Anyone here really pushing the zones hard? (maybe even successfully?!)

[naikii]

If you're zone pushing and not gonna bring your plants indoors, consider starting many marginal plants from seed. And preferably from varieties that are confirmed or suspected to be most cold hardy. For example, if I were in zone 8a I would try and source as many seeds from avocado varieties Lila, Pancho, Joey, Fantastic and Wilma as possible, and making sure those seeds were not pollinated by any variety less hardy than those. The seedlings may end up being slightly more or less hardy than compared to the parent/s since they will have degrees of genetic variation, but this can come to your advantage. Not to mention, I have noticed seedlings often are simply more tolerant of the cold than their clonal parents. This might have to do with a stronger taproot, I can't say for sure just an observation. For example, this past winter it got to 24F and all 5 of my air layered lychee saplings (brewster sweetheart and mauritius) had major branch splitting, however out of the hundreds of seedling lychees I have lying around unprotected (from those very same varieties), most of them only had very small twig, leaf, and new growth damage. But there are many factors involved.. The seedlings may have simply been out of the wind and much closer to the ground, which near the surface of the ground a bit of contained Earth heat always trickles out, so maybe that heat was just enough to prevent major splitting on those seedlings.. I couldn't say definitively.
But even a little dinky greenhouse or cover will help out greatly. The same winter event stumped all of my in-ground annonas, but I had a couple pots with freshly germinated seedling atemoyas in a TINY greenhouse under some bamboo, and none of them were even phased.
And on the topic of stumping, you will want to prune your marginal plants HARD. The larger the caliper of trunk and branches the MUCH greater chance they have of pulling through a bad winter event. You want the least amount of fresher smooth wood and the most amount of thick bark as possible on all limbs. For example, the same past winter event (24F) re-stumped a few of my in-ground mangos. The mangos had already been stumped twice over 5 years by other bad freeze events, so they have pretty thick caliper stumps. All of their smaller caliper branches that had no real wood were burnt down. However, the few inches of stump that are clearly woody pulled through just fine, and are sprouting new growth (which I will be pruning hard to hopefully get woody too). Same concept as with some of my in-ground annonas..
Also I'd recommend putting those prunings to use by trying to root them up, grafting, or whatever. Might as well..
Some people claim grafting a less hardy variety onto a cold hardy rootstock will increase hardiness of the lesser by a few degrees..
You mentioned jaboticabas. My sabaras were fine at 24F, not even leaf drop on any. I assume they could perhaps be okay even a few degrees lower. No idea how the other jabo varieties would respond to that degree of cold.
There are obscure varieties of annonas from nothern argentina/south brazil and uruguay that will withstand -6C. a.sylvatica, a. emarginata, a. ubatubensis come to mind. There are others too.
There are many fairly cold hardy citrus and avocados if you were interested. Wampee, kei apple, white sapote may be candidates too. feijoa, loquat are bullet proof. surinam cherry also takes the cold, though a couple of mine defoliated around 24F, but no branch damage. Someone on this forum told me his Luc's garcinia and some other garcinias actually withstood below 20F with not much damage. 12-15F was his low. It would be resourceful to not have a bunch of cold hardy plants unnecessarily taking up space in a greenhouse.
You could experiment by rooting cuttings and seeing at exactly what temperature or conditions they defoliate/die/become stumped before subjecting a bigger or prized specimen to those conditions, if you know what I mean. The results may surprise you.. but then again could be misleading because larger woodier plants are often more cold hardy than something like a small experimental cutting anyway..
Also you can try and mound your plants with a bunch of leaves.
And one last thing. I accumulate giant mounds of coffee grounds and have noticed they get VERY hot even in winter. Even small mounds. (significantly hotter quicker than a typical leaf & wood chip pile) Like 150F+.. It would be resourceful to utilize this heat energy, under a tarp and frame or something. You could have a big mound with a sealed tarp over it and pile all your potted plants around the mound still under the tarp. Or have a tarp set up and drag big totes of composting grounds under the tarp with the plants if you don't want the mound of grounds sitting directly on the ground. Just go around town and ask the coffee shops to save their used grounds and start accumulating.

Thank you for typing all that out, really helpful.

I have decided to add some extra layers of protection with frost cloth and 1200 old-school incandescent xmas lights. I hope that will add enough warmth on the codler nights.

I have been reviewing our past few years average temperatures as well. Typically in the coldest months we sit between around negative 1 celsius and +3 celcsius most nights. There is around 3-6 average nights per month going down to -4, and on average 1 or 2 days with lows at -6 or -7 per winter.

I have a very large assortment of plants right now, and I definitely dont want to lose them if it can be avoided, but am prepared for some to go and I can re-use the pots for more tolerant varieties in future.

On the way I also have a bunch of digital wireless thermometers so I can see the temperature protection the pergola is providing.

As a reference I had a potted hass avocado under there last winter and it got through with barely any signs of cold stress.

[Ulfr]

Yeah you really need a heat source or thicker coverings than frost cloth down there. I did some tests with data loggers and frost cloth and found while it was enough up here, it only kept them slightly warmer.

https://m.youtube.com/watch?v=x5Pf_n86cZI&t=3s

[K-Rimes]

1200 old school lights will do a LOT if you can keep them enclosed. That's 12,000W+ of heating at 10w each. It will not be cheap.

Your weather sounds like Vancouver BC where I grew up. While it doesn't seem that cold, it's the constant and frequent cold that never seems to warm that is tough on plants. Your number one issue to worry about is over watering. That has killed more than anything else here in the winter.

[naikii]

Yeah you really need a heat source or thicker coverings than frost cloth down there. I did some tests with data loggers and frost cloth and found while it was enough up here, it only kept them slightly warmer.

https://m.youtube.com/watch?v=x5Pf_n86cZI&t=3s

Firstly, great video, and good to see another Aussie on here. I love data driven information that shows empirically how much of a difference cold measueres make in the wild.

Secondly I thought that the difference provided by your (much thicker) frost cloth was quite sigificant. I bet in colder temperatures this difference would be even more pronounced.

Unlike your trees mine are on concrete pavers, with some right up against the brick wall of the house. These should act as a heat sink much like the water container with your jackfruit. The pots themselves are mainly black and should also absorb some heat during the day and hopefully radiate through the night. 

Although the frost cloth is quite thin, I have purchase 4 strands of 300 xmas bulbs which I will wrap around the pots and stems, and should radiate even more heat upwards overnight.

Here is an idea of what I have undercover https://www.youtube.com/watch?v=zVRIRDRf8FU, not quite as well put together as your own, but we do what we can!

[naikii]

1200 old school lights will do a LOT if you can keep them enclosed. That's 12,000W+ of heating at 10w each. It will not be cheap.

Your weather sounds like Vancouver BC where I grew up. While it doesn't seem that cold, it's the constant and frequent cold that never seems to warm that is tough on plants. Your number one issue to worry about is over watering. That has killed more than anything else here in the winter.

Constant frequent cold is right. I think you are spot on with the overwatering too, it is by far my biggest risk and I am really bad watering when they are still damp.

[CarolinaZone]

Yep, I'm in Zone 7a/b and I am doing in ground citrus. I am doing mangos and guava in an unheated greenhouse.

in an unheated greenhouse?? What are your general lows in winter outside and inside of the gh. What is the lowest temp that u have experienced in the gh , thank u :-)

To be honest, I didn't collect that data this year. Sorry.

[Ulfr]

Yeah you really need a heat source or thicker coverings than frost cloth down there. I did some tests with data loggers and frost cloth and found while it was enough up here, it only kept them slightly warmer.

https://m.youtube.com/watch?v=x5Pf_n86cZI&t=3s

Firstly, great video, and good to see another Aussie on here. I love data driven information that shows empirically how much of a difference cold measueres make in the wild.

Secondly I thought that the difference provided by your (much thicker) frost cloth was quite sigificant. I bet in colder temperatures this difference would be even more pronounced.

Unlike your trees mine are on concrete pavers, with some right up against the brick wall of the house. These should act as a heat sink much like the water container with your jackfruit. The pots themselves are mainly black and should also absorb some heat during the day and hopefully radiate through the night. 

Although the frost cloth is quite thin, I have purchase 4 strands of 300 xmas bulbs which I will wrap around the pots and stems, and should radiate even more heat upwards overnight.

Here is an idea of what I have undercover https://www.youtube.com/watch?v=zVRIRDRf8FU, not quite as well put together as your own, but we do what we can!

Thanks for the kind words. Really keen to see how it goes with your trees. You are certainly right that the concrete/brick walls will hold heat, a lot more than my barrels of water. You might indeed get enough buffer to avoid damage in the lows at which point (as others said) it’s the lack of heat during the day that’s the challenge.

[850FL]

Also a few more factors at play- higher humidity seems to worsen the effects of freezes. And plants established in the ground often seem to do better than plants on the ground in pots (even if many survive they eventually may need big bulky pots to produce a decent amount of fruit anyway).
Also sometimes frost coverings may trap too much heat and end up conversely killing your plants.. especially if say it was 35 degrees F and then the sun came up and warmed inside the covering to 90 degrees- thats almost a 60 degree temp swing in a short period. The point is just monitor the covering when the sun gets more intense.
And even just a single drop to -6 or -7C can mean disaster when certain plants were just fine during -2 and -3C frosts. You had a sapling hass survive -6 or -7C with barely any stress? I had probably 10 seedling/sapling hass and ALL were stumped when it got to -7C.. one was even 8ft tall and not lanky either!

[naikii]

Also a few more factors at play- higher humidity seems to worsen the effects of freezes. And plants established in the ground often seem to do better than plants on the ground in pots (even if many survive they eventually may need big bulky pots to produce a decent amount of fruit anyway).
Also sometimes frost coverings may trap too much heat and end up conversely killing your plants.. especially if say it was 35 degrees F and then the sun came up and warmed inside the covering to 90 degrees- thats almost a 60 degree temp swing in a short period. The point is just monitor the covering when the sun gets more intense.
And even just a single drop to -6 or -7C can mean disaster when certain plants were just fine during -2 and -3C frosts. You had a sapling hass survive -6 or -7C with barely any stress? I had probably 10 seedling/sapling hass and ALL were stumped when it got to -7C.. one was even 8ft tall and not lanky either!

The Hass I didn't expect to survive actually. I bought it as a duo type A and B, with a Bacon. I only really wanted the Bacon, but the special was cheaper than buying the Bacon alone. I put it in a approximately 34L pot and didn't do anything except move it under cover. Surprisingly it didn't seem to be affected at all.

The Bacon I put in a sheltered position in the garden, and it pulled through with minor leaf damage. It was however a warm winter last year.

I've had to go interstate for a week right now and watching the weather we have a -4oC morning predicted the day we get back. I had hastily draped some frost cloth just in case before I left, but barely secured. I had to run at very late notice.

The containers that these trees are all in are general quite large, 30L and 55L mainly. Some 85L and a couple in 10L containers.

I hope I'm not in for a shock when I return after this cold morning, no chance to put the Christmas lights up yet.

[CarolinaZone]

I forgot to mention I have an in ground strawberry guava. I used minimal protection on this other than covering the base with leaves. 3gal planted last year in the spring. The exposed branches are pushing growth now.

[850FL]

I forgot to mention I have an in ground strawberry guava. I used minimal protection on this other than covering the base with leaves. 3gal planted last year in the spring. The exposed branches are pushing growth now.

Which strawberry guava? P. cattleyanum?

[CarolinaZone]

As far as I know P. cattleyanum is the only strawberry guava. Is there another plant called that?

[brian]

I think the yellow type is psidium littorale, even though it it basically identical to the red kind other than the fruit color/taste

[CarolinaZone]

Ok. Well here's where it get's interesting. To be honest I am not sure but I Suspect it is a cattleyanum var. littorale. I had bought several the year before last that were marked incorrectly as red cattley guava P. cattleyanum var. cattleyanum. Later last year when one of them fruited it was yellow. I suspect the one in ground is from that batch.  It defoliated over the winter and some of the branch tips have been damaged. I plant to pull back the mulch and fertilize heavily. Only the new growth seems to be damaged. The woody mature growth seems ok. The issue I see is the two flowering cycles. Cycle one seems to start in October and cycle two seems to start in  February. Cycle one is too late for the fruit to mature before it get s too cold. Cycle two ( this based on the indoor specimens) would be two cold for the fruit to appear outdoors.

[naikii]

Well a frost and cold night had been predicted and the tropical-fruit-gods themselves must have been angered by my audacity at trying to grow these tropicals because they sent a reckoning.

We had one of the coldest May nights on record, still several weeks out of Winter reaching a shocking -5.4o C (22.28 F). Not only one of the coldest days in May's history, the coldest minimum in over 2 years, with the low of last year's winter not getting this cold (very warm winter though).

Compounding the joke, I had an emergency trip planned interstate. I had hastily draped the plants with some frost cloth without much in the way of anchoring without too much concern as both a mild and still week had been forecast. Obviously on my return (later on the same day of the severe frost and chill) the frost cloth had all but blown off everything.

I am taking stock of damage. Surprisingly most seem as I left them. There are some exceptions. Here are some of the highlight and lowlights.

Bananas; older leaves are quite browned on large trees. Not killed through, they are languishing a slow decline. Younger new shoots still are green and pushing through. Young treees are suffering a little more, one in particular looks troubled.
Babaco: Supposedly one of the hardier of my plants, it has been hit the hardest with many leaves instantly nuked. The damage looks enough to recover from potentially, but only time will tell. I estimate 1/2-3/4 of the plant will defoliate. 
Lychee: Looks to be mildly upset. SOme leaf discolouration and damage, some of which had happened before I went away.
Jaboticaba: One seems a little mad and some leaves have turned purple. Whether dead or just seasonal time will tell. Other Jaboticaba do not seem affected in the same way.
Carambola: Doesnt look grand. It is hard to tell if the frost cloth rubbed some leaves off or if it is suffered from the cold.
Rollinia: I have a few. Some look ok, some look like they are about to give up on life.

Champions at the moment:
White sapote: I have around 5 plants. Several are still pushing bright new green growth as if they were in the tropics, some seedlings (50-100cm tall) are showing some leaf distress, which has been creeping up over a week. Cannot see any acute cold damage from the other night.
Cherimoya: Looks how I left it. That is a win in my book. New growth, no damaged leaves.
Longan: Pushing new growth, cant see any damage.

Most others in the collection very little to report and are still ticking over just fine. Cold is a little insidious though, sometimes the damage comes a day or so later.

And because pictures speak even more words than me;

Babaco in pain



White Sapote no problems



Cherimoya just chilling



Bananas hanging on

[naikii]

Since returning I have also set up some wireless sensors to monitor the cold protection provided. My goal is to map out the hot and spot areas and use them to help get through the next few months and to test different cold protection methods.

I had additionally purchased 1200 incandescent christmas lights which I dutifully strung throughout all the plants, only to have the cheap damn things all die after several hours. Now I have the fun job of removing all those lights and sending them back.

Over time I will post how much protection each of the areas under the patio provides. I have attached a crude map to show the location of each sensor.



I have 5 in total;

• Sensor 1, towards middle of patio with no frost cloth, and a decent amount of brick wall adjacent as well as eaves of house. In an Achacha Pot resting on soil.
• Sensor 2, towards the edge of the patio with a frost cloth covering, no walls in close proximity. In a White Sapote pot resting on soil
• Sensor 3, towards the edge of the patio with no frost cloth covering, against a wall and under eave. In a Hass avocado pot resting on soil.
• Sensor 4, control sensor outside of the patio area away from walls of hosue. In a very large (300L pot) with a Tangello.
• Sensor 5, soil temperature and moisture under frost cloth. In Cherimoya pot.

The patio provides several degrees of protection.

Local weather is being reported now as: 12.4o C. Current reported temperatures from sensor readings are;

• Sensor 1, 14.0o C.
• Sensor 2, 13.0o C 
• Sensor 3, 10.7o C.
• Sensor 4, 6.7o C.   
• Sensor 5, 7.7o C.   

The overnight minimum was reported as -3.1o C. The minimums recorded from the sensors was;

• Sensor 1, (null, needed resetting).
• Sensor 2, 1.0o C 
• Sensor 3, 0.1o C.
• Sensor 4, -1.3o C.
• Sensor 5, 4.7o C.   

Current soil moisture is at 47%.

[Fygee]

Similar story in Las Vegas where I live.

Winter temps tend to be the death knell for a lot of tropicals/subtropicals. I either bring the smaller ones indoors, or protect them with burlap in a corner that stays just a bit warmer than the rest of my yard.

Some of my trees like my avocados and mangoes handle winter unprotected just fine now, primarily due to our winters being warmer than usual lately. That said, we had a freak snowstorm this year that took out my Coconut Cream mango tree that I'm very sad about. Weirdly enough, it wasn't the snow, but the melted snow waterlogged it and it got root rot.

Anyways, it can be done, but protection and variety selection are very important.

[naikii]

I love hearing stories about people succeeding with these cold protection measures, makes me feel there is hope. Did your Mango and avocado trees fruit?