The meaning of 'grow thhrough a mass of tightly packed leaf covers'

I cannot get the meaning of "which grow slowly through a mass of tightly packed leaf covers." in the below paragraph.


I know this kind of explanation is not easy. But who knows if there is anyone who give me the exact picture of that tricky sentence.


Thanks.


The banana tree is the largest plant on earth without a woody stem. The trunk contains a large amount of water and is extremely delicate. Though it can reach a full height of 20 feet in one year, even moderate winds can blow it down. The fruit stem or bunch is made up of seven to nine hands, each containing 10 to 20 fingers which grow slowly through a mass of tightly packed leaf covers. Just before they ripen, they are picked, packaged, and finally delivered to our local supermarkets.