Alessandra these are tropical plants (Carica papaya) and would be unlikely to fruit in a mediterranean climate. They grow well in subtropical zones as well. I grew up in a substropical area of South Africa and we used to cover the green fruit with plastic bags till they were ripe so the monkeys couldn't eat them. We also put rubber snakes in the trees to deter them! There are paw paw trees growing here in Adelaide (mediterranean) in the botanic gardens, but they don't fruit. I think the summer is too short - this is my experience with guavas here. The fruit forms but never ripens. Liz