I've had two experiences with this. My friend, who I got my seeds from last year had 2 or 3 vines climbing to the top of a lychee tree were not hand pollinated and produced prodigiously. Then mine, which are sprawled across a long fence, don't seem to produce well without hand pollination. Go figure. It may be that his were close together at the top of a tree lending easier pollination by an insect and mine are far apart. Nevertheless it will produce better and bigger with hand pollination.