In my first of a four-part series on the Korean hostas, I covered H. yingeri, and H. laevigata. In staying with the theme of southern island species, this article will examine the similar species, H. tsushimensis and H. jonesii. We will look at the characteristics of the species, how they have been used in hybridization programs, and their potential for breeding hostas in the future. Use these discussions to take a closer look at these hosta species and perhaps use them in your breeding programs to isolate their desired characteristics.
Hosta tsushimensis
Hosta tsushimensis is only found on Tsushima Island, which is in the Korean Strait between the Korean peninsula and Kyushu Island in Japan. There it is found on both moist and dry sites. The morphology (appearance and structure) of the plant is similar to the Japanese species H. tardiva and H. tibae, from which it is thought to have originated. Typically about 12 inches (30 cm) tall and 30 inches (76 cm) wide, other characteristics can vary significantly in wild populations. The leaf margins may be smooth or undulating with fine serrations. The overall shape of the leaves ranges from narrow-lanceolate to widely-oval, even heart-shaped. The color is light green on the upper surface and a glossy lighter green below. The arrangement of flowers on the scapes (inflorescences) are branched in some populations, unbranched in others. Flower scapes reaches 24 to 30 inches (61 to 76 cm), and produces an abundance of two-inch funnel-shaped flowers, for which the species is valued. Though normally found with light purple flowers, a white-flowered form exists, ‘Albiflora’ (also known as ‘Shirobana Tsushima’). Two sports exist with darker veins on a lighter green leaf background. They are ‘P.M. Stripe’ and ‘Busen Sugita.’ A rare yellow-flowered form, obtained by Mark Zilis from friends in Japan, is now marketed under the name ‘Miracle Lemony.’
A cultivar of H. tsushimensis with yellow leaves is ‘Ogon Tsushima’. Bob Solberg is one breeder that has used this plant extensively in his hybridization programs. Bob crossed ‘Ogon Tsushima’ with H. yingeri, and obtained the yellow foliaged cultivars ‘Whiskey Sour’ and ‘Sun Catcher’. H. ‘Whiskey Sour’ was crossed with an unnamed sibling to obtain ‘Strawberry Banana Smoothie.’ This was then crossed with an F2 seedling of H. clausa var. normalis. The resulting plant, ‘Beet Salad’, has red petioles and is a good breeding plant for this highly desirable characteristic.
Hosta jonesii
Taxonomically similar to Hosta tsushimensis is H. jonesii. M. G. Chung (1) discovered it in the late 1980’s and named it after the plant explorer, Dr. Samuel B. Jones, professor emeritus, University of Georgia. The Korean name for the species translates to “several islands.” It is found on several islands off the southern coast of Korea, primarily Dolsan, Jin, Namhae, and Oenaro. Habitat of the species is dense, dry shade. H. jonesii differs from H. tsushimensis in three primary ways: It has a creeping rhizome, reddish-purple dots at the base of the flower scapes, and flowers that are larger and somewhat bell-shaped. Like H. tsushimensis, the morphology is similar to H. tibae. H. jonesii may be closely related to H. tibae, though this relationship has not been analyzed using genetic or biochemical studies. All three of the species have branching scapes. W. George Schmid (2) reports that Samuel B. Jones noted the branching of the scapes eventually disappeared in H. jonesii. Average size of H. jonesii is about 8 inches tall by 18 inches wide (20 cm x 45 cm). Its growth rate is more vigorous than H. tsushimensis. The leaves are smooth and dull green on the upper surface and a glossy lighter green below. Scapes are erect to a height of about 12 to 24 inches. The nearly purple flowers have white veins on the inside, again similar to H. tsushimensis.
George Schmid (3) states that H. jonesii is a worthy plant but as of now, cultivars or selections are rare. Dr. Jones never shared H. jonesii. The species never left his garden.(2) Don’t be in such a hurry to run out and buy a breeding plant. Because H. jonesii looks similar to H. tsushimensis and H. tibae, U.S. distributors are not always able to detect the differences and inadvertently sell a plant as H. jonesii when it is not.
Knowing the characteristics of hosta species and isolating those traits in breeding programs may result in unique plants for the hosta market. Bob Solberg states that he never intended to just use the Korean species for producing red in the petioles, but the similarity of the genes of the Korean species may have helped push the red color further into the leaves. This characteristic, as well as the compact size, the abundance of flowers on branched scapes, the rhizomatous habit of H. jonesii, and the tolerance to a wide range of growing conditions, make H. tsushimensis and H. jonesii worthy plants in any garden or breeding program.
References:
- Chung, M.G., Jones, S.B., Hamrick, J.L., and Chung, H.G. “Morphometric and Isozyme Analysis of the Genus Hosta (Liliaceae) in Korea.” Plant Species Biology, 6 : 55-69. 1991.
- Schmid, W. George. Correspondence
- Schmid, W. George. The Genus Hosta – Giboshi Zoku. Timber Press, Portland, OR. Batsford Ltd. London. P. 64-65, 316. 1991.
Upper left: Hosta tsushimensis, Upper right: Hosta jonesii, Lower: ‘Beet Salad’ showing red petioles on right.
The Cottage Gardener 