Word for banana blossoms in Chinese
There might has been some misconception here.

Banana blossoms (香蕉花) is a food ingredient, it has nothing to do with the nickname for the American born Chinese- 'banana'(香蕉) (which is white inside, yellow on the outside. Meaning they might look Chinese, but they think and act like white people )

Another nickname for American born Chinese is 'bamboo stick' (竹昇), (which is empty inside, meaning they don't have any Chinese character inside them)    


  "tall skinny Chinese person" or "long skinny Chinese person"


The misconception might have came from your Chinese friend thought 香蕉 = 竹昇, and 竹昇 in other context, can be used metaphorically to describe 'tall skinny person'. 

Example: 

'他像竹昇一般又高又廋' (he is tall and thin like a bamboo stick)

'他七呎高卻只得一百二十磅重, 那不就是活脫脫一條竹昇麼？(He is seven feet tall, but only weight 120 pounds, is that not virtually a bamboo stick?)

The fact is, 香蕉 and 竹昇 might mean the same thing, but they obviously are not the same phrase, and the nickname '竹昇' doesn't contain the metaphorical meaning of 'tall and thin person'