''Thunbergia alata'', commonly called black-eyed Susan vine,
is a herbaceous perennial climbing plant species in the family
Acanthaceae
Acanthaceae is a family (the acanthus family) of dicotyledonous flowering plants containing almost 250 genera and about 2500 species. Most are tropical herbs, shrubs, or twining vines; some are epiphytes. Only a few species are distributed in tem ...
. It is native to
Eastern Africa
East Africa, Eastern Africa, or East of Africa, is the eastern subregion of the African continent. In the United Nations Statistics Division scheme of geographic regions, 10-11-(16*) territories make up Eastern Africa:
Due to the historica ...
, and has been naturalized in other parts of the world.
It is grown as an
ornamental plant
Ornamental plants or garden plants are plants that are primarily grown for their beauty but also for qualities such as scent or how they shape physical space. Many flowering plants and garden varieties tend to be specially bred cultivars that ...
in gardens and in hanging baskets. The name 'Black-eyed Susan' is thought to have come from a character that figures in many traditional ballads and songs. In the ''Ballad of Black-eyed Susan'' by
John Gay, Susan goes aboard a ship in-dock to ask the sailors where her lover
Sweet William has gone. Black-eyed Susan is also a name given to other species of flowers in the genus ''
Rudbeckia
''Rudbeckia'' () is a plant genus in the Asteraceae or composite family. Rudbeckia flowers feature a prominent, raised central disc in black, brown shades of green, and in-between tones, giving rise to their familiar common names of coneflowers a ...
''.
Description
''Thunbergia alata'' has a vine habit, and can grow to a height of high in warmer zones, or much less as a container plant or as an annual. It has twining stems with heart or arrow-shaped leaves. The three and a half to seven and a half centimeters long and two and a half centimeters wide leaves are triangular to heart-shaped. Their edges are wavy and both surfaces are hairy. The
leaf blade
A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, ste ...
s sit on up to six and a half centimeters long
petioles, which attach at a distance of four and a half to 13 centimeters on the one to one and a quarter millimeter thick stem axis.
Inflorescence
The hairy, mostly orange-yellow flowers have five petals and appear throughout the growing season, which grow on up to eight and a half centimeters long
inflorescence
An inflorescence is a group or cluster of flowers arranged on a Plant stem, stem that is composed of a main branch or a complicated arrangement of branches. Morphology (biology), Morphologically, it is the modified part of the shoot of sperma ...
axes. They typically are warm orange with a characteristic dark spot in the centre. The central two centimeter long
corolla tube is black-violet. Each of the single flowers has two triangular to oval, hairy
bracts that taper towards the outside. They are 18 to 20 millimeters long and nine to ten millimeters wide. The serrated
calyx is about two millimeters long and has between 15 and 17 awl-shaped lobes. The corolla tube measures around four centimeters and shows five two centimeter large corolla lobes with right-hand covering
buds on the outside.
The 16 to 18 millimeter long fruits are finely hairy. At the base they have a diameter of seven millimeters. The four seeds measure 3.5 millimeters.
Cultivation
''Thunbergia alata'' seed is easy to germinate in humus-rich soil with some sand and it can be grown from
cuttings. Soaking the seeds in a dish of warm water over night will help improve seed germination when planted. It is a fast grower, blooming quickly, with light trimming encouraging more blossoms.
There are cultivars with red, orange, red-orange, white, pale yellow, or bright yellow flowers, with or without the characteristic chocolate-purple centre which inspires the common name.
Distribution
The plant is originally from East Africa, and has almost a world distribution including tropical and subtropical areas like China, eastern
Australia,
Hawaii
Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only state ...
,
Southern US
The Southern United States (sometimes Dixie, also referred to as the Southern States, the American South, the Southland, or simply the South) is a geographic and cultural region of the United States of America. It is between the Atlantic Ocean ...
in the states of
Texas
Texas (, ; Spanish: ''Texas'', ''Tejas'') is a state in the South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2020, it is the second-largest U.S. state by ...
and
Florida
Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...
,
Colombia,
Puerto Rico
Puerto Rico (; abbreviated PR; tnq, Boriken, ''Borinquen''), officially the Commonwealth of Puerto Rico ( es, link=yes, Estado Libre Asociado de Puerto Rico, lit=Free Associated State of Puerto Rico), is a Caribbean island and unincorporated ...
,
Mexico, South Africa, Portugal, Japan, New Zealand,
Cerrado
The ''Cerrado'' (, ) is a vast ecoregion of tropical savanna in eastern Brazil, particularly in the states of Goiás, Mato Grosso do Sul, Mato Grosso, Tocantins, Minas Gerais, and the Federal District. The core areas of the Cerrado biome are the ...
vegetation
Vegetation is an assemblage of plant species and the ground cover they provide. It is a general term, without specific reference to particular taxa, life forms, structure, spatial extent, or any other specific botanical or geographic characte ...
of
Brazil
Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
, Argentina, Madagascar, India, Thailand and Philippines, among others.
It is used all around the world as a garden plant, but has managed to "
escape
Escape or Escaping may refer to:
Computing
* Escape character, in computing and telecommunication, a character which signifies that what follows takes an alternative interpretation
** Escape sequence, a series of characters used to trigger some so ...
" to the wilderness, naturalizing in tropical and temperate forests. It has been widely reported as
Invasive species, especially in the
Caribbean and
Pacific islands, from Mexico to Colombia, and in Japan, due to the fast growing of the plant; the ease of wild
pollination
Pollination is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by wind. Pollinating agents can be animals such as insects, birds, a ...
during sporadic flowering times; its vine-growing strategies that strangle or create shadow on other plants; its difficulty to eradicate by hand (as it leaves underground rhizomes that rapidly grow back); its lack of usual
predator
Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...
s in non native regions; plus, people who are unaware of its harmful nature to other plants in the wilderness tend to admire its beauty and might opt not to remove it.
Gallery
Starr 070308-5462 Thunbergia alata.jpg, Flowers and leaves
Thunbergia alata - Flower - bract removed.jpg, Flower (bract removed)
Thunbergia trellis.jpg, A young plant being trained to grow on a trellis feeder wire
Thunbergia alata20090902 86.jpg, Seed - diameter is appr. 4 mm.
Starr_071024-0311_Thunbergia_alata.jpg, Yellow flower variety
Thunbergia alata, Hungary.jpg, As a porch plant
Starr 070308-5465 Thunbergia alata.jpg, Vigorous growth
Starr 080219-2901 Thunbergia alata.jpg, Maui, Enchanting Floral Gardens of Kula
References
External links
Atlas of Florida Vascular Plants: ''Thunbergia alata''
*
*
{{Taxonbar, from=Q161248
alata
Flora of Africa
Flora of Southern Africa
Garden plants of Africa
Creepers of South Africa
Flora naturalised in Australia
Taxa named by Wenceslas Bojer
Taxa named by John Sims (taxonomist)