INTRODUCTION
TO THE

ONCIDIUM SECTIONS

Before looking at the Sections individually, a grouping in accordance with their cultural requirements is useful. In broad terms, it is possible to group many of the Sections of the genus with respect to their cultural requirements. It is worth remembering, however, that sometimes individual species in a Section will respond to cultural conditions differing from that required by the majority of species in that Section. The following broad cultural divisions are indicated within the genus:

1. Dry all year; some 15% of all species.

2. Moist all year (52% of all species)

(a) With cool temperatures: some 28% of all species;

(b) With higher "intermediate" temperatures approximately 24% of all species.

3. Subjected to distinct seasonal variations, some 21% of all species.

4. Variable requirements within the Sections, around 12% of all Oncidium species.

The Sections included under the above cultural groupings are as follows, A brief comment of the essential elements of the culture of each Section is also included.


1. DRY ALL YEAR


This must not be taken literally; what is meant is these plants come from habitats subjected to drought or semi desert conditions, with the plants being specially adapted to survive the greater degree of dryness. After watering the plants must be allowed to dry out. The following groupings are listed in increasing ability to survive dry habitats.

1.1 Oncidium Section ((equitants, variegata) now known as Tolumnias) oncidiums are small and compact, producing a fan of generally triangular shaped leaves. Flowers are relatively small and brightly coloured, being generally long lasting. Depending on the classification used, there are around 25 to 35 species in this complex, all of which are natives of the Carribean Islands. They generally require intermediate temperatures, although they can be grown cooler during the winter if they are kept drier. The growing media must drain well, aerate well, keep free from scum and fungus, and dry well between waterings. The environment must provide good air movement. These requirements are applicable to all the plants from dry environments.

1.2 Onusta, a Section with one species native of Peru and the coastal deserts of Ecuador, where it grows on cacti.

1.3 Cebolletae, with 10 species. Plants are immediately recognisable by their terete (rounded) leaves, a water conservation adaptation to hot dry environments. Additionally, their metabolism has become adapted primarily to conserve water which would otherwise be lost during daytime respiration. These plants, like some cacti and other desert plants, respire at night when lower temperatures and higher humidity do not cause water stress. They are able to then absorb and store carbon dioxide, which is used during daylight hours for photosynthesis. For success, these plants need bright light and marked day/night temperature variations. A very open media is necessary which must dry between waterings, slab mounting often being best. Intermediate to warm conditions are appropriate.

1.4 Plurituberculata (Miltoniastrum). The "burro" or "mule eared" oncidiums comprise some 19 species.

These plants are characterised by having heavy flat leathery leaves, distinctively folded lengthwise into an open "V" shape, and which produce a spectacular display of long-lived flowers. Able to survive extremely hot and dry habitats, they require diurnal temperature variations, strong light (full sun) in intermediate to warrn temperatures.

2. MOIST ALL YEAR


This second grouping of plants is in growth all year, and accordingly must be watered all year, although this may be reduced when growth slows during the winter. Those requiring COOL temperatures (7-10 °C) are generally high altitude plants which are subjected to cool misting precipitation with daily heavy rains, without significant temperature variations, and where air movement is constant. The species in this grouping generally appreciate conditions appropriate for odontoglossums. There are some lower altitude plants requiring warmer conditions, intermediate 12-15 °C temperatures generally being appropriate for these.


2a. MOIST ALL YEAR: COOL (7 - 10°C) temperatures

2.1 Cyrtochilum Section, containing some 50 odd species, is the largest Section of the genus. Large spectacular flowers are produced, which are characterised by somewhat fleshy sepals and petals

2.2 Cimicifera Species (21) have small to minute flowers, which are inconspicuous on the plants.

2.3 Serpentia, with 3-4 species, produce a long slender wiry twining rhizome (now known in fact to be an inflorescence) from which plantlets are produced, which have 1-2 30 mm flowers.

2.4 Rostrata Section containing 27 species, are generally compact growers with free flowering characteristics.

2.5 Paucituberculata, with 9 species, have plants with minute flowers, which are comparatively unattractive.

2.6 Cucullata is a somewhat confused Section now containing some 19 species. Some botanists list few species, but with some species containing a number of named forms - 8 for example being listed for olivaceum. In the main these species are relatively small compact growers producing colourful flowers which last a long time in perfection. These species can flower themselves to death, therefore spikes should be removed early, at least until the plants are well established under cultivation.

2b. MOIST ALL YEAR: INTERMEDIATE (12 - 15 °C) growing


A number of constant moisture requiring species come from lower altitudes requiring some additional warmth, up to intermediate temperatures.

2. 7 Disticha, with one species crista-galli, is widespread from Mexico to Ecuador and Peru.

2.8 Glanduligera with 3 - 4 species produce spectacular, attractive, "butterfly" like flowers. From a wide geographical range from the Caribbean, Central and South America, they require some warmth and good light.

2.9 Stellata has flowers giving the appearance of a 5 pointed star; includes 13 species, which are described as "neat and pleasing".

2.10 Barbata, with 13 species, produce short racemes of flowers in great abundance from compact plants. ~

2.11 Oblongata with 31 species, are cool to intermediate growing, the flower spikes taking 6 - 9 months from appearance to blooming. Vigorous growers, they are also free flowering. Hoop training of their long inflorescences keeps them manageable.

2.12 Planifolia, with 32 species, are largish free growing and flowering plants.

3. SEASONAL DRY/MOIST ENVIRONMENT


Plants from this grouping (characteristically from the Organ Mountains of Brazil) are subject to significant seasonal variation. Winters are cool and bright, and the plants are dormant. With spring rains, new growths are broken, and warm temperatures are experienced. With summer sun, bright conditions are present, although some shade is provided by constant mists and appearance of foliage on the deciduous trees. The cool dry conditions must be provided when dormant, warm wet when active growth is apparent for success with these plants to be ensured. Some species have an extensive root run, and slab mounting is often the most appropriate.

3.1 Pulvinata, with 5 species. Compact medium sized growers, they produce long lasting flowers.

3.2 Waluewa, with 20 species, are compact growers, free flowering, and appreciate a long root run, preferring a slab to a pot.

3.3 Rhinocerotes, with 3 species, are distinctive as the disc of the lip has a long upward curving terete horn, like the horn of a rhinoceros. These are compact plants which put on a good display.

3.4 Concoloria, with 10 species, are modest in size, producing medium to large flowers.

3.5 Crispa species produce large flowers which last well. They are natives of Brazil, coming from moderate altitude habitats. Some 18 species make up this Section. Quite large plants, they produce a great display when well grown.

3.6 Synsepala (Varicosa) Section with 26 species produce a long lasting colourful display. Bright light is important for strong growth and maximum flowering.

3.7 Verrucituberculata, 7 species, containing some pretty medium sized flowers which can produce an attractive display at various times of the year.

4. VARIABLE REQUIREMENTS

The species in some sections have differing requirements, not fitting in with above groupings. Experimentation, ascertaining natural habitats and observation of growth patterns should enable the constituent species requirements to be ascertained.

4.1 Heterantha, with 24 species, is characterised by an "S" shaped column, and by normally developed flowers mixed with aborted star shaped ones comprising the linear segments only on the same inflorescence. Not widely grown OI known, they are of South American origin, the species requiring cool to intermediate conditions.

4.2 Planilabria Section with 16 species, are not commonly grown, the descriptions indicating a variable grouping of plants, cool to warm growing.

4.3 Excavata, with 9 species, produce colourful displays, some species being compact growers, others more robust. Temperature requirements vary, some cool to intermediate, some needing warm temperatures.

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

Good luck and good growing.

   
   
 


Click above graphic to see list of societies in your area.

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