''Rhipsalidopsis gaertneri'',

synonyms A synonym is a word, morpheme, or phrase that means precisely or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are a ...

''Schlumbergera gaertneri'' and ''Hatiora gaertneri'', is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

epiphytic An epiphyte is a plant or plant-like organism that grows on the surface of another plant and derives its moisture and nutrients from the air, rain, water (in marine environments) or from debris accumulating around it. The plants on which epiphyt ...

cactus which belongs to the tribe

Rhipsalideae The Rhipsalideae are a small tribe of cacti, comprising four or five genera (and around 60 species). They grow on trees (epiphytes) or on rocks (lithophytes), where they either hang down or form creeping or upright shrubs. Their flowers open in ...

within the subfamily

Cactoideae The Cactoideae are the largest subfamily of the cactus family, Cactaceae, and are widely distributed throughout the Americas. Cactaceae is the 5th most endangered plant or animal family evaluated globally by the International Union for Conservati ...

of the

Cactaceae A cactus (: cacti, cactuses, or less commonly, cactus) is a member of the plant family Cactaceae (), a family of the order Caryophyllales comprising about 127 genera with some 1,750 known species. The word ''cactus'' derives, through Latin, ...

. Together with the hybrid with '' R. rosea'', ''Rhipsalidopsis'' × ''graeseri'', it is known, in English speaking countries in the Northern Hemisphere, as Easter cactus or Whitsun cactus and is a widely cultivated ornamental plant. It has received the

Royal Horticultural Society The Royal Horticultural Society (RHS), founded in 1804 as the Horticultural Society of London, is the UK's leading gardening charity. The RHS promotes horticulture through its five gardens at Wisley (Surrey), Hyde Hall (Essex), Harlow Carr ...

Award of Garden Merit The Award of Garden Merit (AGM) is a long-established award for plants by the British Royal Horticultural Society (RHS). It is based on assessment of the plants' performance under UK growing conditions. It includes the full range of cultivated p ...

Description

''Rhipsalidopsis gaertneri'' is found in southeastern

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

, in Paraná and Santa Catarina, at altitudes of . ''R. gaertneri'' grows on trees (

) or less often rocks ( lithophytic) in sub-tropical rain forest. With maturity, it develops into a branching pendant leafless shrub with a woody base. The stems are made up of segments, most of which are flattened and which are the

photosynthetic Photosynthesis ( ) is a Biological system, system of biological processes by which Photoautotrophism, photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical ener ...

organs (

cladode Phylloclades and cladodes are flattened, photosynthesis, photosynthetic shoots, which are usually considered to be modified branches. The two terms are used either differently or interchangeably by different authors. ''Phyllocladus'', a genus of ...

s) of the plant. Younger segments are dullish green, long and wide, with small notches on the margins. Structures characteristic of cacti, called

areole In botany, areoles are small light- to dark-colored bumps on cactus, cacti out of which grow clusters of Thorns, spines, and prickles, spines. Areoles are important diagnostic features of cactus, cacti, and identify them as a family distinct fr ...

s, form in these notches. Flowers form from areoles at the ends of the stems. These are scarlet in colour, long, radially symmetrical (actinomorphic), opening to a funnel shape with a maximum diameter of about . Red oblong

fruit In botany, a fruit is the seed-bearing structure in flowering plants (angiosperms) that is formed from the ovary after flowering. Fruits are the means by which angiosperms disseminate their seeds. Edible fruits in particular have long propaga ...

s form after the flowers are fertilized.

Taxonomy

Although cacti belonging to the tribe Rhipsalideae are quite distinct in appearance and habit from other cacti, as they grow on trees or rocks as epiphytes or lithophytes, for a long time there has been confusion as to how the species should be placed into genera. ''Rhipsalidopsis gaertneri'' was first described in 1884 by Eduard von Regel as the variety ''gaertneri'' of ''Epiphyllum russellianum'' (now ''

Schlumbergera russelliana ''Schlumbergera russelliana'' is a species of plant in the family Cactaceae. It is Endemism, endemic to a small area of the coastal mountains of south-eastern Brazil where its natural habitat is moist forest. It grows on trees as an epiphyte. It ...

''). The name honours one of the Gaertner family, early settlers in

Blumenau Blumenau () is a city in Vale do Itajaí, Santa Catarina (Brazil), Santa Catarina state, in the South Region, Brazil, South Region of Brazil, from the state capital Florianópolis. The city was founded by the German chemist and pharmacist H ...

.Arquivo Histórico José Ferreira da Silva

/ref> The species has had a complex taxonomic history. In 1889, William Watson (19th century botanist), William Watson elevated it to the full species ''Epiphyllum gaertneri'' and in 1913, Nathaniel Britton and Josephy Rose transferred it to ''

Schlumbergera ''Schlumbergera'' is a small genus of cactus, cacti with six to nine species found in the coastal mountains of south-eastern Brazil. These plants grow on trees or rocks in habitats that are generally shady with high humidity, and can be quite d ...

'' as ''S. gaertneri''. The relationship to ''S. russelliana'' was based on the appearance of the stems, made up of somewhat flattened segments with small teeth, and the radially symmetrical shape of the flowers. However, the deeper structure of the flower differs from ''Schlumbergera'' species, which have a short floral tube at the base of the flower formed by fused petals, and stamens arranged in two distinct series, whereas ''Rhipsalidopsis gaertneri'' has separate petals and a single series of stamens. ''Rh. gaertneri'' was separated from ''Schlumbergera'' as ''Rhipsalis gaertneri'' by Friedrich Vaupel in 1925, after which it was successively transferred to ''Epiphyllopsis'' by

Alwin Berger Alwin Berger (28 August 1871 – 20 April 1931) was a German botanist best known for his contribution to the nomenclature of succulent plants, particularly agaves and cacti. Born in Germany he worked at the botanical gardens in Dresden and Fra ...

in 1929, ''Rhipsalidopsis'' by Karl Hermann Leonhard Lindinger in 1942, and ''Hatiora'' by

Wilhelm Barthlott Wilhelm Barthlott (born 22 June 1946 in Forst, Germany) is a German botanist and biomimetic materials scientist. His official botanical author citation is Barthlott. Barthlott's areas of specialization are biodiversity (global distribution, a ...

in 1987. It was put back in ''Schlumbergera'' as the result of

molecular phylogenetic Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

studies in 2011, and then restored to ''Rhipsalidopsis'' again. In horticultural sources, the Easter cactus continued to be referred to as ''Schlumbergera gaertneri'' (even when other sources placed it in ''Hatiora''), as well as ''Rhipsalidopsis gaertneri''.

Cultivation

Under the name Easter cactus or Whitsun cactus, ''Rhipsalidopsis gaertneri'' is widely cultivated as an ornamental plant for its scarlet flowers. Its common names reflect the period in which it flowers in the

Northern Hemisphere The Northern Hemisphere is the half of Earth that is north of the equator. For other planets in the Solar System, north is defined by humans as being in the same celestial sphere, celestial hemisphere relative to the invariable plane of the Solar ...

, namely late Spring. It has been artificially crossed with a pink-flowered species, '' Rhipsalidopsis rosea'', to form the hybrid ''Rhipsalidopsis'' × ''graeseri'',

cultivar A cultivar is a kind of Horticulture, cultivated plant that people have selected for desired phenotypic trait, traits and which retains those traits when Plant propagation, propagated. Methods used to propagate cultivars include division, root a ...

s of which have flowers in a wider range of colours. The Easter cactus is considered more difficult to grow than the Christmas or Thanksgiving cactus (cultivars and hybrids of ''

''). Recommendations for care include: * ''Temperature'' Summer temperatures around are suggested, with lower temperatures down to in the winter (November to January in the Northern Hemisphere) to initiate good bud formation. * ''Light'' As epiphytic forest plants, they are not exposed to strong sunlight. Half-shade is recommended; plants can be placed outside in the summer., p. 74 * ''Watering'' The Easter cactus is said to respond badly to over- or under-watering, e.g. by losing stem segments; continuously moist soil is recommended. * ''Propagation'' Stem segments may be removed in late Spring and the cut surface allowed to dry out before being placed in slightly moist soil.

References

Bibliography

* {{Taxonbar, from1=Q3153249, from2=Q138282 Rhipsalideae Cacti of South America Endemic flora of Brazil Flora of the Atlantic Forest Flora of Paraná (state) Flora of Santa Catarina (state) Plants described in 1884 Epiphytes Garden plants of South America