Mild white mustard ( Sinapis hirta ) grows wild in North Africa , the Middle East and Mediterranean Europe and has spread farther by long cultivation ; brown or Indian mustard ( B. juncea ) , originally from the foothills of the Himalaya , is grown commercially in the UK , Canada and the US ; black mustard ( B. nigra ) in Argentina , Chile , the US and some European countries . Mild white mustard ( Sinapis hirta ) grows wild in North Africa , the Middle East and Mediterranean Europe , and has spread farther by long cultivation ; brown or Indian mustard ( Brassica juncea ) , originally from the foothills of the Himalaya , is grown commercially in Canada , the UK , Denmark and the US ; black mustard ( Brassica nigra ) is grown in Argentina , Chile , the US and some European countries .