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The Oncidium Section CYRTOCHILUM

The Cyrtochilum Section is a large one, with some 51 species listed by Garay and Stacy 2, this number representing over 10% of all oncidium species.

The Section species have flowers that are distinguished by their large size with all floral segments fleshy.2 This caused them to be set apart from many of the other oncidiums when the plants were first described in 1816. While there is some opinion for this distinction to be maintained since Lindley included them in oncidium in 1842, it appears to be generally accepted that separate generic rank is not appropriate, although again more recently their separation into their own genus is now widely accepted..

Many of the plants are quite large, and therefore may not be suitable for smaller glasshouses. They are, however, generally less demanding of heat than some other oncidiums, and therefore are attractive in these days of high heating costs. In the main they are spring/summer flowering, the flowers showing the typical brown and yellow colouration, although some red and white pigmentation also occurs. They produce some of the most handsome and largest flowers of the genus.

THE SPECIES

The species listed 2 are aemulum, annulare, baldeviamae, brachypterum, cordatum, costatum, cryptocopis, detortum, diceratum, engelii, engleranum, falcipetalum, fallens, flavovirens, gargantua, gradiflorum, gyriferum, halteratum, incarum, insculptum, kienastianum, lamelligerum, leopoldianum, loxense, lucescens, ludens, macranthum, mendax, metallicum, microchilum, microxiphium, minax, monachicum, orgyale, pastasae, phylloglossum, plagianthum, rostratum, serratum, simulans, superbiens, tenense, tetracopis, trifurcatum, trilingue, tucumanense, ustulatum, ventilabrum, volubile, xanthedon, and zebrinum.

The majority are native to Peru, Venezuela, Ecuador, Colombia and Guatemala. 1

 

The following descriptions indicate some of the characteristics of plants from the Section.

 Onc falcipetalum is described by Hawkes 1 as producing pseudobulbs 75 to 100 mm long, bearing normally paired leaves 250 - 375 mm long, and about 25-50 mm broad. The inflorescence is stout, bending gently with its three metre length, irregularly branching. Each branch is rather short, and bearing 3 to 5 flowers, which open over a long period of time. The individual flowers are to 75 mm long, the sepals rich russet-brown with a narrow yellow margin, strongly clawed. The dorsal sepal is roundish, the lateral pair egg shaped. The petals are much smaller, sickle shaped, the margins very wavy, yellow, spotted mostly in the basal part with brown. The lip is narrow and comparatively long, purplish-brown in colour, the crest a narrow ridge in front of which is a cluster of sharp tubercules. The column has a horn-like wing on each side of the stigmatic surface. Autumn to early winter flowering, it is a native of Venezuela. This plant was in European cultivation from 1886.6

Oncidium (macranthmn X falcipetalum)

Onc. lamelligerum is a native of Ecuador and has been cultivated since 1871. 6 Williams 7 describes this as a very noble and handsome species with flowers produced on a long branching spike. The dor- sal sepal is kidney shaped, wavy, deep brown in colour, bordered with yellow. The lateral sepals are stalked as is the dorsal, but these are much longer, the bases wedge-shaped on one side. The petals are somewhat arrow-shaped, undulated, pale yellow spotted brown towards the base. The lip has triangular lateral lobes, the mid4obe elongated.7 This plant is summer-flowering. The flower scape can be 2-3 metres long. 6

Onc. macranthum was described by Williams7 in 1894 as being a "magnificent oncidium being one of the handsomest species yet introduced". It has pseudobulbs that vary in size, glossy, 100 to 150 rnm long, 50 to 65 mm in diameter, clustered together. The usually paired leaves are 450 mm long, not very heavily textured. The inflorescence is climbing, viny, to four metres long, paniculate, the branches usually short, each bearing 1 to 4 flowers. Its flowers are probably the largest of the genus, highly variable in all parts, in Certain forms to more than 100 mm across. They are long lasting, with yellow sepals flushed light brown, the petals similar but with their edges more crisped, usually vivid, clear yellow in colour, sometimes flushed pale brown towards the base. The lip is much smaller than the other segments, arrow shaped, with the horn shaped lateral lobes mostly violet-purple, the tongue shaped mid-lobe white. Native of Peru 7 but also in Central America. 6 It is said to occur naturally at high elevations. 7 It has been cultivated since 1867. A number of distinct forms are known. 6 The lists also indicate a number of other species are closely related to macranthum.



Oncidium macranthum

One. serratum is a summer flowering species. It has oval pseudobulbs to 150 mm long, and 45 mm in diameter. The usually two leaves grow to 450 mm long. The inflorescence is wavy, clambering, 2 to 3 metres long, distinctly branched in its upper parts. The 75 mm flowers are very handsome, the sepals chestnut brown with a narrow yellow border. The petals are shorter, more crisped and indented at the apex, the basal two thirds chestnut brown, the apical one third bright yellow. The small tip is purplish-brown.7 It is native of Ecuador and Peru, and has been cultivated since 1850. 6

Moir 8 notes that there are three types of flowers amongst the species included in this Section, as follows:-

 i) Those with perfectly flat, stiff petals at right angles to the dorsal sepals, e.g. aemulum, cordatum, loxense, lucescens, macranthum, mendax, metallicum, minax monachicum, orgyale, ventilabrum, these generally being the most desirable for breeding purposes.
ii) Some have ruffled floppy petals, e.g. lamelligerum

iii) Some have very ruffled petals, which curve around in front of the flower, e.g. falcipetalum, annulare.

CULTURE

Hawkes 1 notes that as the species of this Section are seldom out of growth, they should receive conditions similar to that appropriate for odontoglossums, i.e. relatively cool conditions without temperature extremes. Buoyant but reasonably humid conditions should be aimed at, as the habitat of these plants is at the higher altitudes where cool misting precipitation is the normal.In the main they come from the monsoonal foothill mountain habitat zone.

The -Dictionary of Gardening 6 also confirms that conditions suitable for odontoglossums in the main is best, although some species (lamelligerum, microchilum) will appreciate more warmth, that approaching intermediate conditions.

Williams 7 also confirms cool house culture of these species, as well as a necessity of providing free drainage of the roots. Minimum night temperatures of 10 to 12 oC should be aimed at, although these could be lowered if the plants are kept somewhat drier than normal. As these plants are in continuous growth, and require a constant supply of moisture, a mix (perhaps containing tome sphagnum moss) may be more appropriate as compared with the more freely draining media recommended for the other Sections. Stale media conditions should not, however, be allowed to develop. The maintenance of good air movement can also be said to be an essential component of the culture of these plants. These plants will still respond to good light levels, although they will appreciate more shade as compared to come other oncidiums discussed on this site.

Because of their long flower scapes, an effective way of growing them is to train these around a wire hoop. In this way, the plants are still manageable, and an attractive display is created.

If you have the room, these plants make handsome additions to any collection, because of the form and size of their flowers.

BREEDING

Moir 8 notes macranthum, monachicum and orgyale have been used in breeding, macranthum in particular being widely used in the early 20th century, its genes found in many oncidiinae intergeneric hybrids today.

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