Grubby plant never cook so good appears to be a phrase or statement that does not have a widely recognized meaning or context. It is possible that it is a creative or poetic expression that plays with language and imagery. Interpreting it metaphorically, one could imagine it referring to a humble or seemingly insignificant plant that, despite its appearance, produces unexpectedly delicious or satisfying results when used in cooking. This could represent the idea that appearances can be deceiving, and sometimes the most unassuming things can bring joy or success. However, without further context or information, it is challenging to provide a more precise interpretation or explanation. If you can provide additional details or context about the phrase, I would be happy to offer a more tailored response.