Question about Hardiness level

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How some plants manage to grow in places where Hardiness level is higher etc their hardiness level is 7 and manage to grow in a 9.
 
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Urban heat islands and climate change allow frost- and cold-sensitive plants to now prosper in areas where they once regularly perished.

Also, if a tree is planted at a larger size, it may survive where a smaller plant or seedling would perish.

Another simple possibility is that a quoted hardiness rating is in error. Many plants have not been fully tested for in all climates.

There are also other variables to consider. For example, a plant might do fine in dry cold at -5º C in December, but die from a wet freeze at -5º C in April.
 
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Urban heat islands and climate change allow frost- and cold-sensitive plants to now prosper in areas where they once regularly perished.

Also, if a tree is planted at a larger size, it may survive where a smaller plant or seedling would perish.

Another simple possibility is that a quoted hardiness rating is in error. Many plants have not been fully tested for in all climates.

There are also other variables to consider. For example, a plant might do fine in dry cold at -5º C in December, but die from a wet freeze at -5º C in April.

If a tropical tree is big and it snows for 1 day, is it enough to kill the plant? how long i mean, freeze sensitive plants survive under 5 Celsius temperature (41 degrees Fahrenheit)
 
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Hardiness levels/zones only tell you when the average date of first frost is, nothing about actual temperature lows or durations of cold temperatures.
 
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Hardiness levels/zones only tell you when the average date of first frost is, nothing about actual temperature lows or durations of cold temperatures.
No... the USDA Climate Zones are based on annual lowest temperatures, not the date of the first frost.
All_states_halfzones_title_legend_logos_300dpi-84b664ef664942f1a31eaefc23341edb.jpg

Zones 10B and up don't even get frost.
 
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If a tropical tree is big and it snows for 1 day, is it enough to kill the plant? how long i mean, freeze sensitive plants survive under 5 Celsius temperature (41 degrees Fahrenheit)
Are you curious about Jacaranda mimosifolia growing in Athens? Even though Athens has received snowfall in recent years, online sources state that Athens minimum Winter temperatures have stayed above -5º C (23º C) in recent decades. That is mild enough for Jacaranda mimosifolia to survive, though a particularly young or exposed tree could receive frost damage.
 
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Are you curious about Jacaranda mimosifolia growing in Athens? Even though Athens has received snowfall in recent years, online sources state that Athens minimum Winter temperatures have stayed above -5º C (23º C) in recent decades. That is mild enough for Jacaranda mimosifolia to survive, though a particularly young or exposed tree could receive frost damage.
I am interested for Albizia saman / monkey pod and Pterocarpus indicus
 
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Hardiness zones can be somewhat misleading. I live in zone 9a and it's subtropical. I was watching a Youtube video of a food forest in zone 9a; however, it was in the UK, which is temperate. That makes a very big difference.
 
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Yes, the minimum low temperature is just factor to consider with climate, but it s one that is especially to modify outdoors. That is why the frost hardiness of plants is often the first factor considered for suitability.

A 'subtropical' Zone 9a will have generally warm winters with occasionl frosts and freezs, as recently happened this Winter in Florida. Zone 9a in temperate climates, usually either maritime or mediterranean, will have winters that are cool overall, though only occasionally frosty.

Other important climate factors are average and high temperatures, as well as the overall heat index, as well as precipitation, humidity, and wind.
 

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