Book  (1928)  Page(s) 102.  
 
Descriptive List of Chinese Peonies
H. A. Hagen. (Richardson, 1904.) 8.2.
Double type; large; late. Dark rose-pink throughout; a very compact, globular flower, with overlapping petals, evenly graduated from the outside to a small, perfect, rose center; the tips of the petals reflex in the middle of the flower, giving a peculiar shadowy effect, and the outer petals relax with age but keep their incurved cup form; excellent fragrance. Medium height; fairly vigorous and floriferous; stout stems. Short, broad foliage.
An excellent dark pink peony, particularly deserving because of its fine form and pure, even color. Described by some as uniform violet-rose.
"Somewhat similar to E. G. Hill but much superior."—Thurlow.
"Rating too low. This is really a very superior variety and should carry a rating of 9.0."—Fewkes.

Website/Catalog  (1920)  Page(s) 31.  
 
Brand's List of Selected Peonies
Pink and Rose Varieties
H. A. Hagen. Not for sale.

Website/Catalog  (1920)  Page(s) 16.  
 
Double Flowering Peonies
H. A. Hagan. (Richardson.) Large, compact, rose type. Uniform, deep violet-rose. Fragrance X. Late....$5.00

Website/Catalog  (1918)  Page(s) 14.  
 
Paeonia albiflora: Richardson Seedlings.
The following Peonies are seedlings raised by the late Mr. John Richardson of Dorchester, Mass., who was well known as a very skillful horticulturalist. The Peonies that he originated include some of the finest known varieties.
H. A. Hagen. Bright clear pink, uniform color throughout, perfectly double. Very erect and a beautiful color, very free blooming, mid-season. Choice. $4.00.

Book  (1907)  Page(s) 102.  
 
1090. HAGEN, H. A.; P. albiflora...(Richardson and Jackson)
(1) 1904, Trans. Mass. Hort. Soc., part 1, p. 181.

Magazine  (1904)  Page(s) 181.  
 
"John Richardson: His House and Garden." By Robert Tracy Jackson, Cambridge, Mass.
Presented for publication, October, 1904.
Description of Mr. Richardson's Seedling Peonies.
The following is a list with descriptions of the Richardson seedling peonies, with synonyms where such exist and the awards they have received; these awards were all made by the Massachusetts Horticultural Society, so that for the sake of brevity the name of the Society is not further mentioned. The date of blooming this year is given, and also the height. The height was taken in August, and measures the distance from the ground to the calyx of the flower; with the flower, therefore, some inches would be added as a maximum height. The whole set of eighteen varieties was exhibited this year before the Society either on June 5, 11, or 21-22.
H. A. Hagen. Named by me. Bright, clear pink, cupped, exquisite color, perfectly double, no stamens or stigmas visible, all petals of a uniform color, flowers stand up very erect on the plant, quite close to "Norfolk"; but more uniform in color throughout. Posthumous seedling of Mr. Richardson's. In bloom 17 June 1904, height to flower 32½ inches. Named for the late Dr. H. A. Hagen, entomologist.