The focus of Sackville-West's collection was, however, on species roses and old garden varieties. Sackville-West described her love of the old roses, saying that one should "discard the idea that roses must be limited to certain accepted and accustomed colours, and to welcome the less familiar purples and lilacs, and the striped, flaked, mottled variations which recall the old Dutch flower-paintings; to approach them, in fact, with open and unprejudiced eyes, and also with a nose that esteems the true scent of a rose warmed by the sun." She was especially fond of the bourbon roses 'Madame Isaac Péreire' and 'Madame Pierre Oger'. Graham Stuart Thomas, who helped locate rose varieties for Sissinghurst and advised Sackville-West on the design of the Rose Garden, described 'Madame Isaac Péreire' as "ossibly the most powerfully fragrant of all roses", and 'Madame Pierre Oger' as having a "formal perfection unique among roses".