" And how do trees register that the warmer days are because of spring and not late summer? The appropriate reaction is triggered by a combination of day length and temperature. Rising temperatures mean it's spring. Falling temperatures mean it's fall. Trees are aware of that as well. And that's why species such as oaks or beeches, which are native to the Northern Hemisphere, adapt to reversed cycles in the Southern Hemisphere if they are exported to New Zealand and planted there. And what this proves as well, by the way, is that trees must have a memory. How else could they inwardly compare day lengths or count warm days? "

― Peter Wohlleben