Hostas: Emperors of the Shade

A frequently encountered problem by many gardeners is what to do with a shady area. Light is life to a plant and it seems a bit paradoxical that something that relies on light for its livelihood could thrive with little of it. Hostas represent one good answer to the above dilemma in that they thrive in the shade; additionally, they are low-maintenance, hardy perennials that are easy to grow. Available with impressive leaves that come in a variety of sizes, shapes, colors and variegation, it is little wonder why hostas are sometimes referred to as "emperors of the shade."

Hosta (singular) is the common name given to any number of species, inter-specific hybrids and cultivars belonging to the genus Hosta. Hostas are native to the Orient, where they were discovered growing in the wild in Japan, China and Korea as early as the eighth century. Hostas traveled to Europe by the late 18th century because of European settlements in China. Hosta plantaginea is thought to be the first member of the genus brought to Europe, with Hosta ventricosa arriving soon thereafter. Hostas were classified for years in the genus Hemerocallis (along with daylily), but plant taxonomists ultimately realized hosta was distinct and should be put into a genus of its own. In 1812 the name Hosta was given to this plant’s new genus in honor of Australian botanist Nicolas Thomas Host. Unfortunately, this name had been given to a genus in the family Verbenaceae and, according to the rules of naming plants, the same name cannot be given to two different plants. The error was corrected in 1817 when the name Funkia was given to hosta. This designation prevailed until 1905 when the governing body for plant nomenclature changed it back to Hosta. One hundred years later, it is not uncommon to see the term Funkia parenthetically inserted behind Hosta in magazines and catalogs.

It is estimated there are 70 species and more than 4000 cultivars of hostas available today. They range in size from miniatures (e.g., ‘Baby Bunting’ and ‘Tiny Tears’) which are only several inches in diameter at maturity to giants such as ‘Sum and Substance’ and ‘Blue Angel’, which approach a height and spread of 48 inches. Within those extremes, hostas usually are placed into one of five different categories according to height or leaf color. These include dwarf, edger, groundcover, background and specimen. The latter category applies to hostas of any height with colorful or unique leaves. Leaf color varies among solid colors of green, blue and yellow or variegated in any number of combination of these colors. Most of the variegated cultivars have dark leaves with light or colored edges. A few cultivars are viridiscent, meaning they change from light in color to darker shades during the growing season. Others are lutescent and change from green to yellow during the growing season. A very few change from yellow to white, a trait know as albescence. Additionally, hostas can be classified according to their leaf shape (strap, lance, egg, heart and circular) and leaf surface (flat, rugose, cupped-rugose, wavy undulate, contorted, piecrust or furrowed).

Like daylilies, hostas bear a compound in florescence known as a scape. Individual flowers on the spike are lavender or white, depending upon cultivar. Some flowers (e.g., cultivars of H. plantaginea) are delightfully fragrant, adding yet further appeal to this attractive plant.

Although hostas are considered shade plants, most do not thrive in deep, heavy shade. An ideal scenario for most cultivars is several hours of morning sun followed by afternoon shade, or broken patches of sun/shade that might be characteristic of the exposure under a large, open tree. Hostas have fairly aggressive roots that compete well with the roots of most tree species. As a general rule, the blue-leafed cultivars require a shadier exposure while the green- and yellow-leafed cultivars can tolerate more sun. However, most of the sun-tolerant cultivars will exhibit some leaf-edge burn if exposed to afternoon the afternoon sun and heat characteristic of a Midwest summer day.

Some hosta cultivars require years to develop into a mature clump. Therefore, they represent a long-term installation in the garden and adequate soil preparation is a sound investment. Hostas prefer a rich loam soil high in organic matter that is slightly acidic in nature. Good drainage is also important. Deeply incorporating about four inches of organic matter is a good way to prepare average soil for hostas. Well-rotted manure, compost, leaf mold or peat are good sources of organic matter. Since hostas have fairly deep, aggressive root systems, the hole in which they are to be planted should be about 12 inches deep and 1 and 0.5 times the mature diameter of the cultivar being planted.

Hostas are readily available as dormant divisions, but one can hasten their establishment in the garden by purchasing plants that are already started in nursery containers. Upon planting, remove the hosta from its container and free any tangled roots. Place the plant in the planting hole so that the roots will be covered with soil to the same level they were in the nursery container. If dormant divisions are planted, the roots should be soaked in water for about 30 minutes before planting. In both cases, water thoroughly after planting has been accomplished.

Fertilizing remains a controversial topic among hosta experts. Some insist that growing soils containing sufficient amounts of nutrients do not need additional fertilizer while others maintain supplemental fertilization is beneficial. The latter suggest the addition of a granular, complete fertilizer (e.g., 12-12-12 or 5-10- 5) early in the spring, followed by two additional applications, each approximately six weeks apart. Apply according to label directions and the stature/vigor of the cultivar being fertilized. It is important not to fertilize hostas after the middle part of July to avoid stimulating late-season growth and preventing the plant from hardening for the winter.

Hostas require about 1.5 inches of water per week during the summer. Burned leaf tips are a tell-tale sign of insufficient amounts of moisture as are drooping leaves. If supplemental irrigation is required, then water early in the morning to allow leaves to dry as quickly as possible. Hostas are easily increased by dividing the clump early in the spring when the shoots start to emerge from the soil. Most cultivars, however, should not be disturbed for about five years after planting to allow the clump to be established.

Slugs and snails are especially fond of hostas and the shady, moist environment enjoyed by hostas is favored by these two pests. They typically chew small, round holes in the leaves of plants on which they feed and leave a dried trail of slime as they move from one spot to another. Poison baits containing measurol, metaldehyde or iron phosphate have been shown to be effective in controlling slugs and snails as has been placing pans filled with beer in the garden. The latter is attractive to these pests which will crawl into the pan and drown. Deer also love hostas and represent a more formidable challenge to control. Repellents, electrical fences, guard dogs and motion detectors have all been used to control deer, to greater or lesser effectiveness.

Other than foliar nematodes, hostas are relatively disease free. Hosta Virus X (HVX) is a new virus that has been getting a lot of publicity as of late. On cultivars with light-colored leaves (e.g., Gold Standard) symptoms include blue or green markings. These markings usually follow the vein of the leaf out into the surrounding tissue, resulting a mottled appearance. A lumpy or puckered appearance to the leaf may also be present. Symptoms on cultivars with dark-colored leaves are more difficult to detect and may appear as light-colored mottling instead of colored streaks. HVX is spread by mechanically transferring it from an infected plant to a healthy one, especially during propagation. There is no cure for this disease and gardeners should rogue out any suspect plants from their collection.

As mentioned above, there are over 4000 hosta cultivars from which to choose. The American Hosta Society polls its membership each year to determine their favorites. For the entire list go to: www.hosta.org/Major_Awards/ahs_popularity_poll.htm on the web.

Other excellent, attractive cultivars exist that do not appear on the popularity poll. When in doubt, look for a cultivar that has won an award given by the American Hosta Society such as the Eunice Fisher Award or the American Hosta Growers’ Hosta of the Year Award. Once considered a green filler for shady areas, hostas are now the stars of shady landscapes because of the plethora of cultivars available to today’s gardening public. Plant some this fall if you are not already enjoying this easy-to-grow perennial.

David Trinklein
Horticulture
573-882-9631