The Oncidium Section Variegata or Equitants
"The Tolumnias"


The Oncidium Section of the genus oncidium has received considerable attention from breeders and growers over recent years, and plants from this Section are now becoming increasingly popular, both overseas and in this country. This Section, both species and hybrids, is more commonly known as the Variegata or Equitants. They ahve now been seplarated into their own genus - Tolumnias 46.

The plants are small and compact, producing sprays of many, generally brilliantly coloured, flowers. They are without pseudobulbs, growing in an attractive fan-like shape with their triangular section leaves overlapping at their bases. Their compact habit, bright and long lasting flowers means that they can be readily accommodated in most collections, even where space is limited. Rasputin9 states that typically the flower sprays of the hybrids are some 250 to 400 mm long, bearing 6 to 10 flowers, each about 25 mm across.


The features which characterise the plants from this Section are their somewhat fleshy sepals. The petals and lip, excluding callosities, are membranaceous. Pseudobulbs are inconspicuous, poorly developed with a terminal and aborted appendage in lieu of a developed leaf. The lateral sheaths are all leaf bearing, in two rows. Leaves are triangular in cross section, showing a finely serrated edges.2

Most of the speices come from the lowland rainforest habitat although some show adaaptatiosn that are applicable to the dry inland habitats. The habitat information can be usefully refeerred to for more information.


BREEDING AND DEVELOPMENT


The original species were quite modest plants, and were considered of botanical interest only by many. W.W. Goodale Moir of Hawaii, who has been largely responsible for the development of many of the present day hybrids, was in the early years accused of breeding weeds. The development and improvement which has taken place has occurred only over the last thirty odd years, a relatively brief period by orchid breeding standards. In a article 10 Moir stated that "if (he) had not visited many of the islands of the Caribbean and observed these little orchids many times in great masses of flowers, and seen their special beauty (he) doubted if (he) would have taken on their breeding." "The beauty and colour of the present day hybrids did not appear in the species except in small areas of the flowers. (He) saw these small areas of colour and worked them together to make larger areas and designs, and beauty resulted. This can be done with any set of flowers, but one must learn dominance and recessiveness, and how to combine those traits of the several good species. It is like painting a picture; you plan, you sketch, you mix the paints." 10 The quality of the present day hybrids particularly speak of the success of Moir's breeding program.

Moir discovered early in his breeding that certain plants would not breed, or were reluctant breeders. It was subsequently discovered that species of the Variegata contained different chromosome numbers; diploid counts of 40, 42 and 84 being present naturally.l2 This restricted progress as chromosome incompatibility caused many crosses to fail. Rasputin9 reports that prime crosses (crosses between two species) having the same chromosome count, gave a success rate in producing flowering progeny of 50 to 60%. With the crossing of 40 and 42 chromosome species, this dropped to only 25 to 30%. Crosses between 84 and 42 chromosome plants were successful on less than 25% of attempts. Some of these last crosses were however successful, such as the hybrid Golden Glow, which is a triploid, having 63 chromosomes, and which was valuable for further breeding. Subsequent generations had a success rate of only around 20%, but often the progeny that were produced were very good, and some would breed on to enable improvement to be continued. It will be obvious from the above that progress has not been easy, but persistence and a scientific approach, in particular involving cytological studies, has produced its rewards. With many species in existence which have not been widely utilised to date, exciting possibilities exist for further breeding.

It is also relevant to note that Moir10 believes that because of the breeding affinity between Variegata, but lack of affinity to other oncidiums, they should perhaps be considered as a genus separate from true oncidiums. He also reports that members of Variegata have not generally been successful outside their own group as when crossed with other oncidiums, they have lost their identity. In crosses, for example, with rodrigueza (and other genera), they were almost completely taken over in shape by the other genus of the bigeneric.

Moir10 has also found that great variation can occur within any cross, and also between clones of a species. Some have flowers two to three times larger than the average. It is also reported that some are very much better breeders than others, and impart different traits to their hybrids. Rasputin9 notes that as some of the more advanced hybrids are quite 'mixed-up' genetically, sibling plants can range in colour from lavender, to yellow, to orange, to white, with variations in colour intensity, patterns, shapes and designs. "Few plants of each cross can be expected to be of 'Award Quality', . . . but even the 'mediocre' ones have great charm." If plants of the same cross are purchased, it is therefore apparent that significant differences in the flowers can be anticipated; a point worth remembering when purchases are being made, especially if few crosses are available.


THE SPECIES


It may be of assistance in understanding the Variegata if something is known of the species which have been used in the breeding of the present day hybrids. The main species utilised in the creation of what are now considered the best hybrids are urophyllum, pulchellum, triquetrum, henekenii and guianense, in order of decreasing importance.10

Onc. urophyllum is described by Hawkes1 as having leaves 100 to 150 mm long. The inflorescence is slender, erect or arching, to 600 mm long, many flowered on a branched panicle, the flowers often appearing successively over a long period of time. The individual flowers are less than 25 mm in diameter, yellow, and blocked chestnut brown. Spring to summer flowering, he reports it is native of the Lesser Antilles. Berlinerl3 notes that it grows on twiggy branches in considerable light and air movement, with quite rampant growth. It also produces abundant keikis from the inflorescence after flowering. Rasputin9 mentions very tough growing conditions, where intermittent dry periods and high winds are experienced. An 84 chromosome species, its yellow colour and broad full lower lobe are very dominant, making large full flowers in subsequent generations. In breeding its long peduncle bred larger peduncles than was generally desired in some cases, this being its one fault.10

Onc. urophyllym Onc. pulchellum

Onc. pulchellum16 has 75 to 125 mm long fleshy leaves, acutely keeled behind. The inflorescence is slender, erect to 375 mm tall, 12 to 20 flowers or more, not branched. Flowers are about 25 mm long, extremely variable in colour (and somewhat in dimensions) white, more or less flushed rose or lilac-rose on all segments. Mostly summer flowering, it is native of Cuba, Jamaica, Hispaniola, and the Guianas. I Reportedi3 to grow on twiggy branches in considerable light and air movement, its roots cling to these twigs, and sometimes extend 300 mm or more from the base of the plants. This species has the largest flowers of the Variegata and also has a broad shouldered lip base which is of value in breeding.10

Rasputin9 comments that this 42 chromosome species grows in milder conditions and more stable humidity than urophyllum.

Onc. triquetrum16 has three to four leaves, fleshy, 75 to 125 mm long. The inflorescence is slender, to about 175 mm long, often producing accessory racemes for more than one season. The 5 to 15 flowers, each about 12 mm long, are long lasting. The sepals are purplish-green, the petals white, tinged pale green and spotted with purple. The lip is white, spotted and streaked with purple or reddish-purple. Mostly summer flowering, but often ever blooming, it is endemic to Jamaica.1 It is found growing at low elevations, mainly on the mossy trunks of old mango trees. It differs from most equitants in preferring shade and moist conditions.13

Onc. triquetrum

It has been widely used in breeding, one of its more important characteristics being to reduce the length of peduncles, especially where pulchellum is also involved. It also increases branching and repeated re-flowering on the same peduncle of its hybrids. It did however reduce the size of the flowers, and often caused these to be closer together than was desirable.10 This is a 42 chromosome species.9

Onc. henekennii. Northen14 describes the lip of this species as looking like a spider, so much so that the people of its native Hispaniola call it the "spider" or "tarantula" orchid. She reports that it grows in a warm dry environment. A 40 chromosome plant, it gave fascinating red flowers in breeding because underlying its black is a red colouration. Its progeny invariably show a broad isthmus odd crest, and widely shaped flowers.10 The use of this species usually produced somewhat elongated, vertically rectangular flowers, in contrast to the more rounded flower form of the other Variegata species. 13

It is reported to grow in a compact form with bronzed leaves in tough growing conditions.7 This plant thrives in maximum light, and requires light watering. ". . . if you think it needs water, perhaps you ought to get to it the following week!!''13

Onc. guianense (also known as desertorum, sometimes referred to as intermedium although these two names appear to be invalid) contains a number of colour forms. Var. alborubrum has petals which are white, with deep red to orange-red bases. The labellum is also deep red or orange-red, with the upper lobes near the base of the callus tessellated with white and orange-red markings. The var. album is white with a yellow callus. The var. aureorubrum has a flower almost identical in colour pattern to the variety alborubrum, but instead of white it is yellow. It is native of the islands of Hispaniola (Haiti and the Dominican Republic) and grows more robustly at higher elevations, in habitats that do not dry out to the extent experienced by some of the plants inhabiting semi-arid situations15

A 40 chromosome species, it shows a great range of variation between clones, in form, size of flower, colour of plant and length of peduncle, and in addition, in colour variants with particular segregation in breeding, making the results exceedingly variable, but very interesting.10

The Dictionary of Gardening6 describes intermedium as having yellow flowers, marked along the back with red spots. The flowers are about 18 mm across, the lip brighter, spotted with red. The spike is 250 mm long, having about six flowers, flowering in summer, and is of a very dwarf growing habit.

A 'full' list17 of species with brief descriptions follow. Withner17 lists in total 26 as compared with Moir's12 34, although Withner shows several groupings which include forms others consider as separate species. The dates of the original species descriptions are shown. It is interesting to note some are amongst the earliest described orchidaceous plants, with quite a number only relatively recently discovered and described. Species listed by Garay and Stacy2 are marked "*" which total 34.

Onc. arizajulianum* (1967) comes from the Dominican Republic, and has red brown markings on a white flower.

Onc. bahamense* (1920) is a nearly terete leaved plant that scrambles in grass clumps, brush and scrub. It is native of the Bahamian Islands and Eastern Florida. An 84 chromosome plant, it is closely related to variegatum.

Onc. calochilum* (1910) has miniature terete leaves, yellow flowers without markings, and a fringed lip. It is a desert inhabitant of Hispaniola and the Cayman Islands, and has a fragrance of roses. Chromosome numbers of 40 and 42 have been reported.

Onc. caribense* (1973), with small yellow flowers with brown markings; very rare.

Onc. caymanense* (1968) from the Cayman Islands, has 2 to 5 pink flowers, is poorly known.

Onc. compressicaule* (1966) sometimes confused with guianense, is a robust species having large panicles of golden flowers with red markings. Native of the Dominican Republic, it occurs in moist cool situations conducive to moss and lichen growth.

Onc. gauntlettii* (1964) a small species from Jamaica has very pale pink or lavender flowers, 1 to 4 in number.

Onc. guianense* (1973) has yellow flowers, and is native of Hispaniola. The forms alborubrum, album and aureorubrum listed by Moir 12 are considered subspecies by Withner. 17

Onc. haitiense* (1922), a yellow flowered species relatively rare in cultivation, is found in the Dominican Republic in desert areas. Moir's jimenezii* is considered a synonym by Withner.

Onc. hawkesianum* (1967) is a small plant with pale pink petals and sepals, and brighter lip, and comes from the Cuban Oriente. It is stated as requiring full sun for flowering. One of the smallest vegetatively of the Variegata, it is reported as having 133 chromosomes.

Onc. henekenii* (1955) from Hispaniola has single flowers occurring successively at the end of the flower spike.

Onc. lemonianum * (1835) has also been called guibertianum *, is native of Cuba. It has semi-terete leaves, bright yellow flowers, and is rare in cultivation.

Onc. lucayanum* (1920) comes from the Bahamas, and grows on scrub on the edges of beaches, or on mangrove swamps, in close proximity to salt water. A very variable species, flower colour ranges from white with purple and brown markings to yellow with red, and has a number of named colour forms; var. aureum, purpureum, and rubiginosum.

Onc. lyratum* (1967) from Cuba, has dark reddish orange flowers, and may be only a colour form of lucayanum.

Onc. moirianum* (1972), a Cuban species with white flowers marked with red. A 40 chromosome plant, rare in cultivation.

Onc. osmentii* (1967) from Hispaniola, is a miniature yellow flowered type and grows under arid sunny conditions on dwarf thorny shrubs on hillside habitats. Related to quadrilobum it is considered by some to be a natural hybrid between that species and haitiense 7 and is listed as such by Sander.18

Onc. prionochilum* (1922) native to the Virgin Islands, has very long flower spikes (up to 3 metres!!!) with yellow flowers.

Onc. pulchellum. (1827) has pale rose pink to dark red-purple flowers, and is from Jamaica. It has hybridised in nature with tetrepetalum to form a complex of hybrids. Similar plants which are listed as synonyms are berenyce,* apiculatum,* concavam, * and cuneilabium. * Others in this group are jamaicense, a white to pink natural hybrid between tetrepetalum and pulchellum, shown as Jamaica in Sander's Lists18 hartii, a natural hybrid between pulchellum and concavam; sanctae-anae, a natural hybrid between berenyce and pulchellum, also registered as St. Anne;18 withnerianum, a natural hybrid between berenyce and tetrapetalum, also used by Moir in hybrids as Brownstown.

Onc. quadrilobum (1940), a miniature desert species from Hispaniola with yellow flowers, marked red-brown, has short flower spikes. Under cultivation the buds form, but require a sudden drop of temperature to induce their final development. The spikes can produce several flushes of flowers in this manner. Listed2 as a synonym to leiboldii. *


Onc. sasseri
(1975) a member of the lucayanum complex, is a small plant coming from the Bahamas, having long graceful flower spikes bearing 3 to 7 white lavender to pink flowers, with maroon markings. The plants grow in thickly wooded areas in some shade.

Onc. tetrapetalum* (1806) from Jamaica, is related to variegatum, has white flowers, with some pink forms.

Onc. triquetrum* (1813) from Jamaica, has short horizontally inclined flower spikes bearing flowers of maroon and white colouration. This species is said to intensify colouration in its hybrids.

Onc. tuerckheimii* (1912), a cool growing species from Hispaniola and Cuba, rare in cultivation, has 3 to 9 yellow flowers, with bold chocolate spotting.

Onc. urophyllum * (1842) is from the Lesser Antilles, produces yellow flowers with brown markings.

Onc. usneoides* (1858), a miniature species, but not now in cultivation.

Onc. variegatum* (1800), a diverse assemblage of plants, having flowers with red brown markings on white to pale lavender or rose tepals. It is the most widely distributed of the variegata. A number of varietal forms have been described: roseum, purpureum, album. Species included by Withner in this complex are as follows:

Onc. leiboldii* (1863), a rose or pink coloured form from Cuba and probably other islands. The degree of pinkness is reported to change with variations in light intensity and temperature. Sanders1 lists leiboldii x variegatum as the natural hybrid Cubense.

Onc. scandens (l968), tetraploid Haitian-Hispaniolan plants with white to rose coloured flowers, having semi-terete leaves, and flower stalks which can reach one metre in length. It is said to inhabit pine forests at upper elevations, the long flower stalks necessary to rise above the long grass in which it grows.


Onc. sylvestre (1958) is a Cuban species growing in long grass in leaf debris on the ground. The flowers are light purple.

Onc. velutinum * (1851) is another Cuban species and from Hispaniola, having flowers that vary from all pink or lavender to all white with brown maRkings. Sanders lists velutinum x variegatum as the natural hybrid vervelum, or registered grex Varvel.

On. furcyense (1969) is a natural Haitian hybrid of variegatum and scandens, with deep pink flowers with prominent yellow crest, registered 18 as Jeremie.

The above five "species" are considered subspecies of variegatum by Withner.17

There are three natural hybrids listed by Withner:

ann-hadderiae (1972) = (variegatum x haitiense) in Dominica, registered18 as Les Cayes, light yellow lip, yellow petals with brown bars;

domingense (1969)=(haitiense x scandens) pale pink, from north-west Dominica; and

floride-phillipsee (1967) = (prionochilum x variegatum var. purpureum) having purple coloured flowers on the reverse, yellow with purple edges on the front surface.17

Moir10 states that the 40 chromosome plants haitiense, lucayanum, moirianum and quadrilobum, with guianense and henekenii in hybridising produced fewer widely spaced odd shaped flowers. The spotted flowers of moirianum produced spotted hybrid progeny.

Spots and dots of one colour on another colour are contributed by triquetrum, haitiense, lemonianum and moirianum, although those of the first two are generally much larger and more beautiful because the spots are more widely spread.

The species gauntlettii and tetrapetalum have medium length peduncles. There exists a small compact sub-group with terete leaves, such as caribense, leiboldii, arizajulianum, which are very short stemmed. There is a group with long stemmed spikes, such as compressicaule and prionochilum.

Pulchelluml6 has the largest flowers, followed by urophyllum, quadrilobum, guianense, and variegatum. 17 One species, concavum, is reported to have produced some very dark coloured progeny.

As an increasing number of species are being experimented with in hybridising, the above characteristics may be of interest in considering the outcome of some of these crosses. For those wishing to look further at these plants, Moir's book Breeding Variegata Oncidiums19 is highly recommended.

It is obvious that the taxonomy of this group is still not fully settled, and further study is needed to bring order and some degree of uniformity. It is believed the above comments on the species may be of assistance to those interested in the breeding of these plants, and will give some of the characteristics of the species now recognised. It is interesting that the photos published 17 show considerable visual similarity between many of the species.

 

CULTURE

The discussion of the species will have indicated certain cultural requirements. The various elements relevant to culture of these plants will, however, be discussed separately Where hybrids contain species having different cultural requirements, generally the hybrid will respond to the average, weighted according to the proportion of each species contained in the hybrid.

Hawkes,1 in the species listed in his work, indicates that they require intermediate to intermediate/warm conditions; minimum night temperatures of 12 to 17 oC. The species listed in The Dictionary of Gardening 6 are noted as requiring intermediate to tropical conditions (temperatures not specified) although one, intermedium (presumably guianense), is listed as cool growing. That publication also states that the equitants should receive lower night temperatures in the winter, Rasputin9 noting that plants have been successfully wintered where temperatures have fallen to 3 oC. The only effect of this was to delay the growth and flowering the following spring. Locally, most growers have had more success where some heat is able to be provided, at least initially until they have gained experience with these plants and that they have grown them to reasonable size.

GROWING MEDIA

Moir11 states that it does not matter what the growing media utilised is, as long as it drains well, aerates well, keeps free from fungus and scum, and dries out well between waterings.

Rasputin9 emphasises conditions allowing quick drying, with much air movement over the entire plant, including the root system. He recommends small pot culture utilising an extremely open media, or growing the plants as epiphytes, mounted on pieces of bark, cork, wood or similar.

Berliner13 favours slab culture, with the plants mounted on thin slices of tree-fern, or on braches of wood tied on with thin mono-filament fishing line. He recommends mounting on slabs of sphagnum moss, to slow somewhat the drying around the roots, but which also allows good aeration, while supplying a humidity source. If sphagnum moss pads are used, however, watch that this does not break down forming a dense mat of material which can cause the roots (and even the plant) tc die, after a period of time. Often such pads can be retained for 6 - 9 months until a strong new root system has developed, then carefully removed.


WATERING

Berliner13 states watering at least once every day under sunny conditions is required, and sometimes twice or even more on hot summer days. His aim is for the plants to be completely dry one hour after watering, this ensured by maintaining rapid air movement over the plants. This requirement is confirmed by other growers.


Watering schedules are dependent on the humidity levels of the growing area, and must be adjusted accordingly. Most watering is required in the summer when humidity is lower, and plant growth is at the highest level.


HUMIDITY

50 to 60% humidity should be maintained if at all possible.13 Cold damp conditions with little air movement are conducive to loss of plants through rot, or at the least will inhibit root growth.9 The general rule would apply: if you grow your plants under cooler conditions, grow them somewhat drier than would otherwise be the case.

SHADING

Berliner13 states that most of the present day complex hybrids require similar conditions to those required by the species urophyllum and pulchellum. Most of the plants require a relatively high light intensity for good growth and flowering as well as for longevity and freedom from rot and other diseases. He states he grows under diffused light with a summer intensity of around 4000 to 5000 foot candles. Rasputin9 also emphasises bright lighting conditions although he states direct sunlight may cause problems through burning of the foliage.

FERTILISING

As epiphytes, the plants can be expected to require little fertiliser, as in their natural environment they could be expected to receive a relatively low level of nutrients. Berliner13 reports he uses very dilute (half teaspoon per 5 litres) of 20:20:20 fertiliser once weekly on epiphytically mounted plants. He has also utilised the mix daily, interspersed with an organic fertiliser with the same dilution. He states that the plants appear to respond to this program, although does not recommend it for plants in pot culture. Such container grown plants could however be expected to respond to weak applications, although the build up of salts in the pots and media would have to be guarded against; the flushing of the containers with plenty of fresh water every few weeks is necessary.

Northenl4 recommends a fertilising program for oncidiums similar to that practised for cattleyas, and this would be suitable for the Variegata. Berliner13 recommends dilute applications and suggests the use of "fish emulsions", or products containing a comprehensive selection of trace elements, is beneficial.

GENERAL

Moir11 reports crosses could flower in two to four years, therefore even when small plants are purchased, flowers can be expected reasonably quickly, as compared with some other orchid genera. For those able to succeed with these plants and especially for those with restricted space, they make ideal additions to any collection.

The plants are reported to be quite easy to grow provided the main cultural points noted above are followed. Pests and diseases are not reported to be a significant problem when correct culture is being applied.

Do not cut the bloom spikes after the Variegata has bloomed and the flowers have died. Many Variegata will branch after flowering and produce more flowers; therefore cut the spike only after it has turned yellow. 10

Remember, growing orchids is all about enjoying your plants
and sharing your growing success with friends and family.

Good luck and good growing.

   
   
 

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 Site established 9th May 1998
Oncidium series first uploaded 20 October 1999