Our hardy Hibiscus species as ornamentals
As a common plant name, "Hibiscus" is more often applied to the showy tropical sorts, especially Hibiscus rosa-sinensis L., than to other species of the genus. There is, however, another equally showy group, the hardy herbaceous mallows, native mostly to the Eastern United States. This group includes Hibiscus moscheutos L., H. militaris Cav., H. coccineus (Medicus) Walter, H. grandiflorus Michx., H. lasiocarpus Cav., and their many garden hybrids. The various species in this group are commonly called Rose Mallows. They grow naturally in marshy areas of the Atlantic States from southern New England to Florida, also inland along rivers and lakes. Isolated populations appear in areas such as the Sacramento River Valley of California. The tall vigorous growth of Rose Mallow plants plus the abundantly produced, large, gaily colored flowers makes them a conspicuous and attractive feature of the vegetation. Hibiscus moscheutos most often occurs in almost pure stands along tidal rivers of the mid-Atlantic states. During the peak of flowering, late July to mid-August, these stands are a striking sight to behold. In spite of the large fleshy roots, Rose Mallow plants withstand transplanting easily even when in full flower. They are also readily groxvn from seed and will flower the first season if sown early. Unlike their woody tropical relatives, the Rose Mallows are herbaceous perennials, and the plants become somewhat coarse by the end of the growing season. They also lack the yellow and orange flower colors so prominent in many Hibiscus rosa-sinensis clones. Nevertheless, the various species have been cultivated as ornamentals in the United States since Colonial times. As cultivated plants they perform best when grown in good garden soil with moderate amounts of water.
Genetic affinities of the North American species of Hibiscus sect. Trionum
Study of herbarium specimens, crossing behavior, chromosome conjugation, and live populations has shown that the endemic North American species ofHibiscus sect.Trionum comprise two distinct genetic groups.Hibiscus militaris Cav. andH. coccineus Walt, crossed readily and yielded fertile Fi’s. Also,H. incanus Wendl.,H. moscheutos L., andH. lasiocarpos Cav. crossed freelyinter se, and the hybrids were all vigorous and fertile. However, crosses of these three forms with eitherH. militaris orH. coccineus gave lethal hybrids. Preliminary evidence suggests thatH. palustris L. is similar toH. moscheutos, H. incanus, andH. lasiocarpos in crossing behavior. These four forms were found to occur in distinct geographical areas. They may be considered as ecotypes of a single ecospecies.H. grandiflorus Michx. is morphologically related to this alliance, but yielded a viable fertile hybrid when crossed withH. coccineus. Further study of the affinities ofH. grandiflorus andH. palustris is in progress.
Studies on the Specie and genus crosses in Malvaceae (I) : The F1 hybrid, Hibiscus mutabilis, L. x H. Moscheutos, L.
1. The reciprocal crosses were madc between H. mutabilis and H. Moscheutos as the studies on the hybridization in species and genus crosses in Malvaceae and F1 seeds and plants Were obtained from H. mutabilisxH. Moscheutos. 2. The set % of pods in H. mutabilis X H. Moscheutos was 35. 26%, but that of pods having the viable seeds was 13. 16%, and the pod fertility, percentage of pods having the viable seeds per total pods, was 37. 31%The size of pods obtained in H, mutabilis X H. Moscheutos was smaller than that of the selfed mother, the shape of F1 seeds obtained resembled the mother plant, but its size was smaller. which was shrub. 3. The number of the viablc seeds per pod obtained in H. Mutabilis X H. Moscheutos was only 3. 3, but that in pods having the viable seeds was 8.8. The germination % of F1 sceds was 41.67%, showing the lower value than those of the parents. 4. The shape of cotyledons of F1 quite resembled the father plant, but its size was smaller. The shape of leaves of F1 was rather similar to the mother plant rcsembling the intermediate shape bctween the parcnts. The shape of flowers of F1 quite reselmbled the father plant, but its size was smaller, showing the. intenrrediate size of the plants. The colour of flowers of F1 was dark pink, but that of the mother plant was white, and of the father plant was light pink. The time of blooming of F1 in the first year of growth was later than the intermediate time of the parents, but that in the second year of growth was equal to the mothel plant, bloonrling earlier than the father plant. 5. In F1 the plant height was low showing the similarity to the mother plant at the early stage in the first ycar of growth, but elongated to the height of the father plant in the middle of October, and became at the end taller than those of the parents in the middle of October in the second year of growth. The thickness of stems of F1 was more than those of thc parents, and the numbers of leaves, nodes and branches were more nurnerous than thowe of the parents. The plant type of F1 was variou observing 9 types, and no individuals of the same type to the parents were obtained. The tissue of stems of F1 quite resembled to the mother plant which was shrub. 6. The pollen grains of F1 were of various sizes and almost all the pollcn grains were abortive, and the pelcentage of good pollen grains was O. 3%. Thet size of good pollen grains of F1 was larger than those of the parents. The number of pollen grainsper anther of F1 was more numcrous than those of the parents.