I seem to have made a mistake. I thought apple trees could cross pollinate as long as there was a different variety so I planted a yellow transparent apple tree and then a white transparent apple tree. Do I really need to plant a third different kind of apple tree for cross pollination to happen? I didn't know that "white transparent" was the European term (I bought this tree from B&Q) and "yellow transparent" was the American term (I bought this tree from Costco).