Others are extremely tender. Cold-hardiness is not determined by the foliage habit. To avoid risk of losing a cultivar, choose daylilies which others have already grown successfully in your climate. Plants all have a basic complement of chromosomes. Most plants are diploid they have two identical sets of chromosomes in each cell.
Polyploids are plants with more than two sets of chromosomes.
A tetraploid is only one of a whole series of polyploids. Triploids have three sets of chromosomes, tetraploids have four sets of chromosomes, et cetera. Tetraploid Tetraploid daylilies are heralded by some growers as having a number of advantages over diploids. Colors of the flower tend to be more intense. Scapes tend to be sturdier and stronger.