of growth seems to be quite frost-sensitive, unlike older plants developing bark.    

I have a small mexicola seedling that i totally neglected and despite having suffered some good freezes it is still alive. I didn't look after it because i kind of lost interest in mexicola as a variety. They are just not cold-hardy enough for where i live.
My mexicola growing outside froze back to the ground last winter but it grew back from the roots. It's quite amazing how much it grew last year but now it's really very damaged again. So i don't think it will ever fruit if it always dies back down every 2 to 3 years.
Compared to that the fantastic seedling, although much younger seems to show a higher cold tolerance.
And the one in the pot in my tunnel is now bigger than the one outside and is looking really good.
I will probably plant it out this year.

In summary the only realistic chance that i have is to try and continue with seeds of the most cold hardy varieties i can find.

Philip Heinemeyer wrote: ... And the one in the pot in my tunnel is now bigger than the one outside and is looking really good.

Philip, maybe best to keep them in your polytunnel in good-sized pots, and only plant them outdoors when they start developing bark on the trunk usually at the 2 or 3-year-old stage. The one grown in the tunnel looks really healthy, but I think it needs a bigger pot with some vermiculite added to the compost/soil mix to lighten it - avocados seem to hate having their roots restricted. I think the one that got clobbered by frost, but still has some green leaves, has a chance of recovery.

Philip Heinemeyer wrote:Update on my outdoor avocadoes.

Yeah they are vunerable when young. Mine looked rather similar when stored under an overhang during a cold snap they started to recover then died off later despite my best efforts. I found later the stress must have attracted some root sucking aphids that finished them off.

Philip Heinemeyer wrote:
My mexicola growing outside froze back to the ground last winter but it grew back from the roots. It's quite amazing how much it grew last year but now it's really very damaged again. So i don't think it will ever fruit if it always dies back down every 2 to 3 years.

Just a thought Philip, for your Mexicola that always dies back down every two to three years, which you showed in one of the photographs you posted above (scroll back 4 posts) ...

If the freezing cold weather is mainly at night, and not during the day, you could cover it with a large plastic container, e.g.  a 100 Litre plastic rubbish bin (ours is 60 cm high), or a large water butt (we have one shaped a bit like a giant flower pot, wider at the bottom when inverted, and 80 cm high).  With the larger young trees, on the nights a frost is expected, I drape a fleece cover on the plant, then invert the plastic bin or water butt over this (to keep the fleece dry & protect from cold winds), then weigh down the plastic bin with some bricks on top. This seems to work with my young trees growing outdoors but, when their height exceeds 80cm, I'll have to think of something else - hopefully by then most will have started to develop bark, and therefore be more freezing tolerant, at least to  −3°C. Obviously, following sunrise, you'll need to remove the plastic bin and fleece, otherwise it'll die if kept in darkness.  This method works when freezing temperatures are limited to the hours of darkness, but not if a cold front persists for several days.

The links below show my personal experiences with avocado growing - they are ongoing, getting updated when I take new photos:

Hass:  https://imgur.com/a/5gflnlU

Hass (winter protection):  https://imgur.com/a/q3j3zCn

Fuerte:  https://imgur.com/a/0XuODou

Bacon:  https://imgur.com/a/FmRvs7d

Mexicola:  https://imgur.com/a/2wJArWr

Has anyone seen these avocado fruit on sale in the U.K:  

‘Brogdon’ or 'Brogden'?
‘Ettinger’?
‘Gainesville’?

Thanks in advance for any possible leads on these ...

Both of my avocadoes growing outdoors died back to the ground but are sprouting back from the roots. It wasn't even that cold last winter.
I didn't protect them.
One of them is a mexicola seedling that must be at least 4 years old now.

The other one is a fantastic seedling that i planted out last year. It also is growing back from the roots, while my third one that is also a fantastic seedling that i planted into my polytunnel is growing ok and didn't die back.

This makes me think that checking for cold tolerance and finding that some mexican avocadoes can survive minus 10 Celsius does not mean at all that your tree won't die when it's minus 3 next winter. There is many other factors that are important. I thought before that trees must be somewhat older and already have bark before they can resist frost.
There may be some truth to that but i think humidity and heat units in summer are also really important.

Imagine yourself wearing dry clothes in an open field in texas by minus 10 degrees Celsius in winter.
You would be less cold than wearing soaking wet clothes in an open, windy field in Oregon by minus 2 degrees Celsius.

The temperature alone does not count. Why else would my seedling in the polytunnel survive the winter no problem?
The polytunnel does not have a higher temperature at night in winter, but it's drier and the moisture doesn't come down and cristallize on the leaves as happens outdoors.
I have not yet tried to plant seed grown 3 to 4 year old bigger plants outdoors, but for now it's not working.
Avocadoes, up to now, won't grow outdoors in a northern european climate.

Try and get mexican avocado seeds and grow plants in polytunnels, pruning them back regularly. When they give fruit you'll have plenty of seeds to try growing outdoors.

Philip Heinemeyer wrote:Both of my avocadoes growing outdoors died back to the ground but are sprouting back from the roots. It wasn't even that cold last winter.
I didn't protect them. One of them is a mexicola seedling that must be at least 4 years old now.

Even the Mexican avocados need winter protection outdoors, for the first 2-3 years from winter weather. Philip, start protecting them from winter 2022/23 with fleece, an inverted bin, anything you can find, etc. Green stems are more frost-sensitive than the older wood.  

The other one is a fantastic seedling that i planted out last year. It also is growing back from the roots

The soil will be thermally buffered, compared to the air, hence the base of the stem is protected at least to some extent, which is why regrowth can occur.

...while my third one that is also a fantastic seedling that i planted into my polytunnel is growing ok and didn't die back.
This makes me think that checking for cold tolerance and finding that some mexican avocadoes can survive minus 10 Celsius does not mean at all that your tree won't die when it's minus 3 next winter. There is many other factors that are important. I thought before that trees must be somewhat older and already have bark before they can resist frost.

As you say winter damage is not merely about temperature itself. It's a combination of different factors, often linked by low temperatures. For example, dessicating winds at a time of reduced water uptake by the roots (made worse when the ground is frozen), and poor drainage of cold soils, predisposing roots to disease, e.g. root-rot by Phytophthora. With drops in temperature, the rate of cooling is important too: a rapid cooling-rate is likely to be significantly more damaging  than a slower decline. Maybe your polytunnel  slows down cooling-rate, particularly when there is a radiation frost ...

Mike Guye wrote:Has anyone seen these avocado fruit on sale in the U.K:  

‘Brogdon’ or 'Brogden'?
‘Ettinger’?
‘Gainesville’?

Thanks in advance for any possible leads on these ...

I have had Ettinger a few times. Seems to be one of the more common ones after Hass along with Fuerte for me. If I recall correctly it was grown in Spain (I remember looking it up finding out the cultivar is from Israel and surprised it wasn't from their like a lot of Hass are)  so I think you have a good chance of finding it providing they haven't given up due to the drought this year.

Mike Guye wrote:Has anyone seen these avocado fruit on sale in the U.K:  

‘Brogdon’ or 'Brogden'?
‘Ettinger’?
‘Gainesville’?

Thanks in advance for any possible leads on these ...

Ettinger definitely. I have several Ettinger seedlings.  They are like Fuerte but don't peel well.  Tasty though.  The others I have never seen for sale in the UK.  Unlike Haas which is available all year round, Fuerte, Ettinger, Pinkerton, etc. are usually available here seasonally, over the winter months.

Philip Heinemeyer wrote:
The temperature alone does not count. Why else would my seedling in the polytunnel survive the winter no problem?
The polytunnel does not have a higher temperature at night in winter, but it's drier and the moisture doesn't come down and cristallize on the leaves as happens outdoors.

I can't remember where I read it, but the polytunnel "roof" will be making a difference.  In places where they grow avocados but it sometimes goes a bit too cold for comfort in the winter (e.g. Northern California) if they can they wrap up their avocados in the winter. If they can't wrap them up then, and this is the exact bit I can't remember where I read it, even something like a golf umbrella over the top can make the difference between die back and death.  So exact same temperature but the roof is still protecting the plant from frost. It's the frost that does the damage.

Jerry Satterlee's Mexican avocados in Texas survived several days very subzero temperatures at -22C. There was 30-40% die back, but they survived.  If they can survive that then they can survive in many parts of northern Europe.  Jerry has always maintained: do not plant outside until they have brown bark, or at the very least wrap 'em up and protect them from frost until they do. Jerry buys grafted trees and with those further maintains: buy ones with low grafts and bury the graft (again when they have brown bark). Whilst the top growth may be Mexican, the root stock undoubtedly isn't.  And yet...his grafted trees survived -22C for several days.  Rootstock and all.  So he's doing something right. His citrus all died including the more cold hardy mandarin- so if you can keep citrus alive over winter then you can keep avocado alive.

I think what we probably can't do in Europe, like they can in Southern California, is just toss a seed in the ground and wait a few years and behold we have an avocado tree.  I think we will have to coddle and nurture carefully for the first five maybe even ten years. And yes we will still have more deaths than they do in Southern California.  The fact that your polytunnel avocodo is thriving is excellent.  Personally I'd keep it (and any new ones you try) in the polytunnel until it has brown bark, and only then try planting one or two outside.

My rootstock avocado (the grafted trees I purchased arrived broken below the grafts) is going to be now probably 4 years old and it still doesn't have brown bark. So our coddling, nursery phase may be quite lengthy. But I'm hoping we shall reap great rewards for our care in the end.

Whilst we're doing show and tell...

These are the seedlings and the rootstock plant in the the greenhouse which is on the north side of the house, so plenty of light but no direct sun.  In the winter this has a couple of little heaters that has managed to keep it above freezing on sub-zero nights. Lowest night in the middle of the garden was -5C, but the greenhouse went to 0C.  The rootstock (might be Duke7 or an unknown seedling, probably Zutano therefore as I believe most commercial rootstock seedlings are Zutano) has variegation in some of its leaves.  This, from what I have read, may actually be a virus and not the "distinctive yellow flecks of a Duke". Sigh....  It is in an airpot. The reason for this is that I understand that avocado roots like plenty of air. Gary Gragg's YouTube channel shows some of his avocados that he had on a temporary display put their roots out through the small pot they were in, and had lots of healthy white roots just pushing their way into the dry bark chip that was filling the gap between their small pot and the large display pot. I thought an airpot may provide the same type of environment i.e. plenty of air.  Certainly since putting it into the airpot it has fared much better!  The others avocados seedlings are Gem and Brazos Belle (assuming I trust the seed seller). This summer the middle of the garden reached 43C and the greenhouse was 38C for several days. All seem to be doing very well.  The Gems are noticeably paler, even though I have fed them.



This is the avocado forest in my south facing window.  A large mixture of many different types (fuerte, gem, ettinger, pinkerton, mexicola grande, brazos belle, poncho, galil, fantastic). All sown winter 2020-2021. They get a lot of sun through the window in winter, less direct sun in summer but they can get quite hot!  When the temperature is set to go over 26C the curtains get closed to try to keep the house cooler, and so they are trapped between the glass and the curtains.  The glass is double glazed so even the leaves touching the glass are undoubtedly not going to suffer cold damage in winter.



This is the avocado forest in my west facing window. Again a large mixture of different types all sown winter 2020-2021 with the exception of the larger fuerte which was sown the year before. This window gets very hot in the summer - in fact during the heat wave the UK had a couple of weeks ago, I hung shade cloth outside the window in an attempt to prevent so much heat coming in.



What is noticeable, regardless of where they are being grown, the Gems are the most vigorous and require a lot more watering. I water only with rain water. The Mexicola Grandes seeds decomposed away the quickest and needed feeding before any of the others.  The rootstock also benefited greatly from feeding.  Feeding makes a big difference, who'd have thought! :)  But I have been wary of overfeeding as the conventional wisdom is that avocados really struggle with salt buildup.  I have lost 5 or 6 of the seedlings, don't know why, they just died!  Another 2 or 3 are alive but have always appeared on the sickly side - this includes my original Fuerte - very prone to leaf scorch and drop their leaves at the slightest stress.  2 germinated and grew into mutated plants - a Haas with a very small seed and a Fantastic. I believe this occurs when the fruit was harvested before the seed was fully mature.  Interestingly although their seeds are still intact I did include them in the feeding rotation this summer and both, in the last month, have put out new and non-mutated growth.  So quite fascinating!  The other plants are all pootling along nicely. All bar about 3 were snipped to encourage branching, doesn't seem to have had that much effect.  All pots have bark chips and dead avocado leaves covering the soil. All pots are only watered when the probe says the soil is dry.  The 'soil' is a mixture of potting compost, sand and perlite - so airy and very well draining, but not the most fertile.

Mike Guye wrote:The links below show my personal experiences with avocado growing - they are ongoing, getting updated when I take new photos:

Hass:  https://imgur.com/a/5gflnlU

Hass (winter protection):  https://imgur.com/a/q3j3zCn

Fuerte:  https://imgur.com/a/0XuODou

Bacon:  https://imgur.com/a/FmRvs7d

Mexicola:  https://imgur.com/a/2wJArWr

Mike, your in ground avocados look amazingly healthy! Interesting that your Mexicola seeds rotted quickly, mine did too, but for the moment both of my plants are still alive, though one is teeny tiny (it produced 4 shoots from the seed but only the 4th and smallest survived).  I am well jealous you found Bacon avocados!  I look forward to the updates in your diaries.  Many thanks for sharing.  This collective experience of avocados in Europe is great!

Henry Jabel wrote:
I have had Ettinger a few times.

Henry, can you remember which supermarket chain you bought them from?

Alcina Pinata wrote:Ettinger definitely

Alcina, can you remember which supermarket chain you bought them from. and roughly the time of year?

Alcina Pinata wrote:
Mike, your in ground avocados look amazingly healthy!

Thanks Alcina, I'm always happy to share.
It's really no secret to get healthy avocado plants in the long term: paying attention to the root environment is pretty important, amongst other things. In summary, here are some key pointers that might be useful to pass on...

grow them permanently outdoors in the ground, to provide unrestricted root growth

find the sunniest spot in your garden, direct sunlight rather than shade - indoor plants don't get enough good quality light

the need for unrestricted root growth is the reason pot-grown avocados often seem to have issues, e.g. browning of  leaves, lack of vigour, etc

roots need good drainage, particularly in winter, a sloping site is ideal - plants won't thrive on cold soils that remain wet for long periods

roots mustn't be allowed to dry out in hot weather - water generously - maintain near-constant soil moisture levels by ongoing mulching

roots are very sensitive to disturbance so, following transplanting, plants may sulk for weeks, before resuming shoot growth (***see below)

after transplanting, protect the plant from potentially excessive water loss during this period, otherwise the tree may die due to water stress

winter protection, i.e. shelter from strong winds & freezing temperatures - particularly important before bark develops on the main stem

 
***if transplanting from a pot to the ground outdoors, my experience is that the transition is usually very smooth as there is little (if any) transplant-shock, growth continuing uninterrupted. The protection I recommended above relates to where transplanting is from one part of the garden to the other, the plant together with as big a rootball as possible, being dug out of the ground and planted in the ground elsewhere. This form of transplanting usually incurrs at least some root injury, that the plant needs some help to recover from.

Alcina, your location (inner London) is climatically very favourable for growing avocados. It's more advantageous than mine here on the SE coast, as you're sheltered from year-round gales, have hotter summers, and the heat-island effect gives you almost frost-free winters, or at most only light frosts when they occur ...

Alcina Pinata wrote: ... I am well jealous you found Bacon avocados!

I have a spare Bacon.
Would you be interested to swap it for an Ettinger? If interested I'll mail it to you.

Alcina Pinata wrote:This, from what I have read, may actually be a virus and not the "distinctive yellow flecks of a Duke". Sigh....  It is in an airpot. The reason for this is that I understand that avocado roots like plenty of air

The yellow flecks are likely due to root injury, arising when the ends of the roots dessicate on arriving at the air holes in the side of the airpot. It's my opinion that an airpot is unsuitable for avocados, given how sensitive their roots are to disturbance/injury.  If you want a light and well-aerated substrate, mix compost with vermiculite in a volume ratio 2 parts  compost : 1 part vermiculite - a coarse-grain vermiculite is fine.

Alcina Pinata wrote:... Whilst the top growth may be Mexican, the root stock undoubtedly isn't.  And yet...his [Jerry Saterlee's] grafted trees survived -22C for several days.  Rootstock and all.  So he's doing something right

 
This begs the question:  what rootstocks are Jerry Saterlee's plants grafted on, that survived −22°C ?  
As the Mexican rootstocks are the most frost-hardy,  wouldn't it  seem more logical to grow Mexicans on their own roots, or at least graft them onto other Mexican rootstocks, in regions where freezing temperatures are the main consideration?
 
However, I have understood that there are other considerations, apart from freezing resistance for plant survival, as Philip has already hinted at in one of his posts, when choosing a suitable rootstock adapted to local growing conditions. These considerations also include resistance to salinity (high soil salinity caused by intensive irrigation systems in warm-temperate climates where evaporation rates from the soil surface are high, and salt-laden winds in coastal growing regions), root rot (caused by the pathogens Phytophthora cinnamomi or P. citricola), as well as resistance to winter chlorosis (yellowing of the leaves). Both root rot and chlorosis are a potential problem on cool wet (not-frozen) soils.

I tried rooting avocado cuttings and it didn't work. Now i am trying to layer my avocado. Since i already did this before with other plants i am quite optimistic that this will work.
I need to keep the soil moist for about a year and since the plant is in my polytunnel that's harder than if it was outside.
The soil mix is one third washed sand, one third perlites and one third peat moss.
It retains moisture quite well and you can't really overwater it cause it drains really well.
The avocado seedling is a fantastic seedling that has a strong anis leaf smell.
I didn't have rooting powder this time.
Wedging a piece of matchstick into the cut is important as you want the wound to stay open.