Frost-hardiness limits of a range of Mediterranean & Subtropical Fruit Trees

While reading a book entitled Citrus & Subtropical Fruits (2nd edition, Meredith Books 2008), I came across a range of subtropical fruit tree species, some of which appear to be significantly more frost-hardy than I would have imagined.  I have a natural interest in this area as, during my working life, I have carried out research examining the adaptation of plants to stressful environments.

Intrigued by what I read, I thought I would list the data, given by the above book, on frost-hardiness. I would like to pass on this information to you for two reasons. First, the information might be useful, if you have an interest in growing subtropicals, and second, it might stimulate some discussion of any successes or failures that you may have had, trying to grow some of these species.

The data below shows the limit of cold-tolerance for mature trees. Seedlings, young trees and fruit are normally more cold-sensitive. Latin names for the tree species are given in parentheses.

  0°C  (32°F)       Coffee, (Coffea arabica)
–1.6°C  (29°F)     Cherimoya (Annona cherimola)
                           Navel Orange (half-ripe fruit)
–2.2°C  (28°F)     Pineapple (Ananas comosus)
                            Limes
–2.7°C  (27°F)     Lemons
–3.8°C  (25°F)     Lychee (Litchi chinensis)
                           Mango (Mangifera indica)
–4.4°C  (24°F)     Strawberry guava (Psidium spp)
                           White Sapote (Casimiroa edulis)
                           Grapefruit & Oranges
                            Avocado grown from store-bought fruit (based on my limited outdoor trials)
–5.0°C  (23°F)     Mandarins (generally)
–6.6°C  (20°F)     Carob (Ceratonia siliqua)
–7.7°C  (18°F)     Satsuma (fully dormant)
–9.4°C  (15°F)     Pineapple guava (Acca sellowiana (Feijoa])
–11.1°C (12°F)    Fig (Ficus carica)
                            Olive (Olea europaea)        
                            Pomegranate (Punica granatum)
–12.2°C (10°F)    Kiwi (Actinidia deliciosa)
                           Loquat (Eriobotrya japonica)
–17.7°C (0°F)      Persimmon (Diospyros kaki)  
–23.3°C (–10°F)  Raisin tree (Hovenia dulcis)
–28.8°C (–20°F)  Che (Cudrania tricuspidata [=Maclura tricuspidata])
                            Jujube (Ziziphus jujuba)              
                            Paw Paw (Asimina triloba) - NB: don't confuse this with Papaya (Carica papaya)

that’s a nice little list. there are a couple of things where i’d push the numbers a little further: figs can easily live through 0F or lower, but they freeze to the ground. if you have a good variety that fruits on new wood, you can still have fruit every year. i’ve left my potted loquat out all through this winter (it occasionally dropped to single digit temps) and it seems fine (won’t get fruit though, because they bloom late autumn/early winter). for kiwi, there are species (at least A. arguta and A. kolomicta) that are hardy well below those numbers - i think i’ve seen -40 (C and F!) quoted for kolomicta. and pawpaws are a solidly temperate tree. they have many tropical and subtropical cousins, but it’s not surprising that they are relatively cold-tolerant themselves.

I'm interested how hardy pomegranate appear to be. I wonder why I haven't seen them more in the UK then? I suppose they need hotter summers to fruit well, but in my polytunnel....Hmmm!

greg mosser wrote: there are a couple of things where i’d push the numbers a little further:
- figs can easily live through 0F or lower, but they freeze to the ground. if you have a good variety that fruits on new wood, you can still have fruit every year.
- i’ve left my potted loquat out all through this winter (it occasionally dropped to single digit temps) and it seems fine ...
- there are [Kiwi] species (at least A. arguta and A. kolomicta) that are hardy well below those numbers ...
- pawpaws are a solidly temperate tree ...

Thanks Greg, you've raised some really good points.
I would say that the temperatures quoted from the book are to be taken as a very rough guide only, as there will always be cultivar or varietal differences within a species. Also, the information is incomplete in that it doesn't indicate how long the different tree crops can endure the temperature limits given. Furthermore, I think these data represent the limits for the above-ground parts to survive cold weather.  This is important if you want your tree to grow to any decent size.  If it's razed to ground-level most years by freezing temperatures (e.g. like the fig you mention at  0°F, resprouting from the base in Spring), the tree will never achieve a decent size, and some tree species are likely not to fruit as a result.

Potted Loquat - difficult to comment as a lot depends on how cold it was in the local environment where the tree was: was it in a sheltered position, e.g.  against the wall of the house, surrounded by other trees, etc ?

Actinidia arguta (–10°C), A.kolomicta (–15°C): these are only conservative estimates and you'll find significantly lower temperature limits quoted elsewhere, which may well be correct. Thanks for the Kiwi comment, as it meant I edited the list, changing Actinidia spp. to A. deliciosa for clarity !
 
Pawpaws - yes you're right, A. triloba is solidly  temperate !  I think it was included in the book as it appears somewhat exotic (unusual) in nature, rather than it being a warm-climate species.

Nancy Reading wrote:I'm interested how hardy pomegranate appear to be. I wonder why I haven't seen them more in the UK then? I suppose they need hotter summers to fruit well, but in my polytunnel....Hmmm!

You've hit the nail on the head, Nancy - though cold hardiness may not be a problem, I don't think our U.K. summers are always hot enough for long enough for good fruiting.  You might be in with a chance in the polytunnel though, but  the height limitation might be a problem.  I have a friend who keeps a peach tree (quite an ancient one now) in his polytunnel - it fruits every year but he has to prune it within a couple of inches of the plastic covering.  It's almost like a large bonsai, with a fat stocky trunk. Can pomegranates be espaliered (?) - if they can, maybe it would be another way for you to get around the height limitation ...

Mike Guye wrote: I have a friend who keeps a peach tree (quite an ancient one now) in his polytunnel - it fruits every year but he has to prune it within a couple of inches of the plastic covering.  It's almost like a large bonsai, with a fat stocky trunk..

Yes, I have an apricot in my tunnel. The cover is shredded just now which is unfortunate because a) the tree is covered with blossom which will have no protection from the weather and b) this was to have been it's last chance year to give me fruit. I got quite a few fruit set in 2020, but they all dropped before they were ripe. I think they need a bit of help with pollination - not enough insects around inside the tunnel at this time of year. But I'm not sure why they fell off. The tree is much more vigorous than I expected and I'm getting suckers coming up from the rootstock.

A Pomegranate could be just the thing to replace it with. If you prune it more like an apple it would be easier for me to prune. I'm always wary of pruning the apricot in case I kill it, but it is one of the reasons the plastic need replacing: it punched its way through when I wasn't looking.

The only times I've picked pomegranate off the bush, it was a bush, not a tree. In the range of 4-6 feet tall. Looking online, I see that they grow to be trees that wouldn't fit most hightunnels, but that's not how I've ever encountered them. (I wonder why, now.) Anyway, shortish bushes can produce quite a few fruit, so I bet it's a good fit for what you guys are describing.

I planted ~140 pawpaw seeds last winter/spring. They germinated slooooowly, but by fall, I had lots of tiny trees in air-prune beds. They're out in a nursery bed now, surrounded by three-high hay bales and under an inch of hay and 14 inches of snow. It'll be interesting to see if any of them survive into the spring. I think our low this winter so far has only been -28F (-33C), so not as cold as some years. It's a big push from their native range, but would be really exciting to get a few that work out.

Nancy Reading wrote: A Pomegranate could be just the thing to replace it with. If you prune it more like an apple it would be easier for me to prune. I'm always wary of pruning the apricot in case I kill it, but it is one of the reasons the plastic need replacing: it punched its way through when I wasn't looking.

Could a dwarf pomegranate be the answer?  When in stock you can buy it here:  https://www.victoriananursery.co.uk/Dwarf-Pomegranate/  though there are probably other outlets too.

Hardy kiwi fruit (A. arguta) have been hybridized with A. deliciosa.  It would be wonderful to see folks working with these hybrids to bring zone 4 hardiness to the resulting population.  Anyone know of anyone aiming for that in their breeding work?

Update:  Here's one breeding effort in the US:  Hardy Kiwifruit Breeding Project

Mike Guye wrote:
Could a dwarf pomegranate be the answer?  When in stock you can buy it here:  https://www.victoriananursery.co.uk/Dwarf-Pomegranate/  though there are probably other outlets too.

It could be the answer, but I've heard that the fruit are miniature too, and pomegranate are already a bit of a faff to peel....

My fig has survived -18C with no die back at all. I haven't seen any damage on any other figs either. They are of course all planted in sheltered locations. I know someone here that has an apricot in a "Pollytunnel" it's a dome so there is a bit more height but I think they keep it pruned to about 2m tall. I have just bought an apricot, I don't have high hopes as it will not be getting a southern facing wall, but I have space for a tree to just lurk if that's what it wants to do.

Nancy Reading wrote: It could be the answer, but I've heard that the fruit are miniature too, and pomegranate are already a bit of a faff to peel....

When eating normal-sized pomegranates, I've never peeled them, just cut them in half and eat the seeds by scooping them out with a spoon. I thought it might be the same with the mini ones ...

Skandi Rogers wrote: My fig has survived -18C with no die back at all. I haven't seen any damage on any other figs either. They are of course all planted in sheltered locations

As it was sheltered, don't you think it was probably significantly warmer than –18°C, immediately around the plant?  That said, Skandi, it's great you can grow figs at 57° latitude !

Mike Guye wrote:

Skandi Rogers wrote: My fig has survived -18C with no die back at all. I haven't seen any damage on any other figs either. They are of course all planted in sheltered locations

As it was sheltered, don't you think it was probably significantly warmer than –18°C, immediately around the plant?  That said, Skandi, it's great you can grow figs at 57° latitude !

No I suspect it went all the way down, I don't see how it wouldn't have we had that temperature for nearly 24 hours and no sun. But it wouldn't have gotten any wind or damp which is what does the damage. Not only do they grow here but they fruit as well. It was planted 2 years ago and last year (after that frost) I got 5 figs. very happy with it. The cold snap burst pipes that were over 1m down under our barn.
I've found it's not the cold plants can't handle but the damp and wind, I couldn't keep rosemary or sage alive in the last house and it only went to -10C I might try them here since I seem to have a better spot for overwintering things.

Skandi Rogers wrote: ... I suspect it went all the way down [to –18°C], I don't see how it wouldn't have we had that temperature for nearly 24 hours and no sun.
... I've found it's not the cold plants can't handle but the damp and wind, I couldn't keep rosemary or sage alive in the last house and it only went to -10C I might try them here since I seem to have a better spot for overwintering things.

.
Sheltering from the wind can make a big difference to temperature, e.g.  wind is the main factor for heat loss from greenhouses.  Also, for example, planting shelter-belts (e.g. hedges) around crops in exposed locations, can act as a thermal buffer by reducing wind-speed.

Yes, that's really true what you say about damp (wet soil) during winter - wet soil combined with low temperatures can cause a lot of winter damage, especially where drainage is poor, and is certainly the case for those Mediterranean herbs you mentioned.  Nevertheless, the resilience of your fig is remarkable - sometimes plants can really surprise us with their behaviour ...

I've got some cuttings of a fig that allegedly was fruiting on the mainland near me as well at about the same lattitude as Skandi. They're not looking too good at the moment, but I'm hoping at least one of them will take....
I have some small rosemary and sage plants that have survived a couple of winters here - planted on the top of my driveway retaining wall, so well drained and sunny. As you say it seem to be the damp soil that is the worst in our climate. Skandi's winter is a bit colder however.

In the foothills of where I live, many oranges lemons and limes grow to maturity and produce abundant fruit every year even where it gets down to 22-25F sometimes. Much potential with seed-grown trees, even if one can't get their hands on special cold-tolerant varieties!

Jonah Bassman wrote: In the foothills of where I live, many oranges lemons and limes grow to maturity and produce abundant fruit every year even where it gets down to 22-25F sometimes. Much potential with seed-grown trees, even if one can't get their hands on special cold-tolerant varieties!

That's really interesting Jonah - some Qs:

- You mention seed-grown Citrus trees; are the trees in the foothills self-seeding ones in the wild (not cultivated)?
- What's the winter rainfall like in the foothills?
- Is it sheltered, or very windy?

I'm just trying to get an idea of what other environmental stresses these trees are having to put up with, in addition to the freezing temperatures you mentioned.

Mike:
-It's hard to tell which are and which aren't, as virtually all of em are at the houses/ranches of folks I don't know, but I know at least a handful of seed-grown citrus do well up there! But it would be started in pots by people from their own seeds or compost- none appear to be any truly wild type, and there aren't any native citrus to this area. Many are surely from local nurseries, but even then, I believe "regular" (not super cold hardy) varieties still do well even in the areas where it gets to 22-25 lows sometimes.
-Rainfall gets anywhere from 10-20 inches (avg is written of as being around 22 inches but certainly gets below that regularly since I've been around). Very little of that is snow, for what it's worth; usually just a light dusting per year compared to most areas. The central valley which is lower in elevation never gets any snow.
-Lots of these areas are actually fairly sheltered-- driving through this area, there are many tiny valley type areas with plentiful evergreen oak/pine for shelter, and where there aren't valleys, hillsides have those same nice diverse sheltered conditions as well. I know this creates some great microclimates where bending the rules hardiness-wise seems much more doable than the mountainous areas of other places/higher in our mts.

Elevation on these drives where I see the most citrus in yards/ranches higher than the valley floor (which is about 308' above sea level itself) tends to be between 1000 and 2000 feet, for what it's worth. I love to see people pushing the known limits and getting away with it.

I live at 3000ft in the foothills. It was 20F this morning but that's about as cold as it gets here. I would love to grow lemons! Maybe lime too cause I love mojitos. My neighbor does but they are on wheels and go into a greenhouse for the winter. I wonder if I could baby them for 3 years and then plant them in a smart spot and get away with it? I used to think the answer was "hell no" but this post is making me want to get crazy!

Dan Fish wrote:I live at 3000ft in the foothills. It was 20F this morning but that's about as cold as it gets here. I would love to grow lemons! Maybe lime too cause I love mojitos. My neighbor does but they are on wheels and go into a greenhouse for the winter. I wonder if I could baby them for 3 years and then plant them in a smart spot and get away with it? I used to think the answer was "hell no" but this post is making me want to get crazy!

Hi Dan - Satsuma would be a better choice for a cold-hardy Citrus tree that produces really tasty fruit.  On the right rootstock (e.g. Poncirus trifoliata), mature trees are reputed to be frost tolerant down to  −8°C (17°F) or lower.

Mike Guye wrote:

Dan Fish wrote:I live at 3000ft in the foothills. It was 20F this morning but that's about as cold as it gets here. I would love to grow lemons! Maybe lime too cause I love mojitos. My neighbor does but they are on wheels and go into a greenhouse for the winter. I wonder if I could baby them for 3 years and then plant them in a smart spot and get away with it? I used to think the answer was "hell no" but this post is making me want to get crazy!

Hi Dan - Satsuma would be a better choice for a cold-hardy Citrus tree that produces really tasty fruit.  On the right rootstock (e.g. Poncirus trifoliata), mature trees are reputed to be frost tolerant down to  −8°C (17°F) or lower.

Yep. I have some Owari Satsuma grafted onto Trifoliate rootstock that is supposed be hardy down to 12F after it gets mature (4 or 5 years).

Which, since I have it in a microclimate and 12F would nearly be a record cold in my area, then it should do well where I planted it a few days ago. I will be throwing a plant jacket and Christmas lights on it for those super deep nights for the first few years though.

I also want to get a few Yuzu lemons out there. They are supposed to be good down to 5F.

EDIT:
Here is a link to a chart of cold hardy citrus types. It looks like Yuzu is rated to 10F.

However, there are even more cold hardy types if desired.

http://hardycitrus.blogspot.com/2014/01/cold-hardiness-table_13.html