Burning bush

Most everyone is familiar with the story where Moses comes across a burning bush which, while clearly alit, doesn’t seem to be consumed by the flame.  

It’s supernatural. 

Except, it’s real — well, part of it.  

There’s a bush called  Dictamnus albus, a flowering plant native to parts of Europe and Asia  (but not North Africa or the Middle East, and it doesn’t come with the  voice of a higher being).   
For most of the year it acts as a normal  plant, but over the summer months, it develops a sticky, flammable oily  substance which sometimes spontaneously sparks in the heat.  
The  excretion, when lit, burns rapidly — so rapidly, in fact, that the plant  itself is typically unscathed.
 
The oil’s smell is citrus-like, but the plant’s leaves are bitter  and inedible.  (Why one would want to eat a flammable plant is anyone’s  guess — well, anyone other than Homer Simpson.)  
It has some archaic medical uses but today is mostly cultivated for its novelty factor — in case you wanted to grow one yourself.