I'm sure many garden-book authors have neatly divided and precisely labelled all types and styles of gardens, but how porous and intermingled those categories truly are.
Yes, on average, Medieval peasants and Romantic poets probably did garden the plot of land around their 'cottagey' hovels somewhat differently, but flowers would have still been everywhere, even on crop plants. Also, why should we coarsely assume that even the most frugal and industrious bucolic would not have cultivated some plants for sheer ornament and beauty. Conversely, the aforementioned romantics would still have had to descend occasionally and eat physical food from a potagerie. For that matter, poppy flowers were probably more a source of opium than beauty, for the more extreme decadents.