Louis-Joseph-Ghislain Parmentier (August 9, 1782 - April 1, 1847)
[From Journal of a Horticultural Tour through some parts of Flanders, Holland, and the North of France, in the Autumn of 1817, by Patrick Neill, 1823, p. 325-332:] Mr. Parmentier's Gardens....Of the genus paeonia there are no fewer than 23 species and varieties, including P. papaveracea, and both the pale and dark varities of the moutan....
[From Journal d'agriculture, 1829, p. 51] List of main amateur non-commercial rose collectors, but who make exchanges. Netherlands [incl. Belgium]...Parmentier, Mayor, at Enghien
[From The Old Rose Adventurer, by Brent C. Dickerson, p. 133: under the listing for 'Parmentier'] Louis-Joseph-Ghislain Parmentier, rosarian, lived 1782-1847; had a very distinguished collection of roses -- including many bred by himself over 30 years and kept to himself -- in Enghien, Belgium; after his death, at least some of these roses were sold off and distributed by others.
[From Roll Call: The Old Rose Breeder, pp. 389-390:]
Born August 9, 1782; died April 1, 1847.
Active by 1818.
... André-Joseph-Ghislain Parmentier, an important American garden architect, was another brother, as was Joseph-Julien-Ghislain Parmentier, quondam mayor of Enghien and fellow horticulturalist.
The catalog for the sale of Parmentier's roses, which occurred following his death, refers to 855 roses "of the first merit" bred by him, of which 800 had never left his garden... [it's quite possible other people introduced his roses as their own]