About Hibiscus calyphyllus Cav.
Hibiscus calyphyllus Cav., common name lemonyellow rosemallow, is a shrub in the genus Hibiscus native to tropical Africa. This species has a history of taxonomic confusion under several different scientific synonyms: Hibiscus calycinus, Hibiscus chrysantha, Hibiscus chrysanthus, and Hibiscus rockii. In 1883, this plant was sold in England under the name Hibiscus chrysanthus, with its source recorded as Port Natal, Cape Colony, which is now part of South Africa. By 1891, the same plant was sold under the name Hibiscus chrysantha in the United States, and this naming practice continued into the 1930s, contributing to incorrect species identification. In 1892, the name Hibiscus calycinus was established as the correct name for the species. By 1894, the currently accepted scientific name, Hibiscus calyphyllus, began to be used in association with Hibiscus calycinus. At the start of the 20th century, this species was sold as seed in the United States under the common name Hibiscus Giant Yellow. Due to their similar flowers, Abelmoschus manihot was very often confused with Hibiscus calyphyllus in early 20th century United States gardening literature, especially when discussing cold tolerance. If the species identification in the 1903 report published in The Flower Garden is correct, the report states: "Giant Yellow is a beautiful canary yellow with crimson throat, hardy as far north as St. Louis, but safer in the cellar above that latitude". This suggests Hibiscus calyphyllus may have some level of cold tolerance. St. Louis, Missouri is located in USDA Zone 6a, but there are no current reports of Hibiscus calyphyllus successfully overwintering in Zone 6a. It is confirmed to overwinter successfully in USDA Zone 8a. Hibiscus calyphyllus grows to between 1 and 1.8 meters (3.3 to 5.9 ft) tall. It produces flowers that reach 8 to 10 cm (3.1 to 3.9 in) wide; the flowers are yellow with a brownish center. Unlike many African Hibiscus species, which bloom from fall to late fall, Hibiscus calyphyllus blooms in summer. This summer blooming habit means it can be grown in many locations across North America and Europe, and produces viable seeds that are easy to collect and germinate. If seeds are started indoors early in February or March, Hibiscus calyphyllus will bloom in its first growing year. Hibiscus calyphyllus is a day-blooming species: its flowers open several hours after sunrise and close several hours before sunset. No hybrids involving Hibiscus calyphyllus have been reported to date. However, Hibiscus syriacus and Hibiscus calyphyllus share an identical diploid chromosome count of 80. The Maasai people of Kenya use this plant to construct huts.
