Male papaya tree can’t produce fruits, but you need male flowers’ pollens to pollinate female tree’s flowers which then produce fruits.
However, hermaphrodite (雌雄同体) papaya tree is bi-sexual, ie it has male and female flowers, hence it can self-pollinate.
Male papaya tree is useless if you have already a hermaphrodite tree in the garden. You can chop the male papaya tree away. However, there is a mysterious technique to change the sex of a male papayee tree :
Stigma: column cap 柱头
To dwarf (矮化) a papaya tree, trim off the terminal bud.
How to make Thai Green Papaya Salad: