They are called "evergreen" plants but the leaves do fall down and get replaced, just not all at once.
Leaves fall down due to the force of gravity pulling on them.
Bougainvillea plant fall their leaves during a hot day.
evergreen
simply when they droop and get attracted by gravity.
In the fall when the plant stops making chlorophyll.
No cut them off
The leaves fall down.
the katydid will never survive in the fall.
An important fact about plant pigments is that it colors the plant green. It also makes leaves yellow and orange in the fall.
They fall off and turn rainbow colors )
The orange and yellow are in the plant,but are invisible because the plant has to much chlorophyll.In the winter,the chlororphyll does not have good weather and it breaks down and vanishes to only see the yellow and orange.
Things fall down b/c gravity pulls in that direction. Fruits and leaves fall down when the added force of being shaken together with gravity becomes bigger than the strength of the attachment to the tree.