Pladaroxylon | |
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Pladaroxylon leucadendron [1] | |
Scientific classification | |
Kingdom: | Plantae |
Clade: | Tracheophytes |
Clade: | Angiosperms |
Clade: | Eudicots |
Clade: | Asterids |
Order: | Asterales |
Family: | Asteraceae |
Subfamily: | Asteroideae |
Tribe: | Senecioneae |
Genus: | Pladaroxylon Hook.f. |
Species: | P. leucadendron |
Binomial name | |
Pladaroxylon leucadendron | |
Synonyms [3] | |
List
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Pladaroxylon is a genus of trees in the tribe Senecioneae within the family Asteraceae.
The only known species is Pladaroxylon leucadendron, native to the island of St. Helena in the South Atlantic. Commonly known as the he cabbage-tree.
Pladaroxylon leucadendron is a small tree, growing to a maximum of 5 meters in height, with relatively large and cabbage like leaves. [4] [5] On young trees the leaves are very large, often reaching 30 centimeters in length, but on older trees they are usually smaller. They are oval in outline, with a downy underside, and very prominent veins. [6]
The trees branch at regular intervals into two equal sized limbs and all the leaves are at the furthest ends of the branches. [4] The first branching is at 1.2–2 meters above the ground. The tree has a broad, rounded canopy when full grown. [6]
As typical of the family it has flower heads ( capitula ) with many flowers crowded together in one structure that resembles a single flower, each about 6 millimeters in width. [6] [4] Each of these flower heads grows together with many others in a cluster called a corymb. [4] The flower heads have white petals (ray flowers) which make the clusters resemble a head of cauliflower and bloom during July. [1]
The species was given its first scientific description in 1803 by Carl Ludwig Willdenow, however he named it as Solidago leucadendron, the same name previously given by Georg Forster to the species now known as Senecio leucadendron making it a botanical illegitimate name. [7] It was then described in 1838 by Augustin Pyramus de Candolle with the name Lachanodes leucadendron. The same year, but slightly later, Stephan Endlicher described it and named it Lachanodes pladaroxylon. [3] The genus Pladaroxylon was named by Joseph Dalton Hooker in 1870, [8] when he moved the species to its own genus. [3] [9] It is placed in the tribe Senecioneae in the Asteraceae family. Though this is the same tribe as for the she cabbage-tree their ancestors arrived separately on the island rather than evolving from a common ancestor in their common habitat. [6]
In English the species is commonly known as the "he cabbage-tree", [10] though in 1775 the trees were called the "greater-cabbage-tree" by the inhabitants of the island. [11]
The species is endemic to the Island of Saint Helena. On the island it was only found on the central ridge from 720 to 800 meters. [12] As of 2015 [update] only 55 mature individuals were known to survive in the wild. [2]
The he cabbage-tree is a short lived tree that grows quickly to take advantage of openings in the forest canopy. Due to competition from introduced plants such as bilberry, red cinchona, and New Zealand flax ( Phormium tenax ) it depends on human intervention to make spaces for it to survive. [13] [6] Formerly it formed a part of the native forest and grew at lower elevations than the other species called cabbage trees on the island. [6] Conservation efforts for the he cabbage-tree include the planting of more than 100 seedlings to Diana's Peak National Park, but in 2012 none of the young plants were large enough to reproduce. The very low viability of the tree's seeds hamper efforts at repopulating the species. [13]
Asteraceae is a large family of flowering plants that consists of over 32,000 known species in over 1,900 genera within the order Asterales. The number of species in Asteraceae is rivaled only by the Orchidaceae, and which is the larger family is unclear as the quantity of extant species in each family is unknown. The Asteraceae were first described in the year 1740 and given the original name Compositae. The family is commonly known as the aster, daisy, composite, or sunflower family.
Senecio is a genus of flowering plants in the daisy family (Asteraceae) that includes ragworts and groundsels.
Goldenrod is a common name for many species of flowering plants in the sunflower family, Asteraceae, commonly in reference to the genus Solidago.
Senecioneae is the largest tribe of the Asteraceae, or the sunflower family, comprising over 150 genera and over 3,500 species. Almost one-third of the species in this tribe are placed in the genus Senecio. Its members exhibit probably the widest possible range of form to be found in the entire plant kingdom, and include annuals, minute creeping alpines, herbaceous and evergreen perennials, shrubs, climbers, succulents, trees, and semi-aquatic plants.
Cabbage tree is a common name for several plant species:
The Saint Helena olive is an extinct species of flowering plant. It is the only member of the genus Nesiota. It was endemic to the island of Saint Helena in the South Atlantic Ocean. Despite its name, it is unrelated to the true olive, but is instead a member of the family Rhamnaceae, the family which contains buckthorns and jujube. The last remaining tree in the wild died in 1994, and the last remaining individual in cultivation died in December 2003, despite conservation efforts. It is thus a prime example of recent plant extinction. The Saint Helena olive belongs to the tribe Phyliceae, which are mostly endemic to Southern Africa.
Lachanodes arborea, the she cabbage tree, is a small tree in the family Asteraceae. It is an endangered endemic of the island of Saint Helena in the South Atlantic Ocean. It is now extinct in the wild.
Melanodendron is a genus of trees in the family Asteraceae, with only one species, Melanodendron integrifolium, native to the island of Saint Helena. It is related to the Saint Helenan gumwoods and is the most common of the remaining cabbage tree species of Saint Helena, although it is considered endangered due to the restricted population size.
The flora of Saint Helena, an isolated island in the South Atlantic Ocean, is exceptional in its high level of endemism and the severe threats facing the survival of the flora. In phytogeography, it is in the phytochorion St. Helena and Ascension Region of the African Subkingdom, in the Paleotropical Kingdom.
Commidendrum robustum, the Saint Helena gumwood, is a species of tree endemic to Saint Helena, Ascension and Tristan da Cunha. Though it is now comparatively rare, it was once one of the most abundant trees of mid-elevations of the island of Saint Helena in the South Atlantic Ocean. A small tree to 7–8 m, it was cut extensively for fuel in the early years of settlement of the island by the English East India Company. It has given its name to certain placenames on the island such as "Gumwoods". It is one of several species in the endemic genus Commidendrum.
Mellissia was formerly a monotypic genus in the family Solanaceae with the single species, Mellissia begoniifolia, endemic to the island of Saint Helena. It was named by Joseph Dalton Hooker in honour of John Charles Melliss, a 19th-century engineer and amateur naturalist who worked on Saint Helena.
Solidago canadensis, known as Canada goldenrod or Canadian goldenrod, is an herbaceous perennial plant of the family Asteraceae. It is native to northeastern and north-central North America and often forms colonies of upright growing plants, with many small yellow flowers in a branching inflorescence held above the foliage. It is an invasive plant in other parts of the continent and several areas worldwide, including Europe and Asia. It is grown as an ornamental in flower gardens.
Barringtonia asiatica, also known as fish poison tree, putat or sea poison tree, is a species of Barringtonia native to mangrove habitats from islands of the Indian Ocean in the west to tropical Asia and islands of the western Pacific Ocean.
Asteroideae is a subfamily of the plant family Asteraceae. It contains about 70% of the species of the family. It consists of several tribes, including Astereae, Calenduleae, Eupatorieae, Gnaphalieae, Heliantheae, Senecioneae and Tageteae. Asteroideae contains plants found all over the world, many of which are shrubby. There are about 1,135 genera and 17,200 species within this subfamily; the largest genera by number of species are Helichrysum (500–600) and Artemisia (550).
Lachanodes is a genus of plants in the groundsel tribe of the sunflower family. The plants are native to certain islands in the South Atlantic.
Solidago altissima, the tall goldenrod or late goldenrod, is a North American species of goldenrod in the family Asteraceae which is widespread across much of Canada, the United States, and northern Mexico. It is common in much of its range and fairly tolerant of landscapes which have been disturbed by humans. It has become naturalized in many parts of the world.
Solidago gigantea is a North American plant species in the family Asteraceae. Its common names include tall goldenrod and giant goldenrod, among others.
Solidago houghtonii is a rare North American species of flowering plant in the family Asteraceae known as Houghton's goldenrod. It is native to southern Ontario, Canada and the northern United States. It is threatened by the loss and degradation of its habitat. It is a federally listed threatened species of the United States and it is designated a species of special concern by Canada's Committee on the Status of Endangered Wildlife in Canada.
Scapisenecio pectinatus, synonym Senecio pectinatus, commonly known as alpine groundsel, is a species of flowering plant in the aster family. The species occurs in alpine areas of south-eastern Australia in peat-based soils. It has divided leaves forming a basal rosette and produces a single yellow flower head on a stalk up to 20 cm high.
Senecio leucadendron is a species of flowering plant in the family Asteraceae, endemic to Saint Helena. It was first described by Georg Forster in 1789 as Solidago leucadendron.