Article (magazine)  (Jan 1955)  Page(s) 13.  
 
There were also hundreds of lilac pinks, magenta. pinks and plain magentas, most of which were very unattractive. Many closely resembled Banksi. Typical varieties were 'Archduc Ludovico,' 'Athlete,' 'Beaute de Twickel,' 'Jules PirIot,' 'La Ville de St. Denis,' 'Morris,' 'Princess Louise,' 'Reine Amelie,' 'Reine des Fleurs,' 'Triomphe de Vandermaelen,' and 'van Houttei.' All these varieties proved, in Holland and France, easy to propagate in comparison with the later introduced Japanese varieties. Which varieties bearing European names were actually raised from seed in Europe and which were Chinese varieties renamed is not too definitely established.

Magazine  (Sep 1944)  Page(s) 50.  
 
Tree Peony Supplement to the Manual
John C. Wister, Germantown, Pa.
Alphabetical Check List of Tree Peony Names, August 1944
Chinese (or sometimes called European) Moutan type; Lilac Rose; TRIOMPHE DE VANDERMAELEN (Vandermaelen, 1849) (Syn. Triomphe de Flandres)
V. Lemoine Nursery, Nancy, France, 1887; Louis Van Houtte, Ghent, Belgium, 1873; Auguste Dessert, Peony specialist, Chenonceaux, France, 1889; E. H. Krelage Bulb grower and Nursery, Haarlem, Holland, 1867; Louis Paillet, Chatenay (Seine), France, 1880; Old Farm Nursery, Boskoop, Holland, 1924; Bobbink & Atkins Nursery, Rutherford, N.J., 1940; Oberlin, 1941; Cottage Gardens Nursery, N. I. W. Kriek, Lansing, Michigan, 1941-2 (last catalogue printed 1942 and still in use).
Name in Large Caps in Black Type indicates accepted names of varieties in American commerce 1944.

Website/Catalog  (1940)  Page(s) 6.  
 
European Tree Peonies
48. Triomphe de Flandres. Large; double; salmon pink...$6.00

Website/Catalog  (1940)  Page(s) 6.  
 
European Tree Peonies
49. Triomphe de Vandermaelen. Large; double; vivid violet-pink. Vigorous grower...$5.00

Website/Catalog  (1931)  Page(s) 6.  
 
Tree Peony
Triomphe de Vandermaelen. Enormous flowers with vivid violaceous pink petals.

Website/Catalog  (1924)  Page(s) 152.  
 
Pivoines en arbre...Triomphe de Van der Maelen.- Grande, pleine, rose violacé vif.

Book  (1907)  Page(s) 85.  
 
876. FLANDRES, TRIOMPHE DE; P. moutan.
(1) 1906, Dessert's Cat. p. 43.

Website/Catalog  (1906)  Page(s) 37.  
 
Paeonia arborea. Tree-Peonies. A selection of especially fine double sorts.
Van der Maelen, light violet, centre cherry-red, densely filled.

Book  (1898)  Page(s) 108.  
 
La Pivoine en arbre a fourni à la culture un grand nombre de variétés horticoles, les unes obtenues en Chine, et d'autres en Europe...Quant aux variétés horticoles, elles sont si nombreuses que nous ne pouvons citer que les plus remarquables.
Principales Variétés Horticoles
[Triomphe de] Van der Maëlen Van der Maëlen.—Très pleine, violet clair.

Website/Catalog  (1893)  Page(s) 42.  
 
Tree Pæonies.  Pæonia Arborea.
This beautiful group of shrubs is among the oldest of introductions from Japan, but magnificent new varieties have been added from year to year until we have a long list of wonderful forms.  They are quite distinct from the herbaceous section, and have shades of color not found in the latter; and when once established form compact bushes, which in spring are covered with the gigantic blooms.  These pæonies are a little tender in exposed situations north of Boston; but if planted in a sheltered, warm location, and protected during the first two winters by a covering of pine boughs, or other loose material, will eventually establish themselves, and form one of the most decorative features of the garden.  Like the herbaceous kinds, they enjoy rich soil, and the blooms last longer and come finer when partially sheltered from the hot sun.  They are well worth the little trouble entailed in their cultivation.  We can offer strong plants of the leading and most hardy kinds; but as they are slow and difficult of propagation, this fact will account for their relatively higher cost over the herbaceous kinds.  Having secured a large stock of these beautiful plants, we are enabled to offer them at lower prices than ever before.  2 year plants, 75 cents each; 3 year plants, $1.00 each.
Triomphe de Vandermalaen.  Enormous flower, incurved, perfectly formed, purplish rose; centre darker shade.