The Oncidium Section OBLONGAGA

This Section is a quite large one containing some 31 species. Plants of this group also have conspicuous pseudobulbs. It produces bracts which are inconspicuous, being many times shorter than the stalk and ovary of the flower. The petals and sepals are somewhat similar, the lateral sepals are free, shorter than the lip. The disc of the lip bears an uneven number of tubercules without accessory protuberances. The rostellum is short.2

The species included in this Section are ampliatum, antioquiense, cabagrae, caminiophorum, caucanum, chrysomorphum, citrinum, cogniauxianum, dichromaticum, drepanopterum, floridanum, gyrobulbon, hieroglyphicum, isthmii, lentiginosum, leucochilum, maizaefolium, massangei, mathieuanum, nebulosum, oblongatum, orthostates, pardalis, reflexum reichenbahii, schilleranum, sessile, tectum, tetra- skelidion, tigrinum and volvox.2

The type species of this Section is tigrinum 2 described as one of the most beautiful and free blooming of the large flowered yellow oncidiums. It produces branching panicles of flowers during the dull months of autumn and winter, which greatly enhances its value, and it lasts six weeks in bloom.7 Its pseudobulbs are rather globular and compressed, being some 75 to 100 mm in diameter. There are two to three leaves 225 to 300 mm long, folded at the base, rather leathery in texture. The inflorescence is stout, usually erect, to 1 metre tall, loosely panieled, rather many flowered. Individual. flowers are about 75 mm long, long lasting, the sepals and petals bright yellow, more or less heavily blotched with rich brown. The lip is large, spreading, vivid yellow, sometimes with a brownish suffusion on the broad isthmus. Autumn-winter flowering, it is native of Mexico.1 It has been in cultivation since 1840, and is a cooler growing species.6

Oncidium tigrinum

In hybridisation, this species has been used with considerable success, especially in intergeneric breeding with odontoglossums and also with oncidium species, and it is said to impart vigour, large lip size and excellent spikeg.31

The other important species of this section is leucochilum, a desirable and beautiful species, of which there are many varieties, some richer in colour than others. It blooms at different times of the year, and lasts a long time in perfections. produces clustered, rather compressed pseudobulbs, ribbed with age, some 75 to 125 mm long. The normally two leaves are 200 to 300 mm long. The inflorescence is 1.6 to 4 metres long, very profusely branched, almost from its base, the slender branches few to many flowered. The flowers are waxy, long lasting, variable in size and dimensions, to more than 30 mm long. The sepals and petals are usually pale yellowish-green, more or less densely covered with confluent greenish-brown to rich brown-purple bars. The ornate. lip is mostly white. It is native of Mexico, Guatemala and Honduras.1 Cultivated since 1840, and there are a number of varieties flower spikes can take some time (sometimes up to nine months) to fully develop. This species has also been used in breeding, being an important source of dark colour inheritance as well as fine inflorescence habit. It is a vigorous grower, and free flowering under proper conditions, although Carpenter notes it seldom breeds as a female parent.31 Moir 8 believes tigrinum, oblongatum, and isthmii are most useful in the breeding of large flowered intergenerics.

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