Are there any high-altitude tropical areas that have trees that can tolerate severe frosts? I know the chinaberry trees is from India and Southern China but can be grown in zone 7.
Mexican White Pine Pinus ayacahuite is by far the best example - native to the mountains of Mexico and Central America at 14° to 21°N latitude (entirely within the tropics), but with some origins hardy down to -30°C. There's mature specimens of it growing happily at 56°N in Scotland, a full 35 degrees of latitude north of its native range. In USA, there's a specimen growing in the Masonic Homes Arboretum in Elizabethtown, PA (1979 article; and still present 2018).
Ok thanks for the info. Never knew about this pine till now. Are there any other species like this? I know Sapindus mukorossi is one of them that is native to tropical regions in Asia but can be grown in temperate places.
Pinus hartwegii and Abies religiosa also grow at high altitudes in tropical Mexico, but haven't proved as hardy as Pinus ayacahuite in cultivation.
Are there any broadleaf evergreen or broadleaf deciduous trees like those that tolerate those conditions or likewise?
Natural ranges of various frost tolerant eastern North American native deciduous trees continue south of the border with Mexico, sometimes well south. For instance Acer negundo occurs in Mexico and Guatemala, as does A. saccharum; Carpinus caroliniana ranges down into Mexico and Central America, and Nyssa sylvatica extends as far as S Mexico.
Tropical maples formerly included in Acer saccharum have been split out now as Acer skutchii (SE Mexico & Guatemala) and Acer binzayedii (Jalisco, SW Mexico). How hardy these taxa are, I don't know, but relationship to temperate taxa doesn't necessarily make them hardy. I'd not be surprised if the other examples get split in the future, too.
I know some Himalayan trees do good in some cold climates that are evergreen- Lithocarpus and various evergeeen Quercus from Central China south to the rest of Asia.mm2
Some enthusiasts grow avocados here. Me too, my tree is 3 years old and I dig it out for wintering, but I know a person, who has much older tree permanently in the ground. Of course, he covers the tree for winter. But he is in the zone 5/6, that's colder than original poster of this thread (Atlanta, 7B/8A). https://www.gardeningknowhow.com/edible/fruits/avocado/cold-tolerant-avocado-trees.htm
Original poster has not actually stated specifically that they are looking for tropicalissimo style trees to try growing in Atlanta. Or even what their idea of "severe frosts" consists of. With the result that the discussion has not so far had a well focused and consistent topical sequence.
Yes, but remember the tolerance figure of -7°C cited at that link can be reached in a zone 9, even zone 10 winter: the zone figures are based on average winter minima, but it is extreme winter minima that kills tender plants. I'm on the border of zone 8/9 (average annual minimum about -7°C), but in a severe winter, I have known -16°C . . .
I think, that original poster does not expect, that it should be possible to grow tropical trees in harsh arctic conditions. In my opinion the original poster is looking for trees from highlands of tropical zones, where frosts can happen and therefore trees can handle mild frosts. Tropical trees that are hardy for severe frosts is pretty much oxymoron. Original poster brought a Chinaberry as a sample. Chinaberry is hardy in USDA zones 7-11.
Severe winters here are -35°C. But I still grow plants, that are hardy starting from the zone 9, and some grow even bananas and palms. "Severe" is very dependant on background. For me -16°C is mild. They say, that the climate is warming. I try to be ready, when there will be positive signs towards this warming.
I think, South Mexico, Guatemala and Himalaya are such regions, that are from tropical or subtropical zone, but have highland areas where local trees can handle some frost. Check this source for Guetemalan tree species, that grow in high altitude areas: The Red List of Trees of Guatemala | Botanic Gardens Conservation International Hardiness of tree species should be verified from some other source though.
Towering tropical peaks and ranges can have frequent frosts same as in temperate region mountain ranges. However a key difference resulting in failures of tropical origin mountain plants during northern hemisphere cultivation attempts is that the southern hemisphere is mostly ocean. So that cold periods in southerly tropical mountains do not come with the same low humidity that Arctic blasts hitting northern planting sites do. Also any time and any where that episodic temperature plunges do not continue long enough to freeze the soil deeply that makes a big difference to plant survival as well.
Therefore I suggested highland regions from the northern hemisphere. I don't know, if moist frost is easier to withstand for tropical trees, than dry frost. For human both moist frost and moist heat are harder to endure than dry frost and dry heat. I suppose, there is no deep freezing of the ground in the zone 8.
The reason why Mexico, particularly eastern Mexico, has such relatively cold-tolerant plants is that it is exposed to cold plunges ('Nortes') from the N American Great Plains. The Himalaya don't get similar cold winds from Siberia, as these are blocked by other mountain ranges, and any cold air from the Tibetan Plateau is warmed by compression as it descends the Himalaya to the tree line. So even though the Himalaya are further north, its plants are less hardy (e.g. Himalayan Pinus wallichiana from 28° to 36°N is killed by -25°C, compared to its Mexican close relative P. ayacahuite from 14° to 21°N and unharmed by -30°C). Same goes for further east in China, they get some continental winter cold, but really severe cold from Siberia is blocked to the north by mountain ranges.
But Himalaya is higher, hence has more area of harsh high mountain climate. I suppose, that Quercus lamellosa (an oak from Himalaya) should survive in the USDA Zone 8. I tried in my garden, some seedlings survived first winter outdoors, but died in the spring because of late frosts.
Good morning, I dont have the knowledge to contribute on this subject, but have been reading all the posts with great interest. This has led me to reading more about high altitude trees and plants. I found this article that might be of interest with the changes in the environment for plants and trees moving further upwards away from the heat. Tropical trees are moving to higher elevations to escape the heat • Earth.com
The Himalaya has deep lingering snowfalls that protect mountain vegetation from direct exposure to cold winds. So that it is typical for hardiness to even USDA 8 in other areas to not start to be found among Himalayan plants until the collection site is quite high in altitude.
If extreme hardiness is expected, then this list could give some idea about hardy highland species: Tree line - Wikipedia
