Planting the trees
(How many rows can you make?)

     A farmer bought 21 peach trees from the nursery and wants to plant them in rows of 6 trees each. Because 6 is his lucky number he wants as many rows of 6 as he can make. The more 6 row trees the more times his lucky number is applied. What is the maximum number of rows he will be to plant, making sure there are 6 trees in every row?    (hint: it is more than 3 rows)