Analysis of information sources in references of the Wikipedia article "אתרוג בלאדי" in Hebrew language version.
Citrus plants are no natives of Palestine.
From there it reached Babylonia, where it came to the notice of the exiled Jews, who later brought it back to Israël.
{{cite book}}: (עזרה)Of the fruits now grown in Palestine, it is believed that the citron (Ethrog in Hebrew) is the oldest known in that country.
Etrogim were, of course grown from ancient times in Palestine and individual citron reached European Jewish dignitaries, but there was no significant trade until the latter part of the nineteenth century.
The fruits were cultivated in Palestine and exported to Jewish communities settled in Europe.