There are 50-70 species of Hosta, and at least 40 of them are found in cultivation. And, there are more than a thousand named cultivars and hybrids! Some of the cultivars were selected many years ago from wild species that didn't yet have botanical names, and the origins of many others have simply been forgotten. Some of the hybrids have many different species (and long-lost cousins) in their pedigrees. For many of the cultivars and hybrids it is not even possible to assign botanical names. Most gardeners don't even try; they just use the cultivar names. Fortunately, horticultural uses and cultivation requirements are similar for most hosta species and cultivars.
Hostas are grown mainly for their attractive, often striking, foliage that grows in mounds of overlapping leaves, all of which originate from a single basal tuft. Some hostas are no more than 6 in (15 0cm) tall and some get up to 3 ft (0.9 m) tall with a similar spread. Leaves range from elliptic to heart-shaped, and vary among cultivars from tiny miniatures about an inch across to "elephant ear" types more than 2 ft (0.6 m) long. Leaves can be smooth or puckered, even twisted, and can be green, yellow, gray, or bluish, with various kinds of cream or yellow variegations. Like other lilies, the leaves have distinctive parallel veins. In summer, lily-like flowers are held on slender stalks that stand above the foliage, and their colors range from blue to lilac to violet to green to white. Some hostas produce very showy floral displays and some are fragrant. However, many gardeners remove flower stalks as they appear in order to encourage the foliage. In autumn the leaves turn yellow before wilting completely for their winter rest period. Hostas have fleshy roots and short rhizomes (underground stems) by which they spread to form larger clumps. There are more than 1000 named cultivars registered with the International Society for Horticultural Sciences.
Most of the wild species of Hosta grow in Korea, China and Japan. Hostas have been cultivated, hybridized and selected in Japan for centuries, and more recently European and American fanciers have gotten into the act.
Hostas are easy to cultivate in fertile, moist soil with a pH near neutrality. If you aren't interested in the flowers, or if your hosta is less than a couple years old, you might want to cut the flower stalks off so the plant can devote more energy to foliage development. The very young leaves of hostas are prized by snails and slugs, and the older leaves are sought out by gourmet deer.
Light: Hostas do best in shade or partial shade. They like some morning sun, but never plant hostas where they will be subjected to afternoon sun. In the north, hostas do best with full sun in the morning. The green and gold-leaved types may be able to tolerate a little more sun than those with gray or bluish leaves. Moisture: Hostas produce the best foliage with regular water during their growing season, but they can tolerate drought if they have to. Mulch in summer to retain soil moisture. Hardiness: USDA Zones 3 - 9. Not all varieties are hardy to zone 3. Hostas need a rest period with temperatures below 40ºF, (4.4 ºC) with most varieties needing about eight weeks, although some can get by with less. Most hostas do not do well in the deep south, but there are a few varieties that can be grown in northern Florida where I live. Alternate freezing and thawing in the root zone may be fatal to some varities. Propagation: Hostas are propagated by dividing the root clumps. In early spring, just as the plant's little "bullets" are beginning to emerge from the ground, you should be able to identify the individual crowns that have developed around the original. Use a sharp spade to separate one or more out from the rest. Hostas should not be divided more often than every 3-5 years. Commercial producers propagate hostas by the millions by culturing a few cells in glass test tubes.
Hosta 'Big Boy'
Hostas are a mainstay in shady gardens. They thrive where the grass won't grow. Hostas do so well and are so easy to divide, that they can be used as ground covers under trees and shrubs. In autumn, the yellowing leaves last long enough to be worthwhile fall color, and the persistent flower stalks and seed heads of some types are a strange and ghostly sight in winter. A clump of large-leaved hostas looks great at the base of a large tree or stump. Use hostas in shady herbaceous borders and in woodland gardens. They often are used in the background behind more sun-loving plants. Line a shady path with medium size hostas. The smaller types are effective in rock gardens, as edging and in containers. Cut leaves are prized in floral arrangements.
Gardeners in Japan have been cultivating hostas for centuries, but these shade-loving perennials have become popular with westerners only in the last few decades. Now there are hundreds of hosta societies; the American Hosta Society is one of the largest, and the Hosta Network lists some smaller, local hosta societies.