In 1991, W. George Schmid published his landmark book, The Genus Hosta (Timber Press, Inc., ISBN-10: 1604690488 ISBN-13: 978-1604690484) which made a number of changes in the way hostas are categorized. Before that time, there had been quite a bit of confusion and disagreement on the taxonomy of the genus.

Kingdom: Plantae
Class: Angiosperm
Subclass: Monocotyledon
Family: Hostaceae (formerly in Liliaceae)
Genus: Hosta
Species: (see below)

Taxonomists (people who categorize and name living organisms such as plants) can go into dizzying detail in their arguments over what constitutes a species. However, for most of us, a simple definition is that the plant either currently exists in the wild or there is evidence (fossils, herbaria specimens, etc.) that it once did.

In his investigations, Schmid found such evidence for 43 species of hostas including the following:

In nature, variations occur within plant species that are not great enough to warrant naming an entire new species. These identifiable variations on the wild species are called varieties. Yes, this term is commonly also used, although incorrectly, to signify what is really a cultivar i.e. cultivated variety.

Identified botanical varieties and forms of hostas include:

When Schmid finally completed his examination of the genus, Hosta, he came to the conclusion that several types which had traditionally been called species were, in fact, cultivated varieties i.e. cultivars. Perhaps the key reason for making this determination was the lack of evidence that these types ever occurred in nature. Rather, they were "created" in the nursery or by plant hybridizers long forgotten.

Plants that Schmid switched from species or botanical varieties to cultivar status included: