Reading Harry Potter and thoughts turn to gardening

Purslane - is this what Gillyweed might look like?

I am reading all of the Harry Potter books this summer and my thoughts turned to gardening, as they always do.

Naturally, I am interested in the references to herbology as one of the subjects that the young wizards and witches study. 

I noted today that it was mentioned in the fourth book that none other than Neville Longbottom seemed to do