I don't know if my location is very relevant ...
As i said in the beginning, i bought a kumquat in a pot from the supermarket.
It most probably came from Italy ...
I placed it in a larger pot where i added some
local soil plus some store bought one.
After some time i sensed some wonderful fragrance from this pot and i thought the kumquat had flowered ...
But no, it was this suspect.
Now, i use this same soil mix to repot hundreds of other plants and no perfumed flowers arose till now so i think this "clover" came from the original pot.
That means most probably it came from the mediterranean area which made me suspect trifolium alexandrinum.