Pancrazio

I wanted to share with you the results of this experiment, because for ages i have been searching exact data on cold hardiness of bananas, and while the general elements are well know (this is hardier than that) when it comes do to put down exact values, i did find hard to get a precise picture on how hardy a banana could be.

To do this experiment i choose a dwarf namwah; while it may not be the hardiest among all, it is still a very vigorous plant, people tell me it also fairly productive, I personally noticed that is very resistant to several stresses, and it is, in my opinion, the best subject, overall, for someone willing to grow bananas in a zone where bananas aren't meant to grow.

Before this experiment my method of growing bananas has been this one: i planted my bananas in ground on 1st of April (I think the neighbors thought about a joke the first year i attempted this) and potted them up at September. I did this for several years, and i did get several pup in the process; some of them have been kept for testing purpose.

Once i managed to get a pup big enough, i did grow it to a decent size (5') just to attempt this experiment and I did plant it in ground hoping to overwinter i: following some suggestion on bananas.org, i did plant it fairly deep.
During all the summer i attempted to push it at the best of my possibilities, hoping that the sheer size of it could help to offset any physiological problem due the nigh level of nutrients.

This was the plant in April 2015, and next the plant in October:


Long story short, the plant arrived in perfect condition to the end of November, where we got out first cold damage: at the relatively high temperature of 3°C (that is 37F) the plant started to show some damage:




But overall the plant held very very well for all the winter; pretty much at Christmas it was still in a good overall shape:



When you get a winter so warm, you can't avoid to be happy for your plants, but, in the meantime, you are well aware that no new knowledge is being made; it wasn't surprising to see a Dwarf namwah doing well with temps regularly above the zero/32F.
Luckily, i January we got something that was normal till few years ago, but right now looks pretty unusual: a cold spell.

At first it started slowly: on the night between 16 and 17 January we got -2,4°C (27,6F):


The following night we went to -3,7°C (25,3) with ice starting to form in water left outside:



On the 20th the temperature reached -6,1°C (that is 21F) with extended damage on the entire plant/pseudostems:

You can see the "washed away look of the tissue cooked by the low temperatures:


The next day the temperature reached the absolute minimum at -6,4°C (that is 20,5°F).


As you can see from this graph, we got an extended period of time (about ten days) with night dripping regularly in the low 20s;

During all this time the plant never had any other protection than the one due the planting location. I wrapped it in frost cloth at the end of the frost spell - the reason was that i feared new cold spell but we didn't get any. Admittedly, i didn't planned to get so much cold for my experiments: so i wasn't really prepared but on the other had, i also think that if you wanna grow something outside its zone, you've got to choose what is worth an extra mile (in my case, mango) and what isn't (bananas); i like bananas, but i can't give to all my plant the lever of care i give to my mango, so they had to deal with difficulties themselves: on a multi.year perspective, this is the only way i can hope to grow plant in a sustainable way.

Well, at this point you have seen what the have been trough. They are dead right? RIGHT?
WRONG!




Few days ago they showed unequivocally that they are sill growing: so, except the damage to the most exposed leaf sheets, they didn't even lose the pseudostem. The picture is already old and the smallest plant has almost finished to unfurl its first leaf.
This may not be a surprise for some of the most expert zone pusher out there, but for me it was quite a surprise.
So i think that a couple of thing can be said from this small experience i have done; Dwarf Namwah can be a interesting banana to grow for beginners and zone pushers, and they can survive pretty well to temperature in the low twenties.
I hope this may help someone undecided on what bananas may do well in its place.
I'm well aware that a surviving bananas is pretty different from a fruting bananas, but the latter can't be achieved without the former, and dwarf namwah seems the best bet in my opinion.
(For the record: dwarf orinoco did better than dwarf namwah in cold environment, but is slow and not very vigorous, and i have an hard time convincing it to grow. And fruits at my place apparently take forever to ripen.)

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hydroid

Very nice bananas. Dwarf namwah is my "go to" banana for a good yield of fruit in my zone (8b/9a). I put chicken wire around it and grass clippings then wrap in plastic in Dec. Then unwrap in the spring. It gives them a head start on the growing season. They have the best potential to fruit compared to my other varieties, plus they taste pretty good too.

siege2050

Wow, in the 20's F?

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Pancrazio

Hi hydroid, I think it's a great banana too. Not to mention how well it handles the lack of water/dry stress.

@siege2050: yep thats right. Incredible right? Never hoped to have it respond so well to cold spells. It gives really hope that it may fruit reliably for me even in my zone.

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crazy banana

Nice experiment and good job documenting it.
I love my "old faithful" reliable dwarf Namwah. Fruits every year and the bunches get bigger every year, too.
It would not surprise me if you will see an inflorescence on your plants soon.
Your experiment is interesting and possibly helpful for other members with marginal climates. One thing to take into consideration though when talking about cold resistance is to look at how long the plant actually was exposed to the cold. Here in San Diego I had four mornings in December with about two hours each were the temperatures dropped to 28F. All my plants looked similar than yours. However, I think if the temperatures would have been that low consistently over a longer period of time (days or day and night), the plants and especially the p-stems would be in worse shape if not completely destroyed.

gmichael403

Great write up..very well done!

Pancrazio

I really hope you are right. I have been growing dwarf namwah fro 4 years now, and they did take some effort, especially since, till this year, every year i have had to remove the whole plant a store in my greenhouse. Now i hope to leave mein outside all winter, thus saving a far quantity of work. I'll probably just save a pup at the end of every summer to be safe in case we get one of those nasty winter where we can reach 14F.

I think you are right. We got till 20,5F during night but during the day we got 45/50F. If i has 25/28F constantly for ten day i'm relatively sure i would have lost the pstem.
Another thing I want to add is that, since i hoped to increase to the max the hardiness of the mat, i didn't prune any of the stems. This should have had the following effects on the plant:
1) Reduce the physiological stress that any pruning brings, even if necessary
2) Increase the hardiness because between more stems there's more heat trapped/less air circulation/less radiating heat and so on.
3) Last but more importantly: several stems do produce bunches on an extended period of time; and smaller bunches being produced continuously is the way to go for someone living in a place where winter destroys any ripening bunch: because it increases the chances to have a flower to emerge when the moment is "just right" for the bunch to have several months to ripen.

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Grannycore

I completely agree. I left some out this winter as sort of an experiment - I wrapped and bundled three six-foot trees to see what would happen. Our lowest low was 17, but we got extended periods where it was in the twenties, and the only ones with any p-stem survival was dwarf Orinoco and California gold. The other ones were frozen mush to the ground. So our lows weren't substantially different, but I had a significantly longer amount of time below freezing, and it happened repeatedly over 2.5 months. I definitely (and unfortunately) would not have these results.

asacomm

Hello Pancrazio,

An extremely exciting report!! Congratulation too!
I am very much interested in how the plant developes to grow with what
kinds of handicaps or damages.
So I do expect your further reports from time to time.

Thanks in advance.

crazy banana

I have mentioned it before, but one other important point is to start out with the best, healthiest plants possible before going into the cooler winter month with less daylight. Cannot do anything about the shorter days, but I believe that feeding your plants some extra potassium by the end of summer or early fall will result in stronger cell walls of your plants and subsequently add some cold resistance.

PR-Giants

Great job, Pancrazio

Thanks

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Pancrazio

I see what you mean. Acute and extended damage are definitively two different things. I think that the key point is to have at least some daily temperature above 32F. I think that ice started forming inside the plant but wasn't capable to do too much damage because during the day it unfreeze.
Also, i'm interested to see the other thing you point out: how well the plant behaves when there are several cold spell over 2-3 months.
This year we got just this cold spell, and it is pretty unusual for me (we get usually several during winter); but i'm happy because this way if in the next years i get some damage from several cold spell in row, i can tell for sure that it isn't the single cold spell doing most damage, but the sequence of cold events.

Hey asacomm, I'll do it for sure, I always have read your post on the way you used to overwinter your plants with great interest, it's time to reciprocate.

I do agree with that, in fact at the end of July i stop any activity on the plant that could result in a stress, so they have 4 months to completely recover. Worst thing is de-suckering: stopping it during the 4 months of most active growth can result in a seriously overcrowded mat, and to be honest, i still don't have a clear idea on how i should deal with suckers for that plant. I just know that i'm hoping for a crowded mat.

Thank you Keith!

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Grannycore

[quote=Pancrazio;284285]I see what you mean. Acute and extended damage are definitively two different things. I think that the key point is to have at least some daily temperature above 32F. I think that ice started forming inside the plant but wasn't capable to do too much damage because during the day it unfreeze.
Also, i'm interested to see the other thing you point out: how well the plant behaves when there are several cold spell over 2-3 months.
This year we got just this cold spell, and it is pretty unusual for me (we get usually several during winter); but i'm happy because this way if in the next years i get some damage from several cold spell in row, i can tell for sure that it isn't the single cold spell doing most damage, but the sequence of cold events.



Hey asacomm, I'll do it for sure, I always have read your post on the way you used to overwinter your plants with great interest, it's time to reciprocate.



I Plan on posting my results in about two weeks, when any threat of cold temperatures are done and I gave enough growth to report success...I experimented with many things - some things left totally unprotected, wrapped trunks on others, some lifted and pitted and cold stored in a garage, and some cold stored barefoot. I will definitely know what I want to do next year! We don't have cold winters here compared to most of North America, but we have enough winter to matter. Looking forward to a move to Florida in a year or two.

37.667910

Thanks a bunch! (no pun intended)
I'm convinced...Think I'll give these a try here in my 9B climate!

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Pancrazio

Here's the first update: the plant is about to unfurl a second leaf on one of the less damaged pstems:




Most interesting, for me is the fact that the Dwarf Orinoco at about 2 feet from the dwarf nawmah appears to be dead. But the jury is still out on this one:

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asacomm

Buon georno, Pancrazio,

Thanks for the update of your bananas. It seems also for me that the
Orinoco is dead.
Do you know why the Orinoco failed to overwinter while the Namwah
succeeded in overwintering on the same environment?

Pancrazio

Honestly? I don't have the slightest idea.
The D. Orinoco should be a tiny bit hardier than the d. namwah. Still, it managed to die, despite being in pretty much the same place. My best guess is, that since the Orinoco itself was a bit smaller, it was also more tender. But it's just a guess.
For sure the bi pstem of the dwarf namwah must have given some kind of insulation because right now the cold damage parts are peeling of revealing an healthy (albeit smaller) pseudostem.

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Pancrazio

Second update.



Dwarf Namwah is quicker to recover than i thought, showing on the most advanced stem already 2 leaves, and putting out the third. By comparison, the plants (dwarf namwah) that i overwintered by uprooting them haven't put out not a single leaf yet.
At this point i can say that every stem has resumed its growing, but the growth appears stunted on every stem. I think i will take about a month before i can see new healthy leaves.
At the moment new leaves are almost white, probably due the damage of cold temps. The leaves of the stem at the left of the picture have problems unfurling.
Stems are way less thick than when i started the overwintering and i don't know how this will impact flowering/if it will impact flowering. However they shed all the dead layers outside and the appear reasonable healthy for the season.

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Pancrazio

One more update. No pics this time.
Banana appear to be growing on all the stems.
Bigger stems are the slowest recovering from damage, while smaller ones appear already healthy.
The stems with the biggest number of leaves have shown the following behavior on new leaves:
1st leaf: Strong; normal sized, but heavily damages by cold
2nd leaf: Strong; from completely normal, to "less than normal sized" but overall in good shape
3rd leaf: Weak; pale leaf. On some stems this is chocked in the previous leaf, on some other stem it's just a very short and narrow leaf apparently underdeveloped and undernourished. Maybe it was the leaf "in the making" when the frost did hit?
I think that next leaves should be normal. But it remain to be seen. Biggest stem, the one i hoped to see flowering this season, has to emit its first leaf yet.

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maesy

Hi Pancrazio

I suspect the smaller stems are stealing the energie for new growth from the mother plant to ensure their survival. Thats why the mother stem is behind her kids. I still hope for you there is a flower coming up in early summer.

Marcel

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