This cultivar is listed as diploid in the paper 'Pollen diameter and guard cell length as predictors of ploidy in diverse rose cultivars, species, and breeding lines'

Vance Whitaker wrote roses he used as parents
had different abilities to transmit this
broad based resistance to their
seedlings. ‘Lena’, ‘Pink Gnome’,
‘Prairie Princess’, and ‘Folksinger’
were some of the best for being able to
transmit this type of resistance of black spot