GENERAL ONCIDIUM
CULTURAL REQUIREMENTS

In the introduction, and more specifically in the main part of this work, the cultural needs relevant to the plants in each Section have been detailed. There are, however, a number of general aspects which warrant further consideration, and these aspects are covered here.


1. AIR MOVEMENT

If there is one factor emphasised by those who have studied oncidiums in their natural habitats it is the presence of constant air movement. A constant but gentle flow of air should be maintained at all times. Experience indicates this facilitates maximum growth and also eliminates many bacterial and fungal rots which can become established where stagnant cool air exists. In a glasshouse, the running of a fan, especially at night, but preferably during the whole 24 hours, is highly recommended.


2. GROWING MEDIA

Most of the species and hybrids require free drainage to be provided, being highly intolerant of stale conditions around their roots. Always look at the roots of a plant. If they are healthy and growing strongly (white, with green growing tips), the plant will usually be doing well. If, however, the roots are brown and soft, looking unhealthy, or dying, or not growing as one would expect, look closely at the potting mix as it will probably require replacement, although other aspects of the culture should also be investigated.


The actual growing media and METHOD will vary depending on the cultural groupings indicated earlier. Both POT and SLAB culture are suitable. For growing in POTS, both clay and plastic containers can be used, but ensureplentyof drainage holes are provided. Extra drainage may be created by chipping a clay pot, or by drilling, or preferably, melting with a hot iron extra holes in plastic containers. The use of baskets is another successful adaptation of pot culture.


Chopped pine bark with or without the addition of scoria or pumice is a good relatively cheap medium for pot culture. Because of the needs of different plants from each Section, the sieving of the mix into fine, medium and coarse components is desirable. Recombine these in accordance with the requirements of each plant. For those adapted to dry conditions, use of a coarse media is appropriate. For those subjected to a seasonal climate, and most species, a medium-coarse mixture (5 - 15 mm pieces) is required. Those higher altitude plants requiring constant moisture, and especially for those with fine roots, a fine-medium mix should be formulated. Those moisture-loving plants may also appreciate the inclusion of some sphagnum moss (10-20%), although you should watch this material carefully, as it can quickly break down, making conditions unsatisfactory, especially where a high fertilising regime is followed.


With all mix formulations, the size of the plants and containers, growing facilities, humidity control and watering habits of the grower influences the final mixture.


When bark mixes are used, soak it for several days in water before use, perhaps with some nitrogen fertiliser. Allow it to dry before use, as a wet mix cannot 'flow' around the roots during repotting. Generally, bark mixes will remain in a satisfactory condition for 2 - 3 years.


An alternative to pot culture is SLAB MOUNTING. This has the advantage of producing variation in a collection. More importantly, however, is the fact that many oncidiums readily appreciate this form of growing; better drainage is provided and as the roots can be seen, more responsive cultural management is possible.


Suitable mounts are pieces of cork bark or cork branches, thin slabs of tree fern (especially that from Dicksonia fibrosa when this can be legally obtained), suitable pieces of driftwood or tree branches (citrus, manuka), or even sheets of foam plastic or similar. Generally, slab mounting is best where a reasonable level of humidity can be maintained in the growing area, either by way of watering and dampening down, or by a fine misting water spray being blown over and around the plants, ideally controlled by a humidistat. Maintenance of higher humidity is especially important during the period of establishment of the plant on the mount. A number of methods are available to secure the plant :

i) A cut can be made in the mount, the plant carefully wedged into this;

      ii) Usually the plant is tied on by

      a) Thin monofilament fishing line or

      b) Thin copper or plastic covered (black) wire or

      c) A piece of nylon stocking.

A pad of sphagnum moss, both over and under the roots, can aid establishment by providing local moisture and humidity. As this moss can rapidly break down, its careful removal after some 3 - 9 months is applicable once the new root system has developed. At that time the plant can generally remain for some years until the mount rots or breaks down.


When a plant is being secured, consider the growth habit of the plant involved. Some plants require a long root run (e.g. those from the Crispa Section, and the plant should be placed at the top of the mount to allow for this. Other plants (e.g. flexuosum Synsepala Section) have pseudobulbs distant on the rhizome. These should be placed lower on the mount, to allow for the upward growth of the rhizome. A bit of forethought at this time of mounting can save problems later.


3. REPOTTING

This will be required when:

a) The potting mix or mount has broken down;

b) The plant has grown too big.

All repotting should take place just as new growth commences, usually in the spring. Plants should be divided providing flowering divisions of at least three back bulbs plus growths. Old back bulbs can be separately potted into small containers, or placed in sphagnum moss in a closed plastic bag, and will often break into growth in three months, being potted up once new roots have developed. Do not forget to re-label all repotted plants and divisions—a plant without a name looses much of its value.

After repotting, keep plants in a warm shaded position. Reduce watering until root growth is apparent—perhaps just misting the foliage daily.


4. FERTILISERS

As applies with most orchids, a regime of fertiliser application is appropriate—a little and often being most appropriate. Apply at the rate of 1/3 to 1/2 of the manufacturer's general recommendation. Pine bark mixes require high nitrogen fertilisers, and such fertilisers should be applied all year, with higher nitrogen ratios during periods of vegetative growth. Reduce nitrogen on maturity of pseudobulbs, giving higher potash during the period of flower bud initiation. Always relate fertiliser application to the actual growth rate of the plant. Most products will be suitable — use several to ensure all elements are provided. Watch with certain vigorous growing plants where l~h nitrogen applications all year may produce very large vegetative growths but few flowers.


5. PESTS AND DISEASES


These orchids are subjected to the usual orchid pests and diseases. Provided a reasonable standard of culture is maintained no particular problems should be experienced. Should difficulties arise, use accepted insecticides, fungicides etc. according to label directions, taking all usual precautions.


6. WATERING


This will vary, as noted in the discussions on each Section. Where appropriate the seasonal variations must be provided. When constant moisture is required, this mus also be maintained. For those plants from drier habitats, or hybrids species from such habitats, allow the mix or mount to dry between wet/dry cycle of say one day appropriate for the equitants, two to three the Cebolletae, some three to seven days for Plurituberculata Section plants. seasonal variations must be allowed for.


For those growing on mounts, but also for those in pots, ensure that periodically they are placed under a spray for some time in order that any salts, which have built up,are leached away.


7. LIGHT AND TEMPERATURE


These have been covered in the first part of this chapter, and in the Section discussion. Reference is made to 'cool', 'intermediate' and 'warm' temperatures. In broad terms, the day and night minimum temperatures can be summarised as follows:

 

ONCIDIUM SEASONAL CULTURE

   TEMPERATURE REQUIREMENTS FOR MAIN GROUPS  

All in degrees censius  - SHOWN - (minimuim) desirable range (maximum

SEASON 'DRY' ALL YEAR 'MOIST' ALL YEAR  SEASONALLY VARIABLE
Cool group Intermediate group
SPRING 

Day 

Night
    . 

       18 - 25 (35) 

(15) 18 - 20


   12 - 16  (20) 

(7)  8 - 10


      18 - 25   (30) 

(10) 12 - 15
       . 

        18 - 25  (30) 

(13)  15 - 18
SUMMER 

Day 

Night
       .

20 - 30  (40) 

(15) 18 - 20


     14 - 18 (20) 

( 8) 10 - 12


       18 - 25 (30) 

(10) 12 - 18


       18 - 25   (30) 

(12) 15 - 20
AUTUMN 

Day 

Nigh


        20 - 25 (30) 

(12) 15 - 18


     12 - 15 (20) 

( 5)  7 - 10


        18 - 22 (27) 

 ( 8) 10 - 15


      12 - 15 (20) 

( 8) 10 - 12
.WINTER 

Day 

Night


        18 - 20 (30) 

(10 ) 12 - 15
   . 

      12 - 15 (18 

( 5)  7 - 10


      18 - 22 (25 

( 8) 10 - 12


     10 - 15 (20) 

( 5)  7 - 10
Temperature Conversions
Enter a number in either field, then click outside the text box.
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Temperature  O F:
OC:

 

TEMPERATURE GROUPINGS

  Optimum range targets  

All in degrees Celsius  

Temperature groups WINTER  SUMMER 
.         DAY NIGHT DAY NIGHT
COOL  10-15  7-10  15-18  7-15 
INTERMEDIATE  18-20  12-15  18-25  15-18 
WARM 20-25  18-20  20-25  18-20 

These average temperatures can be departed from once experience with is gained. Most oncidiums are adaptable, appreciate minimum night temperatures 5 to 7 than adult plants. This can often be most ideally provided by way of heat).


8. OBSERVE YOUR PLANTS


The genus is diverse, and a good grower will continually look closely at'his/her plants, observing their growth. You may be surprised what they will tell you. Read all you can about them from books and magazines; the more information you can accumulate, the more success you will have. They are, however, generally very adaptable to varying standards of culture, although they will naturally show their appreciation by way of a great display of flowers when everything is to their liking.

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