@ShawnSteve
Missouri Botanical Gardens: Leucanthemum x superbum, commonly called Shasta daisy, is a hybrid developed by Luther Burbank (1849-1926) in the 1890s near snow covered Mt. Shasta in northern California. Burbank crossed Leucanthemum vulgare (European oxeye daisy), Leucanthemum maximum (Pyrenees chrysanthemum), Leucanthemum lacustre (Portuguese field daisy) and Nipponanthemum nipponicum (Japanese field daisy) to produce Leucanthemum x superbum which was given the common name of Shasta daisy.
Leucanthemums were formerly included in the genus Chrysanthemum.
Also from Missouri Botanical Gardens: Nipponanthemum nipponicum, commonly called Nippon daisy, is a shrubby perennial which grows 1.5-3' tall. Features 2-3" diameter flower heads with white rays and green center disks. Flowers appear in fall on long stalks. Thick, oblong, coarsely-toothed, glossy, dark green leaves (to 3.5" long). Excellent and long-lasting fresh cut flower. Formerly known as Chrysanthemum nipponicum.
As far as Garden Mums, there is no specific definition as to how old it has to be to qualify.
