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Products > Thunbergia gregorii
Thunbergia gregorii - Orange Clock Vine
Image of Thunbergia gregorii
Habit and Cultural Information
Category: Vine
Family: Acanthaceae (Acanthus¹)
Origin: Africa, Central (Africa)
Evergreen: Yes
Flower Color: Orange
Bloomtime: Year-round
Synonyms: [Thunbergia gibsonii]
Height: Climbing (Vine)
Width: Spreading
Exposure: Full Sun
Seaside: Yes
Deer Tolerant: Yes
Irrigation (H2O Info): Low Water Needs
Winter Hardiness: 25-30° F
TThunbergia gregorii (Orange Clock Vine) - An evergreen vine that grows to 8-10 ft. tall or, if without support, can become an extensive groundcover. On several inch long slightly winged petioles are the 1 inch long triangular leaves with hastate bases and toothed margins that are sparsely hairy. The bright, pure orange flowers are present year-round in coastal California gardens.

Plant in full sun and water only occasionally. This vine is cold hardy to 25 degrees F and will come back from the ground if nipped by even colder temperatures. It makes a great chain-link fence climber or a ground cover and it tolerant of near coastal conditions.

Thunbergia gregorii comes from tropical Africa, from south Ethiopia to Burundi and Tanzania. The name for the genus honors the Swedish naturalist Carl Peter Thunberg (1743-1828) who was a student of Linnaeus and spent several years botanizing the Cape of Good Hope. This plant is similar to its more tender South African relative, the Black-Eyed-Susan Vine Thunbergia alata but Thunbergia gregorii is easily disguisable by its lack of the dark-centered eye of the flower and the much narrower flattened "wings" on the petioles. Thunbergia gregorii also only has orange colored flowers while Thunbergia alata cultivars can be found in a range of colors from pink to yellow and even those with bicolored picotee flowers, but always with a dark eye.

Another similar plant is one described as Thunbergia gibsonii that has long been listed in cultivation in California. The two names were considered by some to be synonymous but both plants were described as distinct species by the English botanist Spencer Le Marchant Moore (1850–1931) in 1894 in the Journal of Botany, British and Foreign (Vol. 32). The most recent treatment has Thunbergia gibsonii, a narrow endemic found only at a single location in central Kenya, as a valid species that differs in having larger yellow orange colored flowers, longer ovate leaves on shorter non-winged petioles that are more pubescent with white or yellow hairs as opposed to Thunbergia gregorii with slightly smaller richer orange colored flowers, leaves that are sagittate-ovate leaves in shape that are sparsely hairy with orange hairs and are held on long petioles that are slightly winged (though less so than T. alata). There has long been confusion between these two species and it is not clear whether Thunbergia gibsonii is currently still in cultivation in California. The genus name honors the Swedish physician and botanist, Carl Peter Thunberg (1743-1828), who was a protégé of Linnaeus and Moore reportedly named Thunbergia gregorii to honor his colleague John Walter Gregory (1864-1932), a Scottish explorer and paleontologist. It was on Gregory's travels from 1892-1893 when he explored the Great Rift Valley that he collected the type specimen of Thunbergia gregorii. Moore named Thunbergia gibsonii after a "Mr. Gibson" who collected seed of the plant in Kenya when on the Captain Frederick Lugard's expedition in Uganda and Kenya. He reportedly only found the plant in one location at around 8,000 feet in elevation where it was growing in "wet swampy ground amidst hills". Thunbergia gregorii was introduced into the California nursery trade by Hugh Evans at his Evans and Reeves Nurseries and Thunbergia gibsonii was reportedly introduced in 1920 by Edward Owen Orpet, the City of Santa Barbara's Superintendent of Parks and namesake of Orpet Park in the city's Riviera. We have grown Thunbergia gregorii since 1980 and it graces several fence lines in the nursery. 

This information about Thunbergia gregorii displayed is based on research conducted in our horticultural library and from reliable online resources. We also will relate observations made about it as it grows in our nursery gardens and other gardens we have visited, as well how the crops have performed in containers in our nursery field. We will also incorporate comments that we receive from others and we welcome hearing from anyone with additional information, particularly if they can share any cultural information that would aid others in growing it.